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Decolorization of Levafix Brilliant Blue E-B by Electrocoagulation Method
Environmental Progress & Sustainable Energy
Abstract
In this study, the decolorization of Levafix Brilliant Blue E-B by electrocoagulation method using aluminum and iron electrodes was investigated. The influence of the operating variables such as current density, initial pH, time of electrolysis, supporting electrolyte concentration on decolorization efficiency, and energy consumption was determined. The results show that aluminum electrode (Al) was more effective than iron (Fe) electrode in terms of decolorization efficiencies and operating costs. When the aluminum electrode was used, 99% decolorization was obtained at current density of 100 A/m2, initial pH of 5.5, electrolyte concentration of 5 mM, and electrolysis time of 20 min. The corresponding energy consumption and operating cost were found as 16.9 kWh/m3 and 2.921 $ per m3, respectively. © 2010 American Institute of Chemical Engineers Environ Prog, 2011
... Similar work was reported for removal of dyes with electro-coagulation. In removal of levafix brilliant blue using aluminum and iron electrodes, 97.8% of dye was removed at 200 A/m 2 current density and 10 min reaction time [20]. In another work for removal of Indigo Carmine dye with iron electrode after 3 h of electrocoagulation a 96% decolorization rate was reported at 10.91 A/m 2 and 99.9% removal efficiency at 54.57 A/m 2 after 60 min contact time [21]. ...
... In removal of Levafix Brilliant Blue using aluminum and iron electrodes, higher energy consumption was observed for iron electrode rather than aluminum electrode. In addition, it is reported that for complete dye removal (100%), 34kWh/m 3 was used at 200 A/m 2 current density [20]. In another work for removal of Acid Red 14, it is reported that with increases in inter-electrode distance no significant effect on the efficiency of color removal was observed. ...
... Similar results were reported for removal of Acid Red 14 [18], levafix brilliant blue E-B [20] and orange II [22]. In addition, the final solution pH was increased for both electrodes which this increases were higher for iron electrode rather than aluminum electrode. ...
ABSTRACT: In this study, removal of methylene blue by electro-coagulation method using aluminum and iron electrodes was investigated. The influence of the operating parameters such as contact time, current density, anode type, inter-electrodes distance, initial and final pH and energy consumption rate was determined. Dye removal was increased with increases in solution pH, current density and contact time and then decreased for increase in initial dye concentration and electrodes distance. The results show that the electrochemical method has significant efficiency in removal of methylene blue, higher efficiency was observed for iron (Fe) electrode; namely 100% and 95.78% of dye was removed by iron and aluminum electrode; respectively, after 24 min contact time. For a given current density, the removal efficiency and energy consumption rate showed that iron electrode was superior to aluminum in removal of methylene blue. In the case of iron as anode type, the required energy for complete dye decolorization was 3.8 kWh/m3; for 98% dye removal, the required energy was observed to be 4.3kWh/m3 in the case of aluminum as anode type. In general, complete methylene blue can be removed at operating parameters condition of iron as anode, distance between electrodes of 1cm, solution pH of 9 and current density of 50 A/m2 for 24 min electro-coagulation time.
... At pH 6.5, greater removal of cadmium and nickel was observed with aluminum electrodes; at pH 8.5, greater removal was seen with iron electrodes (Fig. 10). Over the years, electrocoagulation has been found to be a vital technology for removal of various types of dyes from wastewater [283,284,[293][294][295][296][297][298][299][300][301][302]285,[303][304][305][306][307][308][309][310][311][312]286,[313][314][315][316][317][318][319][320][287][288][289][290][291][292]. Acid dyes, basic dyes, reactive dyes, disperse dyes, azo dyes, and sulfur dyes have all been removed via electrocoagulation [283,284,[293][294][295][296][297][298][299][300][301][302]285,[303][304][305][306][307][308][309][310][311][312]286,[313][314][315][316][317][318][319][320][287][288][289][290][291][292]. ...
