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Comparison of COD removal from pharmaceutical wastewater by electrocoagulation, photoelectrocoagulation, peroxi-electrocoagulation and peroxi-photoelectrocoagulation processes

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Abstract

This work makes a comparison between electrocoagulation (EC), photoelectrocoagulation, peroxi-electrocoagulation and peroxi-photoelectrocoagulation processes to investigate the removal of chemical oxygen demand (COD) from pharmaceutical wastewater. The effects of operational parameters such as initial pH, current density, applied voltage, amount of hydrogen peroxide and electrolysis time on COD removal efficiency were investigated and the optimum operating range for each of these operating variables was experimentally determined. In electrocoagulation process, the optimum values of pH and voltage were determined to be 7 and 40 V, respectively. Desired pH and hydrogen peroxide concentration in the Fenton-based processes were found to be 3 and 300 mg/L, respectively. The amounts of COD, pH, electrical conductivity, temperature and total dissolved solids (TDS) were on-line monitored. Results indicated that under the optimum operating range for each process, the COD removal efficiency was in order of peroxi-electrocoagulation > peroxi-photoelectrocoagulation > photoelectrocoagulation>electrocoagulation. Finally, a kinetic study was carried out using the linear pseudo-second-order model and results showed that the pseudo-second-order equation provided the best correlation for the COD removal rate.

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... 5) or two-stage oxidation process (Eqs. 6−7) may occur depending on the applied voltage (Farhadi et al. 2012): ...
... First, optimal pH value is related to the electrode material in EC process. In the case of aluminum and iron electrodes, at neutral pH, the maximum COD removal efficiency has been achieved (Ammar et al. 2019;Aswathy et al. 2016;Barışçı and Turkay 2016;Bassala et al. 2017;Cheballah et al. 2015;Ehsani et al. 2020;Elazzouzi et al. 2019;Elnenay et al. 2017;Eryuruk et al. 2018;Farhadi et al. 2012;Follmann et al. 2020;Gerek et al. 2019;Gönder et al. 2017;Hendaoui et al. 2018;Pandey and Thakur 2020;Prajapati et al. 2016;Priya and Jeyanthi 2019;Verma 2017;Yavuz and Ögütveren 2018). However, some studies have reported low residual COD concentrations at slightly acid pH values (Akhtar et al. 2020;Barrera-Díaz et al. 2014;Elkacmi et al. 2020;Fajardo et al. 2015;GilPavas and Correa-Sanchez 2020;Nasrullah et al. 2019;Niazmand et al. 2019). ...
... 1-To remove the toxic constituents from some types of wastewater in addition to some non-biodegradable compounds (Bazrafshan et al. 2013;Borja et al. 1995;Capasso et al. 1995; It should be noted that EC has been used as a post treatment polishing process to achieve a higher degree of pollutants removal after the primary treatment processes (Al-Qodah et al. 2020). The performance of EC compared with that of chemical coagulation (Akyol et al. 2013;El-Ashtoukhy and Amin 2010;Farhadi et al. 2012;Ghanbari and Moradi 2015;Khataee et al. 2009;Muthukumar et al. 2010;Tchamango et al. 2016;Ye and Li 2016;Yilmaz et al. 2007;Zaleschi et al. 2013), biological treatment (Ahmad et al. 2016;Barrera-Díaz et al. 2009), anodic oxidation (El-Ashtoukhy and Amin 2010), Fenton (Akyol et al. 2013;Ghanbari and Moradi 2015;Tchamango et al. 2016), UV/nano-TiO 2 Fenton-like, and many others EF (Khataee et al. 2009) is very promising. Moreover, EC represents a promising treatment process achieving high removal efficiencies with low solid wastes. ...
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Electrocoagulation (EC) is one of the emerging technologies in water and wastewater treatment as it combines the benefits of coagulation, sedimentation, flotation and electrochemical oxidation. Extensive research efforts implementing EC technology have been executed over the last decade to treat chemical oxygen demand (COD) rich industrial wastewaters with the aim to protect pollution of freshwater streams (e.g., rivers, lakes etc.). Accordingly, the primary aim of this paper was to tender a comprehensive review of the available recent literature utilizing EC and provide recommendations for the future studies that can improve the EC technology and broaden its range of application. This review introduces, in the first part, the various technologies often adopted for industrial wastewater treatment compared to the application of EC as a treatment method of COD rich wastewater. EC process, amongst the various technologies practiced for treatment of COD rich industrial wastewater, has been viewed as the most privileged treatment technology by different research groups owing to its ability to treat abundant volumes of wastewater. In the second part, application of EC as a single and combined treatment method of COD rich wastewaters has been thoroughly reviewed. It can be concluded from this review paper that operational conditions of EC process at voltage of 10 V and reaction time of 60 min in the batch reactor can be the best for guaranteeing high COD removal efficiencies of > 90 %. This review also concludes that considerably large operation costs of the EC process appears to be the serious drawback and renders it as an unfeasible approach for handling of COD rich wastewaters. In the end, this review has attempted to highlights the potential and limitation of EC and suggests that vast research notably in the field of continuous flow EC system is essential to introduce this technology as a convincing wastewater technology.
... Adsorption suffers from expensive adsorbent regeneration, long treatment time, and solid disposal issues, despite being effective for treating dye-containing effluent [7]. Chemical coagulation could attain a high removal efficiency, but it produces a large quantity of subsequent wastewater, which needs further treatment leading to overall high processing cost [8]. Fenton like processes and electrocoagulation produces a significant amount of sludge and is not effective for complete degradation of dye molecules. ...
... But the high cost of membrane and equipment, fouling problems during operation, are the limitations of the membrane process [9]. Biological treatment is economical, ineffective in the treatment of refractory organic wastewater [8]. Therefore, complete destruction of dye molecules from synthetic wastewater is an urgent need considering ecology and environmental damage prevention. ...
... Besides, the conductivity of the solution increased significantly from 1452 to 3614 μS/cm, resulting in a reduction of the operating voltage from 18.1 to 7.1 V. Consequently, the electrical energy consumption reduced from 3.62 to 1.42 kWh/m 3 , and the electro-oxidation process was promoted by producing active chlorine at anode [30]. The mechanistic equations for the indirect electro-oxidation process are presented in Eq. (7)(8)(9)(10)(11) [12,34], ...
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The present study deals with the decolourization of synthetic Reactive Turquoise Blue 21 (RTB21) dye-based model wastewater using an indirect electro-oxidation process and enhanced by modified graphite electrodes. Graphene oxide (GO) was successfully synthesized and deposited on the surface of pre-treated graphite electrodes. It was further reduced to form reduced graphene oxide (rGO). The resultant newly developed anode electrodes were designated as (Gr)0, (rGO/Gr)1, and (rGO/Gr)2 and used for the treatment of wastewater. Electrodes, thus developed, were characterized using Fourier-transform infrared spectroscopy, X-ray diffractions, Field emission scanning electron microscopy, and Contact angle (CA). The effect of process parameters such as initial pH, current density, electrolyte concentration, and temperature on the performance of novel anode electrodes was investigated. The colour removal efficiency was increased significantly almost 25.80% in the presence of a modified electrode with the highest efficiencies of about 96.69% in a natural pH environment, 200 A/m², 2 g/L NaCl concentration, 30 °C temperature, and 15 min process time for 50 ppm RTB21 dye concentration for (rGO/Gr)2 electrode. The RTB21 decolourization by indirect electro-oxidation process follows the pseudo-first-order kinetics, and the activation energy was estimated to be 23.42 kJ/mol. The stability of (rGO/Gr)2 electrode was also examined. The rGO coated electrode was a superior electrode for the indirect electro-oxidation process, giving enhanced colour removal (%).
... According to Faraday's law, with increasing reaction time of EC process, the increasing amount of iron species can limit the elimination efficiency [39]. Farhadi et al. [43] studied the removal of COD from pharmaceutical wastewater and reported after 30 min reaction time, the amount of COD decreased from 330 to 311 mg/L and the efficiency increased from 31.9% to 35.9%. In addition, Bazrafshan et al. [44] demonstrated that in the first 15 min, the rapid removal efficiency obtained and finally in 75 min, approximately 92.7% removal occurred. ...
... In addition, the EC can reduce the required reaction, which ultimately leads to a reduction in energy requirement and operating cost [60,61]. Farhadi et al. [43] studied the COD removal from the pharmaceutical wastewater by electrocoagulation process and demonstrated that the EC value decreased from 1,514 to 948 µS/cm after 90 min. ...
... As can be seen from Fig. 7b, at the beginning of the PS-EC process, the pH of the solution was 7 and over reaction time, a gradual increase in pH was observed and reached to 8.27 after 90 min. Farhadi et al. [43] stated that pH control was difficult during the electrocoagulation process and the value of solution pH varied from 7 to 8.75 after 90 min reaction. ...
... They can generate highly potent oxidants in situ as OH radicals with electrical energy to deal with persistent organic pollutants, especially atrazine [9]. Electrochemical technologies have reached a promising state of development and can also be used effectively for contaminant removal [19]. Electrochemistry is a treatment related to electrical currents and chemical reactions, the conversion of chemical energy into electrical energy and in the opposite direction. ...
... In this study 20 treatments were run with different combinations for current intensitytreatment time-recirculation flow rate, a fraction of data was selected to show the circulation rate effect. Treatments 3,5,7,12,15,16,18,19, were taken (1.5 A and 135 min). It was noted that recirculation rate effect was proportional to atrazine removal in both reactors UCER and URER, the more recirculation rate produced a major atrazine removal, to mention that in UCER atrazine removal had a decrement from 65.91 mL/min to 150 mL/min and posterior increment from 150 mL/min to 234.09 mL/min. ...
... From the statistical results obtained in this research, I, t, reactor type, and the interaction between I-t (Electrical current-time) where significant models. The results are in agreement with the observed by Romero-Soto et al. [19] the authors stated that the combination of electrolysis time and the current intensity, are significant parameters in the chloramphenicol removal. ...
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In Mexico, atrazine is widely used in agriculture to control broadleaf weeds. The objective of this research was to compare atrazine removal in water and energy consumption between an up-flow cylinder electro-oxidation reactor (UCER) and an up-flow rectangular electro-oxidation reactor (URER) using the response surface methodology. In each reactor, two titanium (Ti) mesh electrodes (cathodes) and one Titanium-Lead Dioxide (Ti-PbO2) mesh electrode (anode). Current intensity effects, electrolysis treatment time, and recirculation flow were evaluated. Synthetic water with 5 mg/L atrazine content was used. Optimum atrazine removal values were obtained at 2 A electric current, 180 min of treatment time, and 200 mL/min recirculation rate for both reactors: in these conditions an atrazine removal of 77.45% and 76.89% for URER and UCER respectively. However, energy consumption showed a significant difference of 137.45 kWh/m3 for URER and 73.63 kWh/m3 for UCER. Regarding energy efficiency, a 60% atrazine removal was reached in both reactors using less energy for UCER at (1.5 A–135 min–150 mL/min–25.8 kWh/m3) and for URER at (0.66 A–135 min–150 mL/min–20.12 kWh/m3).
... Photoelectrocoagulation, peroxi-electrocoagulation, and peroxi-photoelectrocoagulation are AOPs that integrate electrocoagulation, UV light, and H 2 O 2 . These processes have been reported for the treatment of pharmaceutical wastewater [22]. In Farhadi et al. work [22], a comparison among electrocoagulation, photoelectrocoagulation, peroxielectrocoagulation, and peroxi-photoelectrocoagulation processes were investigated for the removal of chemical oxygen demand (COD) from pharmaceutical wastewater originated from the pharmaceutical company. ...
... These processes have been reported for the treatment of pharmaceutical wastewater [22]. In Farhadi et al. work [22], a comparison among electrocoagulation, photoelectrocoagulation, peroxielectrocoagulation, and peroxi-photoelectrocoagulation processes were investigated for the removal of chemical oxygen demand (COD) from pharmaceutical wastewater originated from the pharmaceutical company. In this work, the capabilities of the processes were reported up to 54.7% COD removal after 60 min of reaction. ...
... The conventional activated sludge and trickling filter methods have also been employed in the removal of pharmaceutical compounds from wastewater, though it is not as successful [13]. Moreover, the biological methods are a cost-effective process but they are not as effective in stubborn carbon-based pharmaceutical wastewaters [3,14]. However, the use of specialized reactor systems such as anaerobic membrane bioreactor would be the acceptable approach for the removal of organic matter. ...
... Based on the growth performance at the pilot level study, they scale up the process up to HRAP (300,000 L) to ensure the scalability approach. Their investigation reported high biomass production of 0.98 ± 0.03 g/L and pollutant removal efficiencies were NH 4 + (~100%), 14 were removed from the aqueous phase above 50%, and 07 were removed ~90% of their initial concentrations. Moreover, 6 days of HRAP treatment successfully removed 69% of the studied pharmaceutical ingredients (25 of 36 studied). ...
Article
Wastewater contains a munificent range of hazardous pollutants such as pharmaceuticals, and xenobiotics. Among them, ~79 types of different pharmaceuticals, and xenobiotics have been reported to exist in wastewater and were not effectively removed through the conventional wastewater treatment system. Recently, with increasing socioeconomic aspects and environmental awareness, societies are more alert and are trying to search for possible solutions to treat these polluted wastewaters. Thus, microalgae-based treatment systems are a promising way to remediate pharmaceuticals or xenobiotics wastewater partially (8–70%). However, some of the antibiotics at low concentrations (7.5 ng/L–500 μg/L) especially sulfa groups, oxytetracycline, erythromycin, pharmaceutical drugs, and growth hormones are toxic to the algal cells. Advancements in the microalgal treatment systems and optimization of growth conditions have increased the removal efficiency up to 85–99%. However, it depends on concentrations and types of microalga species. Thus, the review highlights the potential use of microalgae for pharmaceutical contaminants removal from wastewater and their mechanism. Moreover, the role of enzymes, the interaction of microalgal EPS, and the toxicity of pharmaceutical contaminants in microalgae are critically discussed. The current review briefly deliberates various factors affecting the growth of microalgae in the wastewater treatment process. Additionally, it critically discusses the different microalgae-based advancements in the treatment of pharmaceutical wastewater such as consortia and immobilization. In addition, it has disparagingly summarized the recent pilot-level study and reflected upon the published data highlighting the utilization of pharmaceutical and xenobiotic treated algal biomass into biofuels. Moreover, the challenges and conceptual integrated approach of the microalgae-based treatment process to maintain environmental sustainability has been elaborated in terms of circular bioeconomy.
... Photoelectrocoagulation, peroxi-electrocoagulation, and peroxi-photoelectrocoagulation are AOPs that integrate electrocoagulation, UV light, and H 2 O 2 . These processes have been reported for the treatment of pharmaceutical wastewater [22]. In Farhadi et al. work [22], a comparison among electrocoagulation, photoelectrocoagulation, peroxielectrocoagulation, and peroxi-photoelectrocoagulation processes were investigated for the removal of chemical oxygen demand (COD) from pharmaceutical wastewater originated from the pharmaceutical company. ...
... These processes have been reported for the treatment of pharmaceutical wastewater [22]. In Farhadi et al. work [22], a comparison among electrocoagulation, photoelectrocoagulation, peroxielectrocoagulation, and peroxi-photoelectrocoagulation processes were investigated for the removal of chemical oxygen demand (COD) from pharmaceutical wastewater originated from the pharmaceutical company. In this work, the capabilities of the processes were reported up to 54.7% COD removal after 60 min of reaction. ...
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This study evaluates the performance of photoelectrocoagulation, peroxi-electrocoagulation, and peroxi-photoelectrocoagulation for the removal of the antiviral drug lamivudine formulation from wastewater by a stainless-steel electrode. To investigate matrix effects for this oxidation process, the influence of substrates such as urea and simulated wastewater (SWW) was studied. Moreover, degradation kinetics and energy efficiency are also discussed. Results indicate that the removal efficiency was in the order of peroxi-photoelectrocoagulation > peroxi-photoelectrocoagulation (in the presence of urea) > peroxi-photoelectrocoagulation (in the presence of SWW) > peroxi-electrocoagulation > photoelectrocoagulation. In peroxi-photoelectrocoagulation, the 96% degradation of lamivudine formulation indicates a nearly complete degradation of lamivudine. In this process, the presence of urea and SWW resulted in a substantial reduction of chemical oxygen demand (COD) decay. Kinetic studies using linear pseudo-first and pseudo-second-order reaction kinetics showed that the pseudo-first-order equation effectively described the removal of lamivudine formulation. The highest energy consumption per kgCOD decay (i.e., kWh kgCOD− 1) was obtained for the photoelectrocoagulation process, while the lowest energy consumption was obtained for peroxi-electrocoagulation, for all electrolysis times. The peroxi-photoelectrocoagulation process was shown to be an effective and energy-efficient technique for removing the antiviral drug lamivudine formulation from wastewater. Graphic abstract
... Pharmaceutical wastewater includes different chemical compounds and functional groups, which inhibit microbial activity [21,22]. This characteristic makes it unfit for biological treatment. ...
... In addition, using high CD, much of the energy is lost in the water electrolysis reaction and heating due to the joule effect. Therefore, it is crucial to operating the device at an optimum CD [21]. For removing oxytetracycline hydrochloride, Nariyan et al. (2017) reported that the optimum current density was 20 mA.cm −2 using Fe/Al [134]. ...
Article
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Increasing dependency on pharmaceutical compounds including antibiotics, analgesics, antidepressants, and other drugs has threatened the environment as well as human health. Their occurrence, transformation, and fate in the environment are causing significant concerns. Several existing treatment technologies are there with their pros and cons for the treatment of pharmaceutical wastewater (PWW). Still, electrocoagulation is considered as the modern and decisive technology for treatment. In the EC process, utilizing electricity (AC/DC) and electrodes, contaminants become coagulated with the metal hydroxide and are separated by co-precipitation. The main mechanism is charge neutralization and adsorption of contaminants on the generated flocs. The range of parameters affects the EC process and is directly related to the removal efficiency and its overall operational cost. This process only could be scaled up on the industrial level if process parameters become optimized and energy consumption is reduced. Unfortunately, the removal mechanism of particular pharmaceuticals and complex physiochemical phenomena involved in this process are not fully understood. For this reason, further research and reviews are required to fill the knowledge gap. This review discusses the use of EC for removing pharmaceuticals and focuses on removal mechanism and process parameters, the cost assessment, and the challenges involved in mitigation.
... − 1 ). At higher current density, the rate of anodic metal dissolution increases that brings a greater amount of metal hydroxide flocs for pollutant removal (Bayar et al., 2011;Can and Bayramoglu, 2010;Farhadi et al., 2012). Also, at high current density, electro-flotation dominates over precipitation, while at low current density, precipitation or sedimentation dominates over flotation. ...
... pH is one of the most important parameters affecting the conductivity of the solution, contaminant distribution, zeta potential of charged particles, ionic characteristic of the organic molecules, electrode dissolution, and concentration of gas bubbles (Garcia-Segura et al., 2017;Shamaei et al., 2018;Thirugnanasambandham et al., 2016). It also governs the formation of hydrolyzed metal species and hence determines the coagulation mechanism (Farhadi et al., 2012;Garcia-Segura et al., 2017;Katal and Pahlavanzadeh, 2011). During EC, the pH of the solution changes to the neutral range (around 6-8) depending on the electrode material and initial pH (Al Aji et al., 2012;Can and Bayramoglu, 2010;Elabbas et al., 2016). ...
Article
Over the last few decades, water pollution has become a major concern considering the adverse impact on environment and human health. Several methods and strategies have been investigated to the treatment of wastewater. Because of the introduction of more stringent pollution regulations and for sustainable development, recently EC has been shown as an emerging and alternative process to treat different types of wastewaters. This study represents a comprehensive review of reaction mechanisms for pollutants removal along with the operating parameters that need to be addressed for optimum application. The study demonstrated that the process has been applied effectively for the treatment of different types of industrial wastewaters as well as municipal and potable waters. In the case of treating highly contaminated wastewater, EC process is effective when it is used in combination with biological and/or other processes, and this combined treatment system can be considered as a potential treatment technology for recycling and reuse of effluents from diverse sources. This review also represents technological aspects of conversion of electrocoagulated sludge to valuable resources, H2 recovery, and the application of solar energy as an alternative source of electrical energy to apply the EC process more sustainably. Finally, this review highlighted some limitations with recommendations for promising research options that can make this technology more feasible for industrial applications.
... (fiG. 3) produces wastewater with a high chemical oxygen demand (up to 28,640 mg l -1 ) and comparatively low biochemical oxygen demand and low inorganic contaminants 122,123 . Using biochar as an adsorbent for organic pollutants can be part of the solution for pharmaceutical wastewater treatment 124 . ...
Article
Biochar, a carbon-rich material made from the partial combustion of biomass wastes, is an emerging material of interest as it can remediate pollutants and serve as a negative carbon emission technology. In this Review, we discuss the application of biochar in municipal wastewater treatment, industrial wastewater decontamination and stormwater management in the context of sustainable development. By customizing the biomass feedstock type and pyrolysis conditions, biochar can be engineered to have distinct surface physicochemical properties to make it more efficient at targeting priority contaminants in industrial wastewater treatment via adsorption, precipitation, surface redox reactions and catalytic degradation processes. Biochar enhances flocculation, dewatering, adsorption and oxidation processes during municipal wastewater treatment, which in turn aids sludge management, odour mitigation and nutrient recovery. The addition of biochar to sustainable drainage systems decreases potential stormwater impact by improving the structure, erosion resistance, water retention capacity and hydraulic conductivity of soils as well as removing pollutants. The feasibility of scaling up engineered biochar production with versatile, application-oriented functionalities must be investigated in collaboration with multidisciplinary stakeholders to maximize the environmental, societal and economic benefits. Biochar is a promising negative carbon emission technology with applications in wastewater pollution control. This Review assesses the performance of engineered biochar in various industrial, municipal and stormwater treatments, and discusses the partnerships required for biochar commercialization. Biochar, a type of partially combusted biomass, is a promising and carbon-negative solution for municipal and industrial wastewater treatment and stormwater management, as it can remove up to four times its own weight in carbon.Biochar performance in the water–climate–energy nexus is governed by its properties, which can be engineered for different purposes during biomass feedstock selection and customized production. Mineral-rich biomass can produce biochar with higher nutrient and ash contents, whereas lignin- and cellulose-rich biomass can form biochar with higher aromatic carbon contents.Multifunctional biochar can enhance sludge settleability, boost biological treatment and close resource loops by using sludge as feedstocks in municipal wastewater treatment.Specific removal strategies, including precipitation, sorption and catalytic degradation, with appropriate design of engineered biochar, are needed for industry-specific wastewater treatment to target various pollutants and aquatic chemistry.Engineered biochar can accelerate the attainment and harness the synergy of at least 11 of the 17 Sustainable Development Goals throughout the cradle-to-grave life cycle.Partnership among interdisciplinary stakeholders, with strong policy support, a science-informed standardization system and state-of-the-art research advances, is the key to commercializing biochar for large-scale applications. Biochar, a type of partially combusted biomass, is a promising and carbon-negative solution for municipal and industrial wastewater treatment and stormwater management, as it can remove up to four times its own weight in carbon. Biochar performance in the water–climate–energy nexus is governed by its properties, which can be engineered for different purposes during biomass feedstock selection and customized production. Mineral-rich biomass can produce biochar with higher nutrient and ash contents, whereas lignin- and cellulose-rich biomass can form biochar with higher aromatic carbon contents. Multifunctional biochar can enhance sludge settleability, boost biological treatment and close resource loops by using sludge as feedstocks in municipal wastewater treatment. Specific removal strategies, including precipitation, sorption and catalytic degradation, with appropriate design of engineered biochar, are needed for industry-specific wastewater treatment to target various pollutants and aquatic chemistry. Engineered biochar can accelerate the attainment and harness the synergy of at least 11 of the 17 Sustainable Development Goals throughout the cradle-to-grave life cycle. Partnership among interdisciplinary stakeholders, with strong policy support, a science-informed standardization system and state-of-the-art research advances, is the key to commercializing biochar for large-scale applications.
... Biological removal methods are a cost-effective method but have little effect on resistant organic compounds. Chemical and physical treatment can produce high efficiency and produce high quality wastewater but its treatment costs are relatively high [19]. However, the adsorption method, which is a physical method, is one of the most widely used methods for removal of aquatic pollutant [20; 21]. ...
... Indigo occupies 7%, representing about 120,000 tons of dyes used annually [5]. Several methods have been described in the literature to remove color: adsorption [6], ion exchange, and membrane filtration [7], chemical coagulation [8], chemical and Fenton oxidation [9], among other. Some of those methods are costly and less effective. ...
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Zinc oxide is a useful and recyclable catalyst. In this study, fique fibers were modified with zinc oxide (ZnO) nanoparticles to remove color from indigo carmine (IC) solutions. ZnO nanoparticles were synthesized by precipitation method and the fibers were ex-situ and in-situ modified. The fibers and the nanoparticles were characterized using different techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–visible spectroscopy and Scanning Electron Microscopy (SEM). The color removal rate was monitored by using an UV/Vis spectrophotometer. Nanoparticles with a mean diameter in the nanoscale and a typical hexagonal structure were obtained, and they were effectively deposited on the fibers. The highest color removal was obtained with the ex-situ fibers (ZnO-Ex/fique) 90 % in 180 minutes. Color removal by in-situ fibers (ZnO-In/fique) was 70 % after 180 min. From the results, ZnO nanoparticles may be an excellent catalyst for removal IC dye aqueous solutions under UV-C light.