... Over the years, electrocoagulation has been found to be a vital technology for removal of various types of dyes from wastewater [283,284,[293][294][295][296][297][298][299][300][301][302]285,[303][304][305][306][307][308][309][310][311][312]286,[313][314][315][316][317][318][319][320][287][288][289][290][291][292]. Acid dyes, basic dyes, reactive dyes, disperse dyes, azo dyes, and sulfur dyes have all been removed via electrocoagulation [283,284,[293][294][295][296][297][298][299][300][301][302]285,[303][304][305][306][307][308][309][310][311][312]286,[313][314][315][316][317][318][319][320][287][288][289][290][291][292]. Meanwhile, dye removal efficiencies depend on operating conditions and therefore, electrocoagulation has been combined with other advanced oxidation processes (AOPs) in many recent studies in order to achieve efficient treatment. ...
Research and development activities on standalone systems of membrane bioreactors and electrochemical reactors for wastewater treatment have been intensified recently. However, several challenges are still being faced during the operation of these reactors. The current challenges associated with the operation of standalone MBR and electrochemical reactors include: membrane fouling in MBR, set-backs from operational errors and conditions, energy consumption in electrochemical systems, high cost requirement, and the need for simplified models. The advantage of this review is to present the most critical challenges and opportunities. These challenges have necessitated the design of MBR derivatives such as anaerobic MBR (AnMBR), osmotic MBR (OMBR), biofilm MBR (BF-MBR), membrane aerated biofilm reactor (MABR), and magnetically-enhanced systems. Likewise, electrochemical reactors with different configurations such as parallel, cylindrical, rotating impeller-electrode, packed bed, and moving particle configurations have emerged. One of the most effective approaches towards reducing energy consumption and membrane fouling rate is the integration of MBR with low-voltage electrochemical processes in an electrically-enhanced membrane bioreactor (eMBR). Meanwhile, research on eMBR modeling and sludge reuse is limited. Future trends should focus on novel/fresh concepts such as electrically-enhanced AnMBRs, electrically-enhanced OMBRs, and coupled systems with microbial fuel cells to further improve energy efficiency and effluent quality.
... In terms of removal efficiency and operating costs, the core findings found that the aluminum electrode (Al) was more effective than the iron electrode (Fe). At 100 A/m2 of current density, 5.5 of initial pH, 5 mM of electrolyte amount, and 20 min of electrolysis time, 99 percent decolorization was attained using aluminum electrodes [65]. ...
A huge amount of textile wastewater is discharged annually to the environment from numerous industrial activities as raw wastewater or without proper treatment that must be treated efficiently. Several conventional methods have been used to remove pollutants from textile wastewater based on their action mechanisms, i.e. physical, chemical, biological, and their integration, such as precipitation, biological, filtration, and their integrations. But these methods suffer from significant drawbacks. For example, the sedimentation method has very low removal efficiency for dyes. Also, filtration either very weak in removal efficiency if we talked about conventional filtration like cloth media filtration and media filtration while others like membrane filtration make cost more money. The conventional chemical may consume a lot of chemicals and is hardly applicable regarding chemicals handling, transportation, and storage. The biological processes are mostly non-efficient for direct treatment of dye wastewater because of the hard biodegradability and toxicity of the dyes pollutant to the microorganisms plus nutrients requirement since dyes wastewater may have limited nitrogen and phosphorus. Electrochemical wastewater remediation technologies received much attention in recent years. Electrocoagulation technology (EC) is a practical electrochemical method that is used to treat different kinds of wastewater containing numerous types of contaminants including dyes. This paper aims to review the process mechanisms, reactor, and process design factors, electrodes configuration, treatment efficiency, application and case studies, and finally the economy of applying the electrocoagulation for textile or dye wastewater treatment. This work also summarizes the core results of the publications reviewed. The main findings of this paper proved that EC technology is eco-friendly, cost-effective, and high efficient in dye removal.
... Increases in dye removal at higher pH values may be due to the nature of the reaction between Al +3 ions and hydroxide ions. Similar results were reported for the removal of Acid Red 14 (Khandegar and Saroha, 2013) Levafix Brilliant blue E-B (Akbal and Kuleyin, 2011) and Orange II (Daneshvar et al., 2003) ending on the pollutant's nature and the treatment efficiency (Kim et al., 2002). ...