... and Al-Shannag 2019; Gilpavas et al. 2019). The most studied AEPs are the sono-electrocoagulation (combination of ultrasonic radiation with EC, Sono-EC) (He et al. 2016;Raschitor et al. 2020), the combination of ozone (O 3 ) with electrocoagulation (O 3 -EC) (Behin et al. 2015;Bili et al. 2019), the electrocoagulation assisted by the addition of hydrogen peroxide (H 2 O 2 ) known as peroxi-electrocoagulation (peroxi-EC) (Barrera-Díaz et al. 2008;Nasrullah et al. 2017), assisted electrocoagulation with UV irradiation or photo-electrocoagulation (Photo-EC) (Cotillas et al. 2014a;Medel et al. 2019), and the simultaneous implementation with UV irradiation and addition of H 2 O 2 called photoperoxi-electrocoagulation (Farhadi et al. 2012;Borba et al. 2018). ...
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Photo-electrocoagulation with aluminum electrodes is becoming an increasingly attractive process for the degradation of organic pollutants in low concentration levels, such as those found in secondary effluents (biological processes). The technological potential of this approach relies on the synergistic effect of the electrochemical generation of coagulants, active chlorine species, and photochemical reactions promoted by UV irradiation (λ = 254 nm) which results in the formation of highly reactive oxygen species such as the ·OH radical. In this context, the goal of this work was to demonstrate and evaluate the influence of the operating parameters of a laboratory-scale photo-electrocoagulation process on the generation of ·OH radicals. Using fluorescence spectrophotometry, it was possible to detect and quantify ·OH radicals by means of coumarin and terephthalic acid assessment. The production of ·OH radicals was highly influenced by the pH of the solution, observing the highest concentration at pH 3. Chloride concentration also showed a positive effect on the generation of ·OH radicals; however, this influence was only observed up to a chloride ion concentration of 30 mM. In addition, phenol mineralization of 20.1% was achieved by applying a current density of 2.7 mA cm−2 under 2 h of irradiation. To the best of our knowledge, this is the first study that demonstrates the production of ·OH radicals in a photo-electrocoagulation process with aluminum electrodes.
... Chemical and physical treatments, however, are highly efficient and can produce high-quality effluent; yet, they are also very costly. Thus, researchers are searching for a more appropriate treatment method for pharmaceutical wastewater treatment (Farhadi et al., 2012;Samadi et al., 2015). The photocatalytic process has been regarded as an efficient removal process recently (Xue et al., 2015;Zhou et al., 2018). ...
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Ciprofloxacin antibiotic that is used to cure several kinds of bacterial infections have a high solubility capacity in water. The influent of ciprofloxacin to water resources in a low concentration affect the photosynthesis of plants, transforms the morphological structure of the algae, and then disrupts the aquatic ecosystem. 75% of this compound is excreted from the body down to the wastewater which should be removed. BiFeO3 , a bismuth based semiconductor photocatalyst that is responsive to visible light, has been recently used to remove organic pollutants from water. In this study, the optimal conditions for removing ciprofloxacin from aqueous solutions by the BiFeO3 process were investigated. Effective parameters namely pH, reaction time, ciprofloxacin initial concentration, BiFeO3 dose, and temperature on ciprofloxacin removal were studied by using response surface methodology. The validity and adequacy of the proposed model was confirmed by the corresponding statistics (i.e. F-values of 14.79 and 1.67 and p-values of <0.0001 and 0.2505 for the own model and its lack of fit, respectively, R2 = 0.9107, R2 adjusted = 0.8492, R2 predicted = 0.70, AP = 16.761). Hence the Ciprofloxacin removal efficiency reached 100% in the best condition (pH 6, initial concentration of 1 mg/L, BiFeO3 dosage of 2.5 g/L, reaction temperature of 30° C, and process time of 46 min).
... Also, the metal hydroxides with the formation of flocs remove organic compounds and colloidal particles. Finally, the formed flocs remove easily from aqueous solution by sedimentation or flotation (Farhadi et al. 2012). Higher pH value improves the ozone decomposition to generate higher OH · radicals, which this phenomenon leads to effective oxidation of organic compounds; thus a higher COD removal was achieved (Yang et al. 2012). ...
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Cardboard factory wastewater is usually known by high chemical oxygen demand (COD), color, phenols, lignin, and its derivatives, and usual treatment techniques are not able to treat such wastewaters. This study aimed to investigate the efficiency of ozone-assisted electrocoagulation process (EC/O3) for the treatment of real cardboard wastewater. The parameters influencing COD removal in the EC/O3 process were optimized using response surface methodology. Regard to the statistical model, the optimum conditions were obtained at current density 9.6 mA/cm², time 20 min, and pH 12. At optimal condition, EC/O3 process removed 74.7% and 97.5% of COD and color, which was higher compared to ozonation and EC processes separately. The COD removal followed pseudo-first-order kinetic with the coefficient correlation of 0.97 and the reaction rate constant of 0.073 1/min. To sum up, the combined electrocoagulation process with ozonation could be used satisfactorily for removing pollutants from real cardboard wastewater.
... The reaction time controls the generation rate of Fe 2+ or Fe 3+ ions emitted from the stainless-steel electrodes. The concentration of hydroxide ions and metals produced on the electrodes directly affects the removal efficiency [47]. The operating time has been changed within the range of 5 to 60 minutes to examine its effect on the removal efficiency, with the other experimental conditions remaining constant. ...
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For this research, the utilisation of electrocoagulation (EC) tore-move theciprofloxacin (CIP) and levofloxacin (LVX) from aqueous solutions was examined. The effective removal efficiencies are 93.47% for CIP and 88.00% for LVX, under optimum conditions. The adsorption isotherm models with suitable mechanisms were applied to determine the elimination of CIP and LVX utilizingtheEC method. Thefindingsshowed the adsorption of CIP and LVX on iron hydroxide flocs followed the Sips isotherm, with correlation coefficient values (R 2) of 0.939 and 0.937. Threekinetic models were reviewed to determine the accurate CIP and LVX elimination methods using the EC method. The results showed that itfittedfor the second-order model, which indicated that the chemical adsorp-tion mechanism controlled the removal of CIP and LVX. The R 2 with CIP is 0.944, and LVX is 0.941. For binary system removal, efficiencies were 93.00, 90.10, and 96.30% for CIP, and 91.80, 96.10, and 92.97% for LVX, at the CIP ratio: LVX of 1:1, 1:4, and 4:1. The electrode consumption (ELC) and electrical energy consumption (EEC) were found at 0.208 g and 3.21 kWh −3 for a single operation. The operating cost was estimated at 0.613 US$ m −3. ARTICLE HISTORY
... Moreover, Fe(II) can be regenerated by Fe(III) reduction on the cathode (Equation (4)), ensuring the continuity of the Fenton reaction (Equation (1)). This process is known as peroxyelectrocoagulation (PEC) [25][26][27]. The main reactions occurring at the oxygen/air diffusion cathode (Equations (3) and (4)) and at the Fe anode (Equation (5)) are detailed below: ...
Article
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Electro-Fenton (EF) and peroxyelectrocoagulation (PEC) processes were investigated to mineralize 10 mg L −1 erythromycin from ultrapure water, evaluating the influence of the anode material (BDD and Fe), current density (janode) (5 mA cm −2 and 10 mA cm −2), oxygen flowrate injected to the cathode (0.8 L min −1 O2 and 2.0 L min −1 O2) and pH (2.8, 5.0 and 7.0) on the process efficiency and the electricity costs. 70% mineralization was reached after applying 0.32 A h L −1 under the best operational conditions: PEC treatment at 5 mA cm −2 , 2.0 L min −1 O2 and pH 2.8. The electricity consumption of the electrochemical cell under these conditions was approximately 0.3 kWh m −3. Early-stage intermediates produced from erythromycin degradation were identified and quantified throughout the treatment and a potential erythromycin degradation pathway was proposed. The most appropriate operational conditions tested with synthetic solutions were applied to treat a real effluent from the tertiary treatment of an urban wastewater treatment plant. All emerging compounds listed in the EU Decision 2018/840 (Watch List 2018) were determined before and after the PEC treatment. All listed pollutants were degraded below their quantification limit, except estrone and 17-α-ethinylestradiol which were 99% removed from water. Electricity consumption of the elec-trochemical cell was 0.4 kWh m −3. Whilst awaiting future results that demonstrate the innocuity of the generated byproducts, the results of this investigation (high removal yields for emerging pollutants together with the low electricity consumption of the cell) indicate the promising high potential of PEC treatment as a water treatment/remediation/regeneration technology.
... Numerous researchers have reported efficient hybrid processes for the removal of azo dyes and antibiotics (Chaabane et al. 2013;Farhadi et al. 2012;Sirés and Brillas 2012;Wei et al. 2012). Chaabane et al. (2013) reported the treatment of pharmaceutical and hospital effluent using new hybrid techniques, which coupled sequential operations. ...
Article
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The toxicity of pharmaceutical pollutants affects aquatic life as well as the environment on all levels of the natural hierarchy. Therefore, to maintain the natural environment it is crucial to exclude pharmaceutical compounds, such as ofloxacin (OFX), sunset yellow (SY), and tartrazine (TRT) from aqueous systems. In this study, a green nanoadsorbent (CS@GOn) will be prepared by the electrostatic interaction of chitosan (CS) and graphene oxide (GO). Characterization using scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), and Fourier-transform Infrared (FTIR) spectroscopy analysis of CS@GOn will be performed and the cross-linking of CS with GO will be confirmed. Further, batch electrocoagulation (EC) and ultrasonication adsorption (UA) assisted processes will be performed individually and as hybrid systems for the removal of OFX, TRT, and SY from aqueous solutions. The optimum conditions will be evaluated by considering the minimum operating cost (OC). In EC processes, based on the economic >70% removal of OFX, TRT, and SY were achieved at optimum conditions of pH 7, 10 min, and OFX 200 mg/L. However, in UA processes, >83% OFX, TRT, and SY were removed under the same conditions. In hybrid EC and UA processes, >98% OFX, TRT, and SY were removed at the optimized conditions (pH 7, 10 min, and OFX 200 mg/L, dose 0.1 g/200 mL, and 25°C). CS@GOn was reused up to five times after the regeneration. Compared with EC and UA individual processes, hybrid EC and UA processes were more effective for the removal of OFX, TRT, and SY. A feasibility study of EC + UA process will be explored for the removal of chemical oxygen demand (COD) from actual sewage effluent and 95% removal was achieved for a 10 min reaction time of EC and UA. This study provides a promising hybrid EC and UA process with CS@GOn that has excellent biocom-patibility, reusability potential, and could be used in a wide range of industrial effluents.
... Advanced oxidation processes [5][6][7], membrane processes [7][8][9], electrocoagulation [10][11][12], biodegradation [13][14][15], and adsorption [16][17][18][19] are widely used removal techniques for the pharmaceuticals from the water systems. Among these techniques, even though advanced oxidation processes are the most effective method, it has some disadvantages such as very expensive, operationally complex, intermediate products formation. ...
Article
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In this study, a novel microporous activated carbon (AC) from low-cost biomasses (apricot and peach stones, and almond shell) mixture by FeSO4 activation and following pyrolysis was synthesized, characterized, and tested for etodolac (ETD) adsorption. The characteristics of AC were determined by BET surface area, total pore volume, average pore size, surface functional group analysis by Boehm’s titration and FTIR, and SEM-EDX. A high-quality activated carbon with 958.57 m2/g surface area, 0.4796 cm3/g total pore volume, and 1.9963-nm average pore size could be successfully synthesized from the mixture activated by FeSO4 at impregnation ratio of (FeSO4/precursor (w/w)) 0.5. ETD adsorption ability of the prepared AC was investigated depending on the effects of AC dosage, contact time, pH, initial ETD concentration, and temperature. Also, the linear and nonlinear forms of Langmuir and Freundlich isotherms and pseudo-first-order and pseudo-second-order kinetic models were compared to get the best isotherm and kinetic model. The results showed that more than 95% ETD adsorption could be achieved at the presence of 5 g/L of AC, contact time of 150 min, and at a wide pH range. The adsorption data was found to be best fitted to the nonlinear pseudo-second-order kinetic model and nonlinear Freundlich isotherm. The adsorption of ETD onto the AC was found to be exothermic and spontaneous.
... The combination of electrochemistry with the photo (UV) is a hybrid technique for the removal of recalcitrant compounds from wastewater [27]. The peroxi-photoelectrocoagulation process is one of the electrochemical processes that was investigated for the removal of COD from pharmaceutical wastewater in a few studies [28,29]. The major parameters affecting the effectiveness of this process are the operating conditions such as the initial COD, pH, reaction time, current density, anode materials, and electrolyte concentration [30][31][32]. ...
Article
The peroxi-photoelectrocoagulation process was evaluated for the removal of chemical oxygen demand (COD) and color from healthcare wastewater. A 2-level full factorial design with center points was created to investigate the effect of the process parameters, i.e., initial COD, H2O2, pH, reaction time and current density. Furthermore, the total energy consumption and average current efficiency in the system were evaluated. Predictive models for % COD, % color removal and energy consumption were obtained. The initial COD and pH were found to be the most significant variables in the reduction of COD and color in peroxi-photoelectrocoagulation process. Hydrogen peroxide only has a significant effect on the treated wastewater when combined with other input variables in the process like pH, reaction time and current density. In the peroxi-photoelectrocoagulation process, current density appears not as a single effect but rather as an interaction effect with H2O2 in reducing COD and color. Lower energy expenditure was observed at higher initial COD, shorter reaction time and lower current density. The average current efficiency was found as low as 13 % and as high as 777 %. Overall, the study showed that hybrid electrochemical oxidation can be applied effectively and efficiently for the removal of pollutants from healthcare wastewater.
... Overall, the addition of H 2 O 2 resulted in a total COD removal of 85% (residual 12,000 mg/L) and color removal of 100% with energy consumption of 1.2 kW h/m 3 . Farhadi et al. (2012) investigated the efficiency of using peroxi-electrocoagulation system for the treatment of pharmaceutical wastewater [94]. The removal efficiency of COD after EC alone was 34.2% using DC power supply, 1.7− 1.9 mA/cm 2 current density, 60 min electrolysis time, 4 iron electrodes, 2.5 cm electrodes spacing and initial pH value of 7. At the optimal condition, the energy consumption for EC was 65.06 kW h/kg COD. ...
Article
Electrocoagulation (EC) has attracted attention during the recent years due to its ease of use and high removal rate of organic and inorganic pollutants. It was found that using EC as a pretreatment process can decrease the overall energy consumption and improve the treated water quality. This literature review evaluates the efficiency of integrating EC process with other water treatment processes including membranes, chemical, electromagnetic and oxidation processes. The studied technologies were ultrafiltration (EC-UF), reverse osmosis (EC-RO), forward osmosis (EC-FO), membrane distillation (EC-MD), forward osmosis-membrane distillation (EC-FO-MD), membrane bioreactor (EC-MBR), electrodialysis (EC-ED), ozonation (EC-O3), ultraviolet (EC-UVC/VUV), peroxi-electrocoagulation (EC-H2O2), activated carbon adsorption (EC-AC), biofiltration (EC-BF) and electro-oxidation (EC-EO). The overall performance was evaluated using pollutants removal efficiency, energy consumption and operational cost. Then, the performance of pilot scale hybrid electrocoagulation processes and the current status of implementation was discussed. The future potential of electrocoagulation lies with proper hybridization of EC with other water treatment processes that would minimize the overall cost and enhance quality of the treated water.
... Subsequently, Eqs. (6) and (7), the coagulation steps may act as polishing steps to remove the remaining pollutants through physical adsorption after EF oxidation (Farhadi et al., 2012). During EC process with carbon steel electrodes, O • H radicals were not detected during the treatment of raw car wash wastewater treatment. ...
Article
Electrocoagulation (EC) is an acclaimed environmentally adequate approach to wastewater treatment. It is simple and economical by way of reducing the amount of chemical dosage, sludge generation and disposal, and the high costs involved in traditional chemical coagulation (CC). This paper discusses the mechanisms of pollutant removal by electro-generated hydroxide and oxyhydroxide flocs during EC process. The flocs’ generation and formation with Fe, Al and other metal electrodes, and the influence of operating conditions (pH, current density, electrolyte composition, etc.) on floc structure are reviewed. Further, revisions were provided on recent studies about new areas in electro-generated (oxy)hydroxide flocs such as layered double hydroxides (LDHs) and green rusts (GR), common characterization techniques, and factors promoting EC floc production. Results clearly indicate that during EC, the most proposed removal mechanisms of (oxy)hydroxide flocs towards oxyanions, cationic heavy metals, and organic pollutants are adsorption and coprecipitation, charge neutralization and surface complexation, and direct/indirect radical oxidation respectively. EC process alone which has low radical generation is less efficient when treating organic pollutants. Consequently, coupling and combination of AOP-EC generates suitable amounts of radicals and flocs for organic pollutant removal.
... Ameziane et al. [34] treating hospital wastewater by EC achieved a reduction efficiency of 79.2 % for COD, 93.7 % for suspended solids and 97.3 % for the total faecal coliforms. Farhadi et al. [35] studied the COD reduction in pharmaceutical wastewater adopting iron electrodes, obtaining 34.2 % of COD reduction with an electric energy consumption of 65.06 kW h/kgCOD. ...
Preprint
Tannery wastewater contains large amounts of pollutants that, if directly discharged into ecosystems, can generate an environmental hazard. The present investigation has focused the attention to the remediation of wastewater originated from tanned leather in Tunisia. The analysis revealed wastewater with a high level of chemical oxygen demand (COD) of 7376 mgO2/L. The performance in reduction of COD, via electrocoagulation (EC) or UV photolysis or, finally, operating electrocoagulation and photolysis in sequence was examined. The effect of voltage and reaction time on COD reduction, as well as the phytotoxicity were determined. Treated effluents were analysed by UV spectroscopy, extracting the organic components with solvents differing in polarity. A sequential EC and UV treatment of the tannery wastewater has been proven effective in the reduction of COD. These treatments combined afforded 94.1 % of COD reduction, whereas the single EC and UV treatments afforded respectively 85.7 and 55.9 %. The final COD value of 428.7 mg/L was found largely below the limit of 1000 mg/L for admission of wastewater in public sewerage network. Germination tests of Hordeum Vulgare seeds indicated reduced toxicity for the remediated water. Energy consumptions of 33.33 kWh/m3 and 314.28 kWh/m3 were determined for the EC process and for the same followed by UV treatment. Both those technologies are yet available and ready for scale-up.
... Ameziane et al. [34] treating hospital wastewater by EC achieved a reduction efficiency of 79.2 % for COD, 93.7 % for suspended solids and 97.3 % for the total faecal coliforms. Farhadi et al. [35] studied the COD reduction in pharmaceutical wastewater adopting iron electrodes, obtaining 34.2 % of COD reduction with an electric energy consumption of 65.06 kW h/kgCOD. ...
Article
Tannery wastewater contains large amounts of pollutants that, if directly discharged into ecosystems, can generate an environmental hazard. The present investigation has focused the attention to the remediation of wastewater originated from tanned leather in Tunisia. The analysis revealed wastewater with a high level of chemical oxygen demand (COD) of 7376 mg O2 /L. The performance in reduction of COD, via electrocoagulation (EC) or UV photolysis or, finally, operating electrocoagulation and photolysis in sequence was examined. The effect of voltage and reaction time on COD reduction, as well as the phytotoxicity were determined. Treated effluents were analysed by UV spectroscopy, extracting the organic components with solvents differing in polarity. A sequential EC and UV treatment of the tannery wastewater has been proven effective in the reduction of COD. These treatments combined afforded 94.1 % of COD reduction, whereas the single EC and UV treatments afforded respectively 85.7 and 55.9 %. The final COD value of 428.7 mg/L was found largely below the limit of 1000 mg/L for admission of wastewater in public sewerage network. Germination tests of Hordeum Vulgare seeds indicated reduced toxicity for the remediated water. Energy consumptions of 33.33 kW h/m 3 and 314.28 kW h/ m 3 were determined for the EC process and for the same followed by UV treatment. Both those technologies are yet available and ready for scale-up.
... The techniques for removing pharmaceutical pollutants from water bodies can be summarized into four types: membrane separation, 17,18 chemical decomposition, 19,20 adsorption, 21,22 and photocatalysis. 23,24 However, these techniques always have shortcomings such as low efficiency, environmental unfriendliness and high cost in practical operation. ...
Article
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Anesthetic drug wastage has increasingly become the main resource of operating room sewage, which poses a great risk to the safety of humans and other organisms. Propofol is the most widely used anesthetic drug in the world, and also occupies the largest proportion of the total anesthetic wastage in the operating room. In this work, a 2D Cu2O anchored carbon catalyst (Cu2O@NC) was prepared by the assembly-pyrolysis process and successfully applied to peroxymonosulfate (PMS) activation. We took propofol as a typical example and investigated the removal activity through heterostructure-enhanced advanced oxidation processes (AOPs). Through the degradation process, propofol can be removed from 20 ppm to ultralow levels within 5 min using the PMS/Cu2O@NC system. The degradation pathway of propofol was deduced through quantum chemical calculation and LC/GC-MS results. The final products were verified as CO2 and H2O. Moreover, sulfate radicals (SO4˙-) proved to be the dominant reactive oxidation species by radical scavenger experiments and ESR results. In addition, it has great universality for various pharmaceuticals such as tetracycline (TC), amoxicillin (AMX), cephalexin (CPX), and norfloxacin (NFX). Our work provided the possibility to treat operation room sewage in a rapid, high-efficiency, and feasible way.
... The main function of stirring speed is to transfer efficiently the coagulant matter which is formed by the solution of electrodes to reactor. If coagulant matter does not disperse in the reactor efficiently, content of the reactor cannot be homogenous and regional differences can be se cell and yet was not strong enough to break up the flocs formed during the processes [12] . It can be seen the highest removal efficiency species generated from the 'sacrificial anode' for a ...
Article
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The decolorization of Rhodamine B (RB) dye from aqueous solution� was investigated using electrocoagulation (EC) in a batch electrochemical cell. The respective effects of operational parameters such as initial pH, initial dye concentration, current density, and electrolysis time were analyzed by comparing the removal efficiency. The complete colour removal has been recorded under the optimized conditions of natural pH of 7.0, current density of 15 mA/cm2, treatment time of 60 min and dye concentration of 50mgL-1. The untreated and treated sample was characterized by UV–vis spectroscopy to confirm the process performance. The SEM study of sludge confirms the amorphous nature of the Fe products. EDAX spectra provide information about the elemental composition such as Fe, Na, O, and Cl are present in the Fe treated sludge. The sludge formed during electro coagulation was characterized by SEM/EDAX analysis.
... Electrocoagulation (EC) is one of the widely-applied electrochemical techniques to treat wastewater and an advanced alternative to chemical coagulation [3]. As an independent or hybrid system, EC has been applied industrially to treat wastewater from textile dyes, pharmaceutical wastewater, oil tanning effluent, heavy metals, and other industrial wastewaters [4][5][6][7][8][9]. Electrocoagulation mainly consists of an electrolyte, usually the wastewater, and two sacrificial electrodes, anode and cathode. ...
Article
In this study, electrocoagulation was evaluated for landfill leachate as a complex wastewater. Effects of all significant parameters including inter-electrode gap, current density, electrode material, time, pH, electrode numbers, salinity, and concentration were investigated. This study reports the changing patterns for chemical xxygen demand (COD) removal, temperature, voltage, and pH during EC for both Fe and Al electrodes under different conditions. According to the results, the best COD removals were achieved at shortest inter-electrode distance (0.5 cm), highest current density (1000 A m−2), highest number of electrodes (6 plates), longest time (60 min), and within acidic pH. Furthermore, for different NaCl concentrations (0–16 g l−1), both falling and rising patterns were observed. This study also provides separate results for the effect of operational parameters on pH, voltage, temperature, and energy consumption during EC. With higher inter-electrode distances, voltage and temperature rose to larger values, whereas pH fell. Besides, increases in initial pH caused rises in all voltage, temperature and pH parameters during EC. Experiments also displayed that higher values of voltage, temperature, and pH occurred at larger current densities. Additionally, with time, pH increased to more basic measures, and voltage similarly increased. Results also reported that although addition of NaCl into medium could drop the voltage and temperature, it formed both falling and rising patterns for pH at different NaCl concentrations. Plus, according to the results, voltage, temperature, and pH all experienced rising patterns in accordance with the increase in the number of electrodes. Finally, a comparative study of energy consumption was performed to analyse the operation parametric effect.
... When comparing the results with other studies, it is found that they are similar or superior, in some cases, to those reported by: Elazzouzi, et al. [29], for urban wastewater electrocoagulation/flocculation treatment (COD: 85%, BOD: 84%; TSS: 94%; and PO4: 99%); Farhadi, et al. [30], for COD removal from pharmaceutical wastewater by electrocoagulation processes (< 35%); Wang, et al. [31], for COD removal from domestic wastewater by electrocoagulation (62%); Hutnan, et al. [32], for COD removal from urban wastewater by electrocoagulation (COD: 50-80%); Chen, et al. [33], for COD removal from wastewater (restaurants) by electrocoagulation (COD: 95-99%); Pouet and Grasmic, [34] for COD removal from urban wastewater by electrocoagulation (COD: 70-80%); Fajardo, et al. [35], for synthetic wastewater treatment by electrocoagulation (phenols: 84.2%; COD: 40.3%) and for olive oil effluent wastewater treatment (phenols: 72.3%; COD: 20.9%); Bazrafshan, et al. [36], for phenol removal from aqueous solutions by the electrocoagulation process using iron (94.7%) and aluminum (98.0%) electrodes; Irdemez, et al. [37], for phosphates removal from wastewater by electrocoagulation using aluminum electrodes (99-100%); Kuokkanen, et al. [38], for phosphates removal from synthetic wastewater by electrocoagulation (96%); and Franco, et al. [39], for phosphates removal from wastewater by electrocoagulation (99%). ...