Large-scale textile industries used large amounts of toxic chemicals which are very hazardous to human health and environmental sustainability. In this study, the removal of various dyes from effluents of textile industries using the electrocoagulation process was investigated. The studied dyes were Reactive Red 120 (RR-120), Basic Blue 3 (BB-3), and Basic Red 46 (BR-46), which were found in samples collected from effluents of three major textile factories in the Amhara region, Ethiopia. For maximum removal, the dye BB-3 required acidic pH 3, RR-120 basic pH 11, while BR-46 neutral pH 7 conditions. BB-3 required a longer treatment time of 80 min than BR-46 and RR-120, which required 30 and 40 min, respectively. The best removal efficiency of 99.5%, 93.5%, and 96.3% was achieved for BR-46, BB-3, and RR-120, respectively, from synthetic wastewater containing 10 mg l-1of each dye at an applied potential of 10 V. The method was applied to real textile wastewaters and 73.0 to 99.5% removal of the dyes was achieved, Indicating Electrocoagulation can be used as a simple, and reliable method for the treatment of real wastewater from textile industries. It is used as a potentially viable and inexpensive tool for the treatment of textile dyes Analysis of the electrochemically generated sludge by X-ray Diffraction, Scanning Electron Microscope, and Fourier Transform Infrared Spectroscopy revealed the expected crystalline aluminum oxides (bayerite (Al(OH)3 diaspore (AlO(OH)) found in the sludge. The amorphous phase was also found in the floc. Textile industry owners should be aware of the impact of the discharge of effluents on the Ecosystem and should use the investigated electrocoagulation method for effluent treatment before discharging into the environment.
... These findings are consistent with those of Neppolian et al. [40] and Hussein [41] in the treatment of textile wastewater effluents with photocatalysts and solar energy. In the treatment of synthetic coloured wastewater, Akbal [42] discovered that UV light had a higher detoxification rate than sun irradiation. ...
In this study, the Fenton/adsorption of dye effluent containing Levafix blue dye has been carried out via a cost-efficient and eco-friendly heterogeneous Fenton and solar-Fenton methods. Alum sludge, the water treatment by-product were successfully collected and calcined to 400 °C (AS400) were tested for use as a catalyst in the Fenton process. X-ray diffraction, Scanned electron microscopy techniques were applied to investigate the structural and morphological properties of such catalyst. The results showed that the material had a better photocatalytic activity under sunlight irradiation. The process of solar photo-Fenton reagent including AS400 was found to be competent for the oxidation of Levafix dye compared with the process of using Fenton process. The oxidation was improved to a great extent from 60 to 99% removal in the treatment time of 40-min irradiation. The key factor is containing 1.5 g/L and 800 mg/L of AS400 and H 2 O 2 , respectively, at pH 3.0. As a result, the practical application of such a by-product as a catalyst on the Fenton system employing natural solar radiation on the treating dye effluent indicates that technique is extremely efficient for a safer environment.
... where £ is the price of electrical energy for industrial sector and it was 0.05 US$/1 KWh in June 2019, ß is the price of the iron electrodes that was 0.5 US$/1 m 3 in the Egyptian market, V is the applied voltage, I is the applied current, t is the time, v is the working volume, Mw is the molecular mass, n signifies the number of electrons transferred and F is corresponding to Faraday constant. The TOC was found to be 1.115 US$/m 3 , which is considered an economic value compared to a previous work done on the removal of Levafix Brilliant Blue E-B by EC technique using Fe electrode, which costed about 1.526 $/m 3 in the Turkish market in 2011 (Akbal & Kuleyin, 2011). Furthermore, the removal of AG20 dye using Fe electrode plates costed 1.45 US$/m 3 in Egypt (Shaker et al., 2020). ...
Our study considers the influence of a different electrode shape on the removal percentage of Reactive Yellow 17 (RY17) dye. The anode is a PVC tube with an iron net wrapped around the tube with a surface area of 95.88 cm², while the cathode is a stainless-steel tube with a surface area of 118.2 cm² for each cathode. Many factors were taken into account like pH, current density (CD), effect of supporting electrolytes and the effect of temperature. Under optimum conditions, the removal efficiency has reached 99.8%. The thermodynamic parameters showed the spontaneity of the mechanism of removal. The energy consumption and cost of operation were 21.7 kWh/kg dye and 1.115 US$/m³, respectively.