Article
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The technical feasibility of the continuous flow electrocoagulation process for hospital wastewater treatment was evaluated. The wastewater physicochemical characterization was performed according to the chemical oxygen demand (COD), biochemical oxygen demand (BOD), total suspended solids (TSS), naproxen, phenol and phosphates parameters. An experimental Box-Behnken design and statistical response surface methodology (RSM) were used to evaluate the simple and combined effects of the independent parameters (pH, potential, retention time), and to optimize electrocoagulation process conditions, considering the COD response variable. The removal percentage was: COD (75.5%), BOD (59.2%) phenols (80.7%), phosphates (85.3%), TSS (75.6%) and naproxen (55.7%), under optimal electrocoagulation conditions at pH (7.92), potential (40 V) and retention time (15 min). The electrocoagulation process proved to be an efficient and technically viable alternative for hospital wastewater treatment.
... Overall, the addition of H 2 O 2 to the EC process resulted in the complete decolourization of distillery effluents along with a total COD reduction of 86% and energy consumption of 1.1 kW h/m 3 . Farhadi et al., 2012 evaluated the performance of peroxi-EC process for the removal of high concentrations of COD from pharmaceutical effluent [103]. In the EC process, 4 Fe electrodes were used having an inter-electrode distance of 2.5 cm between them and is connected to a DC power source. ...
Article
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Electrocoagulation (EC) is an established wastewater treatment method that has been widely explored for a broad range of wastewater pollutants due to its ease of operation, versatility, eco-friendly nature and low footprint. EC as a pretreatment process can significantly reduce the total energy usage, while also improving the quality of treated water. This review paper provides an in-depth assessment of the various operational parameters and electrode materials used during the electrocoagulation treatment of wastewater. The recent advancements in EC reactor designs and optimization studies have been reviewed. The effectiveness of combining the EC process with other water treatment techniques viz. membranes, oxidation, chemical and adsorption processes have also been validated in this review paper. Different combinations of EC process with microfiltration (EC-MF), ultrafiltration (EC-UF), nanofiltration (EC-NF), reverse osmosis (EC-RO), ozonation (EC-O3), peroxi-electrocoagulation (EC-H2O2) and electro-oxidation (EC-EO), have been elaborately discussed and summarized. The results are critically analyzed, and modifications have been suggested to improve the performance efficiency. Moreover, case studies regarding the application of the EC process from three different wastewater sources have been demonstrated. The economic aspects of the EC process and recommendation for its betterment is also made. Taken together, this review paper effectively illustrates the progress and current achievements in both standalone and hybrid EC process towards wastewater pollutant treatment, which can present new insights on improving the wastewater treatment scenario with promising environmental applications. The critical analysis and suggestions provided in this review paper will greatly enhance the scientific knowledge of the readers.
... However, based on the literature, there are many methods applied to remove this type of target pollutants from water. Part of them, traditional methods, such as coagulation, filtration, adsorption, however, results showed that these conventional techniques are insufficient, unable to reach degradation of organic substances and present several limitations for wastewater treatment [15][16][17][18][19][20][21]. ...
Article
Gamma irradiation degradation of the extensively used muscle relaxant in the world methocarbamol (MET) was studied. MET aqueous solutions were irradiated by gamma rays emitted by a Cobalt 60 source at doses of 1-4 kGy.Our findings demonstrated that gamma irradiation degraded more than 98.5% of MET. Absorption spectra analysis revealed that when increased irradiation dose the absorption bands declined with complete disappearance at 4 kGy dose. Additionally, the most radiolytic degradation rate was recorded at neutral pH, marked by Total Organic Carbon (TOC) removal rate of 98% reflecting the total mineralization of MET at 4 kGy. In-depth spectrophotometric analyses advocated a pseudo-first-order type of MET degradation kinetics. The obtained apparent rate constant value was kapp, MET = (0.02167 ± 0.0006) min-1. Gas chromatography-mass spectrometry (GC-MS) allowed the detection of 3-(o-Methoxyphenoxy)-1,2 propanediol,2-Methoxyphenol, 1,2,3 propanetriol, 1,2-dihydroxybenzene and 1,2,4 benzentriol identified as by-products generated during radiolytic degradation. Finally, an outline of the degradation mechanism was suggested according to the obtained by-products.
... Electrocoagulation (EC) is a process in which metal-ion coagulants are directly added to the feed water by in situ electrochemical dissolution of an anode. EC is a promising approach that has been widely used as pretreatment in the industrial wastewater (Farhadi et al. 2012;Lianos et al. 2014;Shenvi et al. 2015). It has many potential advantages such as (i) portability, (ii) reduced use of chemicals, (iii) decreased energy consumption and increased treatment capacity, and (iv) suitability for use in predesigned packaged plants (Moussa et al. 2017). ...
Article
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Low pressure reverse osmosis (LPRO) has been increasingly used in advanced treatment of pulp and paper wastewater (PPWW) for the purpose of water reuse. However, membrane fouling is a major problem encountered by full-scale RO systems due to the organic and inorganic contents of the feedwater. Electrocoagulation (EC) as an effective treatment for foulants removal can be applied in pre-filtration. Therefore, the LPRO membrane fouling mechanism and the membrane fouling control performance by EC treatment were investigated in this study. EC pretreatment could reduce the membrane fouling and improve the membrane flux by 31%, by effectively removing and/or decomposing the organic pollutants in PPWW. Fluorescent spectrometry analyses of the feedwater and the permeate revealed that humic acid-like and fulvic acid-like organics in PPWW were the major foulants for the LPRO membranes. Fourier transformation infrared spectrometry results confirmed that the organic foulants contained benzoic rings and carboxylic groups, which were typical for organic substances. EC effectively removed organic pollutants containing functional groups such as carboxylic acid COH out-of-plane bending, olefin (trans), and NH3⁺ symmetrical angle-changing. Moreover, the extended Derjaguin-Landau-Verwey-Overbeek model suggested that the membrane filtered 30-min EC-treated PPWW had the strong repulsion force to foulants due to the higher cohesion energy (12.1 mJ/m²) and the lower critical load, which theoretically explained the reason of EC pretreatment on membrane fouling control.
... If the coagulant matter does not disperse with the reactor efficiently, the reactor content cannot be homogenous, leading to regional differences. The chosen stirrer speed of 250 rpm was found suitable to mix the electrolyte cell well and strong enough to break up flocs formed during the processes [17]. The highest removal efficiency of 94.42% was reached at 250 rpm of stirrer speed and 90 min of treatment time (Fig. 4). ...
Article
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The electrochemical oxidation of reactive red 195 from aqueous solution was carried out using titanium electrode in an electrochemical cell reactor. The effect of different operating parameters such as dye concentration, current density, electrolyte concentration, pH and stirring speed were investigated. The UV-visible spectroscopy confirmed the removal and degradation of reactive red 195. Three different supporting electrolytes such as NaCl, NaNO3 and Na2SO4 were used for electrolysis and NaCl were found to be effective for the removal of reactive red 195 dye from its aqueous solution. The maximum percentage of colour removal was 94%, under the optimum operating conditions with electrolyte (NaCl) concentration 0.075 M, current density 25 mA/cm2, pH 5 and stirring speed of 250 rpm. This method was found to be relatively more effective to the conventional treatment techniques.
Article
In the current scenario treatment of industrial waste water is big challenge especially waste water that contain high organic load. Hydrogen peroxide assisted electrocoagulation (EC) process provides better result to treat highly polluted wastewater as compared to EC alone. However, hydrogen peroxide is well known as a strong oxidant, which cast a potential threat to human health. To overcome this problem hydrogen peroxide has been used here for treatment of wastewater in small quantity, and that consume during the process. Therefore the harmful effect of hydrogen peroxide in human and aquatic life could be minimized. This work is an attempt to treat biodigester effluent (BDE) using H 2 O 2 assisted EC processes with respect to chemical oxygen demand (COD) and color reductions. To perform this experiment both iron and aluminum electrodes are used as an electrode material in the presence of H 2 O 2 . In case of iron electrode the maximum COD and color reduction efficiency of 98.3 and 83.6% was achieved at the cost of 1.5 Wh/dm ³ energy consumption while maximum COD and color removal efficiency of 96.8 and 77.1% with 1.7 Wh/dm ³ of energy consumption was observed in the aluminum electrode based EC process. A part from this conventional biological process (i.e., activated sludge treatment, ponds, and lagoon etc.) and physiochemical treatment process (i.e., coagulation, adsorption) provided treatment efficiency of 40–80% hence hydrogen peroxide assisted EC process should a better choice to treat distillery effluent. Furthermore, hybrid EC process was also performed with iron used as anode and aluminum as cathode in the presence of H 2 O 2 . Iron electrode based peroxi-EC process provided better result at optimum operating conditions; current density of 114 A/m ² , initial COD concentration of 12,000 mg/dm ³ , initial pH of 7.3, H 2 O 2 concentration of 120 mg/dm ³ , stirring speed of 120 rpm and electrolysis time of 90 min. The cost estimated for operation is 1.56 US $/m ³ . Finally, sludge analysis and cost optimization are also incorporated in this article.
Article
Electrocoagulation is a promising method for removing pollutants from surface water and industrial wastewater. The coagulation efficiency is dependent on pH but it is not fully understood how electrocoagulation affects pH of the treated water. Three series of experiments have been conducted to study how 1) chloride and sulphate anions, 2) negatively charged organic macromolecules and 3) carbonate influence pH during electrocoagulation. It is found that dissolved carbonate has a significant influence on the pH change as CO2 is stripped off during electrocoagulation due to formation of H2 microbubbles at the cathode. The pH increased by ~1 pH unit, which may significantly affect coagulation efficiency of iron. The pH increase depended strongly on the initial pH and the concentration of carbonate in the water. A secondary contribution to pH change was found to be ion exchange by sulfate and chloride ions into Fe(OH)3 flocs, whereby OH‐ was released into solution but only minor pH change was observed, not enough to affect the coagulation. The presence of charged organic macromolecules did not have any significant effect on pH. This article is protected by copyright. All rights reserved.
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The presence of trace levels of pharmaceutically active compounds (PhACs) in the aquatic environment threatens human health and the environment. Metronidazole (MNZ) is a soluble PhAC with low biodegradability, a possible human mutant and carcinogen. This study aimed at synthesis, characterization, and employment of porous amine-modified green-graphene (AMGG) for MNZ removal from aqueous solutions. Response-surface methodology (RSM) based on Box-Benken design (BBD) was used to assess the MNZ adsorption efficiency of AMGG as a function of pH (4-12), contact time (5–60 min), AMGG dose (0.1-1 g/L) and MNZ concentration (10–100 mg/L). From the model optimization, the highest MNZ removal was predicted at a pH of 5.9, a contact time of 27 min, an AMGG dose of 0.86 g /L, and a MNZ concentration of 100 mg /L. The experimental data were in agreement with the pseudo-second order kinetic model and the Langmuir adsorption equation, which implied the adsorption occurred in monolayer and the adsorbed molecules uniformly distributed on the adsorbent surface. The maximum adsorption capacity of AMGG for MNZ was 416.7 mg/g. The MNZ concentration at equilibrium increased about 4.8 mg/L when the solution temperature increased 20 ºC from 303 to 323 K, indicative of exothermic process. AMGG showed a removal efficiency of 74% when it was employed for real wastewater treatment. Moreover, AMGG showed an efficiency decrease from 84% to 57%, after five consecutive saturation-regeneration cycles.
Article
Water recycling is of increasing concern due to the shortage of natural resources, calling for advanced methods to remove contaminants. Indeed, the transfer of contaminants to living organisms may lead to bioaccumulation and diseases. In particular, the overuse of antibiotics for human and animal health has led to antibiotic pollution in waters, sludges and crop soils, and, in turn, to the unintended development of multi-resistant bacteria, named antibiotic resistance. Here we review antibiotic properties, antibiotic occurrence in wastewater, and antibiotic removal. Remediation techniques include electrocoagulation, photocatalysis, Fenton process, sonocatalysis, ozonation, membrane filtration, adsorption and ionizing irradiation. Nanofilters and reverse osmosis showed the highest removal of antibiotics in a bioreactor, averaging at 95%. Recently developed methods such as photocatalysis, sonocatalysis and ozone oxidation show a removal of about 98%.
Article
The significant increase in the turnip sector has brought a wastewater problem that needs to be managed. In this study, turnip juice wastewater treatment was studied using the electrocoagulation/electroflotation and electrooxidation processes. Independent process parameters such as electrode type (aluminum–aluminum, iron–iron, boron-doped diamond–platinum and graphite–platinum), current density (25–100 A/m2) and retention time (15–180 min) were investigated for the optimization of treatment conditions. Removal efficiencies of chemical oxygen demand and total phenol were studied. It was determined that the optimum removal efficiencies in both electrocoagulation/electroflotation and electrooxidation processes were the same under the conditions of 100 A/m2 current density, pH 5.4, and 45 min reaction time. Here, 100% removal efficiencies were achieved for both chemical oxygen demand and total phenol. The operating cost of the electrocoagulation/electroflotation process was calculated as 1.58 $/m3, while it was determined as 0.61 $/m3 for electrooxidation for the optimum removal parameters. It is seen in laboratory scale test results that electrocoagulation/electroflotation and electrooxidation processes are applicable/feasible for the treatment of turnip juice wastewater.
Article
This study investigated the physicochemical properties of bovine manure biochar (BC) obtained at different temperature of 500 °C (BC-500) and 700 °C (BC-700). The effects of the contact time, temperature, pH, background electrolyte, and regenerated adsorbent on the adsorption of tetracycline (TC) by BC-500 and BC-700 were determined. The TC removal rates were 95.31% by BC-500 after 12 h and 99.70% by BC-700 after 4 h. The maximum adsorption capacities of BC-500 and BC-700 were 5.38 mg/g and 5.82 mg/g, respectively. The adsorption of TC by BC-500 and BC-700 was characterized better by pseudo-second order kinetics. The adsorption kinetics of BC-500 and BC-700 were fitted well by the pseudo-second order kinetic model. Regeneration experiments showed that BC-500 and BC-700 still delivered satisfactory removal efficiencies even after three cycles, 52.95% and 77.20%, respectively. The main mechanisms responsible for the adsorption of TC by BC were determined as hydrophobic interactions and π-π electron donor acceptor interactions. This new type of inexpensive and readily available adsorbent may provide an effective solution for the removal of TC from wastewater in the future.
Article
The present work aims to study chemical oxygen demand (COD), oil‐grease, and color removal from vegetable oil wastewater by combined electrocoagulation and activated sludge processes. For this purpose, the sample was pre‐treated using electrocoagulation by various optimization parameters such as electrode type (Al‐Al, Fe‐Fe), current density (100‐400 A/m2), pH (2‐8), and electrolysis time (15‐180 min). The results showed that 89.3% of COD, 100% of oil‐grease, and 66.2% of color were removed by electrocoagulation under the conditions of 300 A/m2 current density, pH 2, and 180 min reaction time with Al‐Al electrode pairs. Then, the effluent of electrocoagulation was treated by an activated sludge process. The results depicted that the activated sludge process was also effective for vegetable oil wastewater treatment and it enhanced 98.9% COD and 79.2% color removal efficiency. The effluent of the combined process was very clear and its quality exceeded the direct discharge standard of the water pollution control regulation. The laboratory‐scale test results indicate that the combined electrocoagulation and activated sludge process is feasible for the treatment of vegetable oil wastewater.
Article
Electrocoagulation (EC) and electrocoagulation-flotation (ECF) are of widespread interest owing to their effectiveness for the simultaneous abatement of a broad range of pollutants in drinking and waste waters, but their capability can vary significantly depending on the operating conditions. The effect of operating conditions on the performance of EC has been the subject of much debate over the last few decades. This review aims to focus on the application of EC/ECF processes for pollutants removal under different operating conditions, emphasizing the principal issues that compose the foundation of EC/ECF. It has been found that the current density (typically 1–20 mA/cm²), type of electrode (Al or Fe), and electrolysis time are the key process parameters that influence performance. Although some key mechanisms of pollutant abatement in EC/ECF processes have been identified, recent studies have begun to reveal how the underlying removal mechanisms using the EC/ECF processes depend on the nature of pollutant. Key mechanisms of pollutant abatement include charge neutralization, reduction–oxidation, and precipitation/co-precipitation. The development of improved or innovative cell designs, as well as systematic modeling of EC reactors, are needed. Future research focused on hybrid technologies with cost-effective energy supply may lead to innovative treatment options for wastewater treatment.
Article
Increasing discharge of saline wastewater (SWW) from different industries and environmental risks associated with it has compelled researchers to search for efficient treatment methods and safe disposal techniques. Unfortunately, several industries such as agro-food, oil & gas, tannery, and pulp & paper require brine solution units to obtain a finished product that further elevates the salinity of discharged wastewater to a magnitude of 1-3% by weight of NaCl. Among the conventional treatment procedures, electrochemical technologies proved to be more efficient, robust and cost-effective. Electrocoagulation (EC), an electrochemical based technology that produces in situ coagulant which ultimately assist in pollutant removal. It is even more suitable for the treatment of saline water as salinity increases conductivity which further enhances the EC process efficiency. However, the elevated anodic dissolution may increase the cost which can be reduced by using scrap metals as sacrificial electrodes out of iron and aluminum. The mechanism of salt removal from SWW using EC is similar to other pollutant removal mechanisms as salt species being coagulated by the metal hydroxides and are further removed as sludge. However, optimization of process parameters in EC is essential to maintain a balance between anodic passivation and higher metal dissolution so as to make the process efficient. This review paper highlights the theory of the EC technology, process parameters, potential application and recent developments of EC for the treatment of various types of SWW as well as economical assessment associated with this technology. Most of the recent research concerning EC for SWW treatment has been concentrated on the pollutant-specific evaluation without paying special attention to the process optimization, process modelling and commercial usage. This review further outlines the challenges with the recommendations for encouraging research options that can potentially enhance the EC performance, lower the operational costs and expand its range of applications for SWW treatment.
Article
The presence of emerging pollutants in the environment can pose potential risks to the natural ecosystem. Thus, the efficacious removal of emerging pollutants, like pharmaceuticals from wastewater have recently been a major area of concern for the researchers; since, these biorefractory compounds can bio-accumulate in living beings and can also transform into other toxic compounds in the natural environment. Pharmaceuticals are not efficiently removed through conventional wastewater treatment technologies. Thus, the development of reliable and efficient treatment technologies for the removal of pharmaceuticals is imperative. One such plausible treatment technology is electrocoagulation (EC), which is an electrochemical process that works on the process of in-situ production of coagulants within the EC setup via metal electrodes due to the application of electric current. Therefore, in this review the application of EC for the removal of pharmaceuticals, critical parameters that influence the treatment efficiency, comparison of EC with chemical coagulation and the economics pertaining to EC have been discussed. The goal of this state-of-the-art review is to provide updated information on the application of EC for the removal of pharmaceuticals, which lacks in the previous review articles. Moreover, this would assist the readers to take this technology forward in terms of commercialization as well as removal of pharmaceuticals from contaminated water and thus to produce treated water safe for different reuse purpose.
Chapter
Many pharmaceutical companies utilize confidentiality composition as a means to escape the norms imposed by the pollution regulation control. Derivatives of pharmaceutical compounds (hormones, volatile organic compounds, antibiotics, and surfactants) and their metabolites are toxic (ecosystem of aquatic, terrestrial, and human health), and antibiotic-resistant microbial species are wastewater sources from houses, pharmaceutical industry, and hospitals. The wastewater comprises large quantity of salt, organic matter, microbial toxicity creating COD and BOD, and ever-increasing innovations in the field of medicine also increases the usage of pharmaceutical drugs, thereby increasing the rate of pollution. Pollution begins from the production and processing of pharmaceutical products until the cycle of consumption. This chapter explicates pharmaceutical contamination and pollution created by personal care products and addresses the means of elimination by biological and chemical methods like adsorption / bioadsorption, activated carbon adsorption, sedimentation, coagulation, advanced oxidation processes, photooxidation, ozonation, biological treatment, and electrochemical processes. Eco-friendly approaches are derived from the biological treatment by microbial process (composting, vermicomposting, aerobic and anaerobic techniques), and they do not produce secondary waste and also convert the toxic to non-toxic form. This has also demonstrated the benefits and demerits of the removal measures. This chapter summarizes the important overviews of key publications on pharmaceutical products.
Article
The wastewater of an opium pharmaceutical industry was successfully treated using a combined process of electrocoagulation/flotation (ECF), peroxone (H2O2/O3) and adsorption filter of granular activated carbon (GAC) in a three-step operation (ECF → H2O2/O3 → GAC), in a lab and semi-industrial scales. The effect of the operating parameters such as initial pH, current density, residence time, injection dose of H2O2, the ratio of H2O2/O3 and time of adsorption process was optimized in both scales. On the lab-scale, the removal efficiency of COD, Color, TDS, TSS, electrical power consumption, electrode consumption, and operating costs have been studied. In the ECF process, the maximum removal efficiencies of COD, color, TDS and TSS were 64%, 60%, 61% and 50%, respectively. The optimum pH, ozonation time, hydrogen peroxide concentration and the ratio of H2O2/O3 in the peroxone process are 8, 45 min, 900 mg/l, 0.3 H2O2/O3, respectively. After ECF and peroxone processes, the maximum removal efficiencies of COD and color increased up to 84% and 62% and after the adsorption process, the maximum removal efficiencies of COD, Color, TDS, and TSS increased up to 99.2%, 99.0, 99.0 and 99.1%, respectively. The performance of each reactor in the semi-industrial scale was also evaluated. After the treatment operation in the ECF → H2O2/O3 → GAC semi-industrial pilot reactor, the COD removal efficiency, Color, TDS and TSS of opium wastewater reached 96%, 99%, 99% and 99%, respectively. The excellent performance, as well as the low operating cost, confirmed that this integrated system is highly applicable for the advanced treatment of opium pharmaceutical industry wastewater.
Chapter
The rapid fiscal growth of any nation has caused an increase in population, urbanization, and industrialization, thus leading to high generation of Municipal Solid Waste (MSW). Due to its complex properties and composition, MSW often produces a by‐product known as leachate, high‐strength wastewater which may become a major contribution to water pollution if not properly tended. Optimizing the treatment of landfill leachate to minimize its adverse impacts on the natural ecosystem is an urgent concern. Over the last decades, sophisticated technological innovations in landfill leachate treatment have gained increasing attention. Recently, advanced oxidation processes in leachate treatment such as the electrocoagulation (EC) method have been receiving much focus due to their outstanding ability in eliminating pollutants, economic viability, and green approaches. Therefore, this chapter presents an overview of the basic characteristics of landfill leachate and the promising electrocoagulation process in decontaminating leachate pollution. Reviews on the fundamentals and mechanism of an electrocoagulation process, including its history and theory as well as its benefits and drawbacks, are updated with a focus on landfill leachate treatment. The influences of the treatment process variables toward its performance efficiency, including the need for electrolyte, are discussed and critically analysed. A case study on the application of the EC method in treating local landfill leachate is reviewed.
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Exponential growth in the industrial sector causes the accumulation of toxic wastewater in the ecosystem. The unsafe disposal of such wastewater not only adversely affects the freshwater resources but also pose negative impact on the environment and human health due to the presence of heavy metals, organic/inorganic pollutants, and high amount of nitrogen, phosphorus, and sulfur in it. It demands for the effective wastewater treatment that depends on the effluent quality, industrial process, chemical/energy requirement, economic viability, operational flexibitily, and residual utilization. However, conventional treatment methods are unable to meet all the requriements which demands for the eco-friendly and economical alternatives. Currently, paradigm shift from wastewater treatment and dispoal of, to its utilization in circular biorefinery context is underway. In this context, microalgae-based industrial wastewater is vital option due its pollutant accumulation ability, environmental sustainablity, biorefinery potential, and zero-waste process chain development. This review highlights the characteristics of different industrial effluents and overviews the axenic and binary algal-treatment systems. Economical and technological barriers are the major hindrance in the implementation of algal-based treatment methods; for which biomass valorization has been briefly discussed. This review highlights the need of developing closed-loop integrated processes for wastewater treatment and reuse in sustainable manner. Further research in the development of such schemes specially at large-scale level must be the focus of future studies.