... This observation is most likely due to the maximal OH • radicals' production within the acidic medium. However, unfavourable radicals are created at higher pH values causing decrease in the degradation rate [27,28]. The reason that Fe 3 O 4 -based Fenton system behaved differently at different solution pHs could be related to the production of the ˙OH radicals. ...
‘Ultraviolet’ and ‘Solar’ wastewater treatment units are used augmented with nanocrystals of magnetite, Fe2O3, which were previously synthesised via a cost-efficient co-perception route. The nanocrystals produced were used as a Fenton reagent source for the oxidising carbamate pesticide in aqueous solution through a combination of natural abundant solar radiation as well as artificial UV source. System parameters were examined and the optimal operating conditions were investigated to maximise the system yield. The objective optimisation was attained using a Box-Behnken factoring design (BBD) based on Response Surface Methodology, RSM. A mathematical model was developed and the maximal removal efficiency reached to 84.1% within 15 min of reaction time. Furthermore, the chemical oxygen demand was then investigated and it was oxidised and deduced to 57%. Analysis of the experimental data revealed that a second-order reaction model is best described the reaction kinetics. The calculated thermodynamic parameters suggested that the non-spontaneous nature of oxidation at high temperature was corroborated by positive Gibbs free energy change ∆G• and negative entropy, ∆S• values. Also, the negative values of enthalpy, ∆H•, indicated that the reaction was exothermic. The low activation energy barrier (−35.85 kJ/mol) indicated that the reaction proceeds at a low energy level.
... The soluble and colloid contaminants are adsorbed on the coagulant and can then be removed by sedimentation. The flotation process was occurred at the same time in the system on the cathode's side after generating a gas bubble to carry the light particles to the surface of the reactor [5,6]. ...
The present work focused on the development and evaluation of a compact electrocoagulation (EC) reactor, combined between EC and clarifier processes in continuous modes for decolorization and turbidity removal, named the integrated electrocoagulation-sedimentation reactor (IECS). The experiments were firstly conducted in the four-liter batch column in order to optimize the EC configuration and operation condition. The removal kinetics were also investigated and predicted for kinetic correlations. After various optimization steps, the IECS reactor was conducted, consisting of EC and clarifier compartments. Liquid flow pattern in EC compartment was examined through resident time distribution technique for defining the number of EC units and divided baffles. In summary, four units of EC were placed in the EC compartment of the IECS reactor with 90% in the width of three baffles. Each EC unit had two pairs of aluminum electrode plats in monopolar arrangement with a 1.5 cm gap and required a current density of 13.5 mA/cm². For the clarifier compartment, it was mainly designed based on the batch settling test for separating the precipitated particles. The treatment performance of the IECS reactor was tested at different liquid flows in order to reduce the pollutant to a certain level. For the individual condition, liquid flow rates of 3 and 1 L/min were defined for turbidity and color, respectively. If both pollutants are presented simultaneously, a liquid flow rate of 1–2 L/min can be used for decreasing turbidity from 250 to <20 NTU and color from 6000 to <300 ADMI.
... This observation is most likely due to the maximal OH • radicals' production within the acidic medium. Hwover, unfavourable radicals are created at higher pH values [15,16]. In Menoufia Governorate in the north of Egypt in the Nile Delta Region, like most cities in Egypt, well endowed with the natural solar radiation especially in the sum season the sun enhanced Fenton oxidation experiments is conducted. ...