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The electrochem. behavior of PbO2 and synthetic B-doped diamond thin film electrodes (BDDs) was studied in acid media contg. 4-chlorophenol (4-CP) by bulk electrolysis under different exptl. conditions. To quantify the electrochem. activity of a given electrode, for the electrochem. oxidn. of org. compds. (4-CP), the current efficiency of the anodic oxidn. was normalized taking into consideration mass-transport limitations. The normalized current efficiency (j) was defined as the ratio between the current efficiency of the investigated anode to the current efficiency of an ideal anode which has a very fast oxidn. rate, resulting in a complete combustion of orgs. to CO2. The results showed that even if the complete combustion of 4-CP was achieved at both PbO2 and BDD anodes, the latter give higher j. The difference in reactivity of the electrogenerated hydroxyl radicals on the anode surface, is proposed to explain the high j values obtained using B-doped diamond anodes. [on SciFinder (R)]
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BACKGROUND: The present study describes an electrocoagulation process for treating laundry waste-water using aluminum plates. The effect of various parameters such pH, voltage, hydraulic retention time (HRT), and number of aluminum plates between the anode and cathode on efficiency of treatment are investigated. RESULTS: Experimental results showed that by increasing HRT, treatment efficiency increases but beyond 45 min changes are negligible. Among the results for chemical oxygen demand (COD), phosphorus, detergent, colour and turbidity, the lowest decrease was found for phosphorus. The larger the HRT, the greater the electrical current needed to achieve constant voltage and temperature in the system. The pH of the influent is a very significant variable which affects the treatment of laundry waste-water considerably, the optimal range being 6.0–8.0. In addition, it was found that the pH increases from 8.3 to more than 10 over the first hour of treatment after which the pH remains relatively constant. Finally, kinetic analysis indicates that the adsorption system obeys a second-order kinetic model. CONCLUSION: The aluminum hydroxide generated in the cell decreases the concentration of pollutants in laundry waste-water to a permissible level. It is concluded that, compared with other treatment processes, electrocoagulation is more effective in treating laundry waste-water under appropriate conditions. Copyright
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Electrocoagulation (EC) process using aluminum electrodes is proposed for removing fluoride from treated industrial wastewater originated from steel industry. Effects of different operating conditions such as temperature, pH, voltage, hydraulic retention time (HRT) and number of aluminum plates between anode and cathode plates on removal efficiency are investigated. Experimental results showed that by increasing HRT, removal efficiency increases but after 5 min changes are negligible. Therefore, the total HRT required is only 5 min. The more HRT, the more electrical current is needed in order to achieve to constant voltage and temperature in system. In addition, it is found that pH value decreases from 6.91 to 4.6 during first 10 min but it increases up to 9.5 during 50 min. After treatment, the fluoride concentration was reduced from initial 4.0-6.0 mg/L to lower than 0.5 mg/L. The pH of the influent is found as a very important variable which affects fluoride removal significantly. The optimal range for the influent is 6.0-7.0 at which not only effective defluoridation can be achieved, but also no pH readjustment is needed after treatment. Moreover, increasing number of aluminum plates between anode and cathode plates in bipolar system does not significantly affect fluoride removal. Finally, the kinetic analysis is done for the system which indicates that the adsorption system obeys the second-order kinetic model.
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Over the past few years, pharmaceuticals are considered as an emerging environmental problem due to their continuous input and persistence to the aquatic ecosystem even at low concentrations. Advanced oxidation processes (AOPs) are technologies based on the intermediacy of hydroxyl and other radicals to oxidize recalcitrant, toxic and non-biodegradable compounds to various by-products and eventually to inert end-products. The environmental applications of AOPs are numerous, including water and wastewater treatment (i.e. removal of organic and inorganic pollutants and pathogens), air pollution abatement and soil remediation. AOPs are applied for the abatement of pollution caused by the presence of residual pharmaceuticals in waters for the last decade. In this light, this paper reviews and assesses the effectiveness of various AOPs for pharmaceutical removal from aqueous systems.
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The objective of this work was to investigate the oxidation of p-hydroxybenzoic acid by the Fenton's reagent. Batch experiments were carried out to investigate the influence of the most important process variables: hydrogen peroxide and ferrous salt concentrations, pH, and temperature. The optimal results obtained indicate that p-hydroxybenzoic acid can be effectively degraded using Fenton's oxidation within 10-min reaction time by using a molar ratio H2O2: p-hydroxybenzoic acid of 4:1 and H2O2:Fe2+ of 15:1, at 30 degrees C and pH=3.0. The behavior of ORP and pH along the reaction time for different values of R (molar ratio H2O2: p-hydroxybenzoic acid) was also discussed. A pseudo-first order model was applied to describe the oxidation kinetics of p-hydroxybenzoic acid by Fenton's reagent.
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Degradation of MTBE, a common fuel oxygenate, was investigated using anodic Fenton treatment (AFT) and by comparison with classic Fenton treatment (CFT). The AFT system provided an ideal pH environment (2.5-3.5) for the Fenton reaction and utilized gradual delivery of ferrous iron and hydrogen peroxide, which was more efficient than batch CFT to degrade MTBE and its breakdown products. The optimized ratio of ferrous iron to hydrogen peroxide for AFT was determined to be 1:5 (in mmol). Depending on the initial concentration, MTBE was completely degraded by the optimized AFT in 4-8 min. The breakdown products found during the treatment of MTBE were acetone, t-butyl formate, t-butanol, methyl acetate, acetic acid, and formic acid, which were all completely degraded by the optimized AFT in 32 min. Based on the experimental results and other work reported in the literature, degradation mechanisms of MTBE and its breakdown products in AFT and CFT were proposed. Generally, reactions are initiated by H-abstraction by *OH, generating carbon-centered radicals which undergo various reactions including alpha/beta-scission within the radical, combination with oxygen, oxidation by ferric ion, and reduction by ferrous ion before generating the final oxidation products. Radical combination with oxygen (and the reactions thereafter) and radical oxidation by ferric ion are believed to be the most important pathways in the overall fate of the generated radicals, while radical reduction by ferrous ion is the least important. By elucidating the reaction kinetics and mechanisms of MTBE degradation in the anodic Fenton system, this study offers a potential remediation technique for treating MTBE-contaminated wastewater.
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The degradation of azo dye C.I. Acid Red 14 (AR14) was investigated using cast iron in the absence and presence of low frequency ultrasound (59 kHz). The effects of pH, amount of cast iron ([Fe](0)) and initial concentration of AR14 ([dye](0)) on the degradation of AR14 by cast iron combined with low frequency ultrasound had been assessed. The degradation followed the first-order kinetics model. The first-order rate constant of AR14 degradation by cast iron was 7.50 x 10(-2) min(-1) while that by US-cast iron was 2.58 x 10(-1) min(-1). A 3.4-fold increase in the reaction rate was observed in the presence of ultrasound compared with that of absence of ultrasound. This kinetic effect is quantitatively accounted for a simple kinetic model based on the reaction of Fe(II) from cast iron in aqueous solution with sonochemically produced H(2)O(2) (Fenton's reaction). This latter effect illustrates a simple way of achieving a substantial improvement in the efficiency of sonochemical degradation reactions. It was found that for azo dye AR14, the rate of color decay was the first order with respect to the visible absorption of the dye. The destruction of the naphthalene rings in azo dyes was slower than that of color. A significant mineralization of AR14 was observed.
Article
A combination of the classical Fenton reaction (Fe(II)+H2O2) with UV light, the photoassisted Fenton reaction, has been investigated for the treatment of landfill leachate. The investigation has been carried out with an experimental set-up to establish the optimal treatment conditions. The degradation rate of organic pollutants is strongly promoted by the photoassisted Fenton reaction. The degradation rate depends on the amount of H2O2 and Fe(II) added, pH value, and radiation intensity. At a specific energy input of 80 kW m−3 the oxidation rate was increased to six times the rate without radiation (0 kW m−3). At the higher radiation intensity of 160 kW m−3 the degradation rate was about two times faster than at that of 80 kW m−3. Due to the regeneration of the consumed Fe(II) ions through the irradiation, the amount of ferrous salt to be added can be remarkably reduced. The optimum conditions were obtained with 1.0 x 10−3 mol 1−1 Fe(II) added, a pH value of 3, and a molar ratio of COD :H2O2=1:1. At aCOD volume loading ofless than 0.6 kg m−3 h−1, a COD degradation of more than 70% could be obtained with an energy input of 80 kW m−3.
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A new bipolar electrocoagulation and electroflotation process was developed to treat laundry wastewater. In this new process, electrocoagulation and electroflotation were carried out simultaneously in a single reactor. The operating parameters such as initial pH, hydraulic residence time (HRT) and current density were investigated. The unique design of the reactor made it possible for the effective removal of turbidity, COD, phosphate and surfactant (MBAS) in a wide pH range (5–9) at a short HRT (5–10 min). The pilot scale tests (1.5 m3/h) were carried out successfully in three different places suggested that the bipolar electrocoagulation–electroflotation process was feasible for the treatment of laundry wastewater.
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Oxidation of the nitroaromatic explosives namely, 2,4,6-trinitrophenol (PA), ammonium picrate (AP), 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT) by Fenton's reagent has been investigated in this study. The initial concentrations of nitroaromatics were in the range of 1.0×10−5 to 3.0×10−4M. For the Fenton oxidation of the four nitroaromatics, the structural characteristic is the major factor affecting the decomposition rate rather than the interference effect coming from the oxidation intermediates. Oxidation rate of the explosives in the Fenton process were in the following sequence: DNT>PA>AP>TNT. The results were in good agreement with kinetic model, assuming the pseudo-steady-state hypothesis of hydroxyl radical formed by the Fenton reaction. Thus, a half-life prediction model was proposed and compared with the half-lives calculated from pseudo-first-order equation to prove the interference effect resulted from the oxidation intermediates.
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The effect of temperature was studied on the efficiency of soluble COD removal and bacterial community development during the aerobic biological treatment of a pharmaceutical wastewater. Using wastewater and bacterial inoculum obtained from the full-scale facility treating this wastewater, batch laboratory cultures were operated at 5°C intervals from 30°C to 70°C. Following four culture transfers to allow for bacterial acclimation, residual soluble COD levels were measured and bacterial community fingerprints were obtained by denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction (PCR)-amplified 16S rRNA gene fragments. Soluble COD removal efficiency declined as temperature increased from 30°C (62%) to 60°C (38%). Biological treatment of this wastewater failed to occur at temperatures higher than 60°C. Gradual shifts in bacterial community structure were detected as temperature increased, including a concomitant reduction in the number of different bacterial populations. The impact of temperature on a two-stage biological treatment process was also compared. Better soluble COD removal was achieved when both reactors were operated at 30°C compared to a system where the two stages were consecutively operated at 55°C and 30°C. These results indicate that operation of aerobic biological wastewater treatment reactors at elevated temperatures can have adverse effects on process performance.
Article
The chemical process industries (CPI) must treat wastewaters containing a wide variety of contaminants, ranging from toxic organics like phenol, benzene, other aromatics, formaldehyde, and amines, to inorganics such as sulfite, sulfide, mercaptans, and cyanide, to heavy metals such as hexavalent chrome. These wastewaters also have a wide range of concentrations and combinations of contaminants. The streams must be treated as inexpensively as possible and in a safe manner, preferably by processes that are easy to operate on-site and that require a minimum of labor and technical know-how. And, of course, the ultimate goal of this treatment is that the treated water meet all federal, state, and local discharge regulations. One available wastewater treatment technology that few engineers seem to be familiar with is the Fenton reactor. In this advanced oxidation process, toxic wastewater is reacted with inexpensive ferrous sulfate catalyst and hydrogen peroxide in a simple, nonpressurized (typically batch) reactor to yield (if reacted to completion) carbon dioxide and water. This article offers guidance on the use of this process by first explaining the mechanisms of Fenton`s chemistry and then outlining how to apply it to industrial wastewater treatment.
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In this work, the electrocoagulation process using aluminum and iron electrodes has been used to treat synthetic wastewaters polluted with three different types of pollutant models:  kaolin suspensions, dye solutions, and oil-in-water emulsions. It was obtained that both electrodes can achieve high efficiencies (above 80%) in the treatment of the three wastes. However, there are strong differences in the electrochemical coagulation or breakup mechanism that can be explained in terms of the speciation of the dissolved metals and especially in terms of the significant concentrations of monomeric and polymeric ionic species that appear in the treatment with aluminum electrodes. In every case, sweep coagulation explains the coagulation of kaolin suspension with both aluminum and iron electrodes. However, in the case of aluminum, the neutralization charge mechanism should also be considered for low reagent doses. The coagulation of EBT (Eriochrome Black T) solutions and the breakup of O/W emulsions (oil-in-water emulsions) have been explained by the binding of the pollutants to metal hydroxide precipitates. This binding is promoted for aluminum electrodes because of the adsorption of cationic reagent species on the surface of the aluminum hydroxide.
Article
The removal of pollutants from effluents by electrocoagulation has become an attractive method in recent years. This paper deals with the batch removal of the reactive textile dye Remazol Red RB 133 from an aqueous medium by the electrocoagulation method using aluminum electrodes. The effects of wastewater conductivity, initial pH, current density, stirring rate, dye concentration, and treatment time on the decolorization efficiency and energy consumption have been investigated. Aluminum hydroxypolymeric species formed during an earlier stage of the operation efficiently remove dye molecules by precipitation, and in a subsequent stage, Al(OH)3 flocs trap colloidal precipitates and make solid−liquid separation easier during the flotation stage. These stages of electrocoagulation must be optimized to design an economically feasible electrocoagulation process.
Article
The degradation pathways exhibited by three phenyl-urea herbicides: isoproturon (ISO), chlortoluron (CHLT) and chloroxuron (CHLOX), during photocatalytic (on supported TiO2 under intense solar radiation) and electro-Fenton (EF) treatment were investigated by HPLC coupled to electrospray ionization single and tandem mass spectrometry (HPLC–ESI-MS and MS/MS). In particular, the dependence of degradation efficiency on the initial concentration ratio between substrate and Fe(III) ion was assessed for the EF treatment and a 1:1 ratio was found to be optimal. A comparison between photocatalytic and EF degradation, in terms of structures, number and evolution on a similar time scale (up to 5 h) of by-products, was then performed. Similar reactivities were found in the two cases, hydroxylation (single and multiple, with H, alkyl groups or Cl substitution, depending on the herbicide) and demethylation on the dimethylamino moiety (eventually followed by hydroxylation) being the most relevant processes in by-products generation. The scale of EF degradation efficiency for the three herbicides was almost identical to the photocatalytic one (ISO > CHLT ≈ CHLOX), yet electro-Fenton proved to be a more efficient process, generally leading to a faster further degradation of by-products.
Article
The electrochemical oxidation of 2,4-dinitrophenol (2,4-DNP) aqueous wastes has been studied using both, bulk electrolysis and voltammetric techniques. To carry out the bulk electrolysis, a bench-scale plant with a single compartment electrochemical flow cell was used. Boron-doped diamond (BDD) materials were used as the anode and stainless steel (AISI 304) as the cathode. According to the obtained results, a simple mechanistic model has been proposed. The oxidation of 2,4-DNP leads to the appearance of phenol and quinonic compounds and to the release of the nitro groups from the aromatic ring, in a first step. In a second step, these organics are transformed into carboxylic acids (mainly maleic and oxalic acid). The process ends with the formation of carbon dioxide (CO2). The effects of the waste characteristics (composition and pH) and of the operation parameters of the process (temperature and current density) have also been studied in this work. The complete removal of the organic compounds contained in the waste has been obtained in all essays.
Article
The electrochemical degradation of saturated solutions of herbicides 4-chloro-2-methylphenoxyacetic acid, 2-(4-chlorophenoxy)-2-methylpropionic acid and 2-(4-chloro-2-methylphenoxy)propionic acid in 1 M HClO4 on a boron-doped diamond (BDD) thin film anode has been studied by chronoamperometry, cyclic voltammetry and bulk electrolysis. At low anodic potentials polymeric products are formed causing the fouling and deactivation of BDD. This is reactivated at high potentials when water decomposes producing hydroxyl radical as strong oxidant of organics. Electrolyses in a batch recirculation system at constant current density ≥8 mA cm−2 yielded overall decontamination of all saturated solution. The effect of current density and herbicide concentration on the degradation rate of each compound, the specific charge required for its total mineralization and instantaneous current efficiency have been investigated. Experimental results have been compared with those predicted by a theoretical model based on a fast anodic oxidation of initial herbicides, showing that at 30 mA cm−2 their degradation processes are completely controlled by mass transfer. Kinetic analysis of the change of herbicide concentration with time during electrolysis, determined by high-performance liquid chromatography, revealed that all compounds follow a pseudo first-order reaction. Aromatic intermediates and generated carboxylic acids have been identified using this technique and a general pathway for the electrochemical incineration of all herbicides on BDD is proposed.
Article
A combined electrocoagulation and electroflotation process was designed to reduce Cr6+ to Cr3+ first and then to remove the total Cr from wastewater to a value below 0.5 mg/L. Acidic condition was employed in the reduction of Cr6+ and neutral conditions were found to be beneficial for the coagulation of the precipitates of Cr(OH)3 and Fe(OH)3. The formation of Fe(OH)3 was ensured by sparging compressed air in the coagulation unit through a draft tube. The air not only oxidizes Fe2+ produced electrically, but also helps to mix the water for a better coagulation of the particles. The two-stage electroflotation arrangement can separate the solids from the wastewater to a value of less than 3 mg/L with total Cr less than 0.5 mg/L. The residence time required is about 1.2 h. The optimal conditions for the treatment are: charge loading about 2.5 Faradays/m3 water, pH value in the coagulation unit is 5–8. The power consumption is less than 1 kW h/m3 water at the conductivity of 1.5 mS/cm. When aluminum ions are either added or produced in situ in the coagulation unit, the treated wastewater can be discharged without any filtration.
Article
A novel Electro-Fenton (EF–Fere) method, applied H2O2 and electrogenerated ferrous ion, was investigated for treating the hexamine-containing wastewater. The performance of Fe2+ generation in the electrolytic system was first evaluated, including the factors of the cathode material, initial pH, initial ferric concentration (Fei), and current density. When initial pH exceeded 2.5, the current efficiency dramatically decreased, which was due to the formation of Fe(OH)3. Between 3000 and 10,000 mg/l of Fei, the initial current efficiency of Fe2+ generation was almost constant (85–87%), which dropped sharply to 39% at 1000 mg/l. In EF–Fere experiments, the COD removal efficiency attained above 94% after 5 h of reaction. The relationship between the temperature, dissolved oxygen, and COD was discussed. The changes in hexamine and its oxidation intermediates (methanol, formaldahyde, formate, ammonium and nitrate) during the reaction were also investigated. Three additional experiments using H2O2/Fe2+, H2O2/Fe3+, and direct electrolysis were also conducted to treat the hexamine-containing wastewater for comparison. The results showed that the EF–Fere method was the most efficient.
Article
The electrochemical oxidation of Anthraquinone dye (Alizarin Red S) has been studied on boron-doped diamond (BDD) electrodes on acid medium by cyclic voltammetry and bulk electrolysis. Galvanostatic electrolyses cause complex oxidation reactions that lead to the incineration of Alizarin Red S. The analyses of the chemical oxygen demand (COD) and the total organic carbon (TOC) during the galvanostatic electrolyses at BDD anodes confirm that the electro-oxidation of Alizarin Red S leads to CO2. The complete removal of organic compounds contained in the waste has been obtained at low and high current densities.
Article
Aluminium and iron salts are widely used as coagulants in water and wastewater treatment and in some other applications. They are effective in removing a broad range of impurities from water, including colloidal particles and dissolved organic substances. Their mode of action is generally explained in terms of two distinct mechanisms: charge neutralisation of negatively charged colloids by cationic hydrolysis products and incorporation of impurities in an amorphous hydroxide precipitate (‘sweep flocculation’). The relative importance of these mechanisms depends on factors such as pH and coagulant dosage. Alternative coagulants, based on prehydrolysed forms of aluminium and iron, are more effective than the traditional additives in many cases, but their mode of action is not completely understood, especially with regard to the role of charge neutralisation and hydroxide precipitation. Some basic features of metal hydrolysis and precipitate formation are briefly reviewed and the action of hydrolysing coagulants is then discussed, with examples from the older literature and from some recent studies on model systems. Dynamic monitoring of floc formation and breakage can give useful insights into the underlying mechanisms. Although the results can be reasonably well explained in terms of established ideas, a detailed understanding of the ‘sweep flocculation’ mechanism is not yet available. There are also still some uncertainties regarding the action of pre-hydrolysed coagulants.
Article
This paper reviews the development, design and applications of electrochemical technologies in water and wastewater treatment. Particular focus was given to electrodeposition, electrocoagulation (EC), electroflotation (EF) and electrooxidation. Over 300 related publications were reviewed with 221 cited or analyzed. Electrodeposition is effective in recover heavy metals from wastewater streams. It is considered as an established technology with possible further development in the improvement of space-time yield. EC has been in use for water production or wastewater treatment. It is finding more applications using either aluminum, iron or the hybrid Al/Fe electrodes. The separation of the flocculated sludge from the treated water can be accomplished by using EF. The EF technology is effective in removing colloidal particles, oil & grease, as well as organic pollutants. It is proven to perform better than either dissolved air flotation, sedimentation, impeller flotation (IF). The newly developed stable and active electrodes for oxygen evolution would definitely boost the adoption of this technology. Electrooxidation is finding its application in wastewater treatment in combination with other technologies. It is effective in degrading the refractory pollutants on the surface of a few electrodes. Titanium-based boron-doped diamond film electrodes (Ti/BDD) show high activity and give reasonable stability. Its industrial application calls for the production of Ti/BDD anode in large size at reasonable cost and durability.
Article
The present study is to investigate the treatment of sodium dodecyl sulfate (SDS) surfactant wastewater by the peroxi-electrocoagulation process. The electrochemical oxidation of aqueous surfactant solution has been studied by batch electrolysis experiments. Experiments were conducted to examine the effects of pH, amount of hydrogen peroxide, current density, electrolysis time and time after the peroxi-electrocoagulation, conductivity and surfactant concentration on the surfactant removal. The experimental results showed that SDS in aqueous phase was effectively removed by the peroxi-electrocoagulation method. The batch experimental results revealed that the overall SDS removal efficiency reached 81.6% for initial concentration 60 mg L−1. The optimum current density, optimum pH and electrolysis time were 0.5 mA cm−2, 5 and 10 min, respectively. Mean energy consumption was 1.63 kWh (kgSDS)−1. Results show that the pseudo-second-order equation provides the best correlation for the removal rate of SDS.
Article
The characteristics of restaurant wastewater were investigated. High oil and grease contents were detected. Electrocoagulation was used to treat this type of wastewater. Different electrode materials and operational conditions were examined. Aluminum was preferred to iron. Charge loading was found to be the only variable that affected the treatment efficiency significantly. The optimum charge loading and current density were 1.67–9.95 F/m3 wastewater and 30–80 A/m2 depending on the wastewater tested. The removal efficiency of oil and grease exceeded 94% for all wastewaters tested. The experimental results also show that the electrocoagulation can neutralize wastewater pH. Several mechanisms associated with pH variation are proposed.
Article
The goal of coagulation of fine disperse latex particles of suspensions by dosing with iron ions is to enhance suspension clarification, promote sedimentation and improve their filterability. Two kinds of iron dosing were studied; by directly adding iron chloride or iron sulphate to suspensions or by electrolytic decomposition of iron electrodes (electrocoagulation process, EC). The chemical and electrical processes were examined by varying the pH value and the iron ions concentration in order to determine the optimal operating conditions. To minimise the energy consumption in EC, the suspension conductivity and the current density were varied. This paper shows that flocs in EC-treated suspensions had a higher density and tended to be larger than flocs formed in suspensions dosed with iron chloride or iron sulphate. The kinetics of settling and filtration of EC-treated suspensions were accelerated, demonstrating the interest of EC as an alternative to chemical conditioning.
Article
This study makes a comparison between UV/Nano-TiO(2), Fenton, Fenton-like, electro-Fenton (EF) and electrocoagulation (EC) treatment methods to investigate the removal of C.I. Acid Blue 9 (AB9), which was chosen as the model organic contaminant. Results indicated that the decolorization efficiency was in order of Fenton>EC>UV/Nano-TiO(2)>Fenton-like>EF. Desired concentrations of Fe(2+) and H(2)O(2) for the abatement of AB9 in the Fenton-based processes were found to be 10(-4)M and 2 x 10(-3) M, respectively. In the case of UV/Nano-TiO(2) process, we have studied the influence of the basic photocatalytic parameters such as the irradiation time, pH of the solution and amount of TiO(2) nanoparticles on the photocatalytic decolorization efficiency of AB9. Accordingly, it could be stated that the complete removal of color, after selecting desired operational parameters could be achieved in a relatively short time, about 25 min. Our results also revealed that the most effective decomposition of AB9 was observed with 150 mg/l of TiO(2) nanoparticles in acidic condition. The effect of operational parameters including current density, initial pH and time of electrolysis were studied in electrocoagulation process. The results indicated that for a solution of 20 mg/l AB9, almost 98% color were removed, when the pH was about 6, the time of electrolysis was 8 min and the current density was approximately 25 A/m(2) in electrocoagulation process.
Article
Electrocoagulation is an electrochemical wastewater treatment technology that is currently experiencing both increased popularity and considerable technical improvements. There has been relatively little effort to better understand the fundamental mechanisms of the processes, particularly those that could provide design parameters to optimize the performances of this relatively simple and inexpensive technique. In a research programme to delineate the mechanisms of the fundamental processes involved in, the authors have realized that the technology has been insufficiently reviewed with emphasis on the fundamentals and their relationship to the performance of this technology. This paper presents an in-depth discussion and consideration of the factors that need to be addressed for optimum performance of this technology. Recent improvements of this technique and the theoretical model studies are also reviewed.
Article
Electro-Fenton denitrification of a model wastewater was studied using platinized titanium electrodes in a batch electrochemical reactor. The model wastewater was prepared from components based on the real aquaculture effluent with nitrate concentrations varying from 200 to 800 mg L(-1). The technical as well as scientific feasibility of the method was assessed by the relationship between the most significant process variables such as various Fenton's reagent to hydrogen peroxide ratios (1:5; 1:20 and 1:50) and current densities (0.17 mA cm(-2), 0.34 mA cm(-2) and 0.69 mA cm(-2)) and their response on denitrification efficiency in terms of nitrate degradation using central composite Box-Behnken experimental design was determined. The goodness of the model was checked by the coefficient of determination R(2) (0.9775), the corresponding analysis of variance P>F and a parity plot. The ANOVA results indicated that the proposed model was significant and therefore can be used to optimize denitrification of a model wastewater. The optimum reaction conditions were found to be 1:20 Fenton's reagent/hydrogen peroxide ratio, 400 mg L(-1) initial nitrate concentration and 0.34 mA cm(-2) current density. Treatment costs in terms of electricity expenditure at 0.17, 0.34 and 0.69 mA cm(-2) was 7.6, 16 and 41.8 euro, respectively, per kilogram of nitrates and 1, 2 and 4 euro, respectively, per cubic meter of wastewater.