Abstract: Pesticides are attained through the environment via a direct discharge of the agriculture stream in massive amounts. Basically, the precise estimation of pesticide release into the ecosystem is quite uncertain. But, recent studies state its toxicity to the biosphere. Thereby, treating such effluent is a must. Heterogeneous catalytic oxidation systems showed a superior activity due to in-site oxidation. Magnetite nanocrystals (Fe3O4) were synthesized using a cost-efficient co-precipitation technique and the structure and morphology of the nanostructured particles were studied using X-ray diffraction (XRD) characterized and transmission electron microscopy (TEM). The produced Magnetite was used as a source of Fenton’s reaction for oxidizing methomyl in aqueous stream. The effect of multivariable system parameters were investigated, and the optimal system conditions were monitored at pH 3.0 and 100 and 40 mg/L of H2O2 and, magnetite, respectively which recorded 72% of mehtomyl removal within 80 min time of reaction at a lab-scale ultraviolet reactor. To add up, for large scale applications, parabolic trough solar concentrator mounted with a tubular reactor is used in a pilot scale facility during the summer periods in Menoufia Governorate, Egypt to conduct the solar experiments which recorded a hgher removal efficiency through augmented facility.
... Also, the removal of Levafix Brilliant Blue E-B by the EC technique using the Al electrode has cost about 1.501 $/m 3 and about 1.526 $/m 3 for Fe electrode in the Turkish market in 2011 [51]. Table 11 includes a comparison between the results of the present work and the results found in the previous work of different dyes (especially the acid dyes) with different reactors' configurations and different connections of different types of electrodes and other conditions. ...
The present work focuses on the effectiveness of the electrocoagulation technique for the removal of single and binary models of Acid Green 20 (AG20) and Reactive Yellow 17 (RY17) using aluminum electrodes in a batch stirred bi-polar reactor. It was found that the optimum conditions for both models leading to the higher percent removal of the dyes were; pH 2.1, 40 mA/cm² current density, 0.5 g/L of sodium chloride, and temperature 45 °C. The removal has reached 92.2% and 86.5% in the binary model for RY17 and AG20 and in the single model the removal was 95.4% and 92.7% for RY17 and AG20 dyes respectively. The thermodynamic parameters and adsorption models were evaluated.
... The aluminum electrode achieved 99% decolorization in less than 30 min at a current density of 100 A/m 2 , electrolyte concentration of 5 mM, and initial pH of 5.5. The operational cost and energy usage were calculated to be as $2.9 per m 3 and 16.9 kWh/m 3 , respectively (Akbal et al. 2011). ...
Dyes and pigments are complex organic molecules that are widely utilized in different industries leading to effluent discharge, thus polluting water and disturbing the aquatic life. A wide range of physicochemical and biological methods have been introduced for the dye remediation. Constant research developments over the last decade resulted in the evolution of traditional physiochemical methods into advanced oxidation processes. Likewise, biological treatments have also advanced from using microorganisms to biocatalysts and integrated biochemical approaches for dye remediation.
... These are generally: trapping, adsorption, neutralization/destabilization of charges and complexation/precipitation. [57,58] In this study, to gather the main reactions of EC, the species formed at different pH, the adsorbent species (Al(OH) 3 ), and the adsorbate (AR.14), it was wise to present simultaneously the different possible mechanisms linking the adsorbent to the adsorbate. Since the water to be treated forms a molecular solution and not colloidal, the explanations by trapping mechanisms and neutralization/destabilization of the charges were excluded. ...
Electrocoagulation process was applied for the removal of Acid Red 14 in bath essays. Under optimal operating conditions: current density of 70 mA/cm², 60–90 min of reaction, natural pH, and an initial concentration of 50 mg/L, the decolorization and COD removal efficiencies were 95% and 90%, respectively. The electrical energy consumption was 110 kWh/kgAR.14removed. These experimental results are well modeled by the Langmuir and Freundlich isotherms and follow first-order reaction kinetics. The thermodynamic parameters indicated that the nature of the adsorption process was endothermic and spontaneous. The mud formed after electrocoagulation was characterized by FTIR and SEM coupled to EDS.
... Calculated power consumption regarding Fe/Fe, Fe/Al, Al/Al, and Al/Fe was 42.62, 51.73, 40.79, and 41.70 Wh/L, respectively. Akbal et al. [86] studied the removal of Levafix Brilliant Blue E-B by electrocoagulation and claimed that Al/Al had a higher efficiency than Fe/Fe. Aluminum electrode preferred electrode material due to the higher removal efficiency and lower energy consumption than the iron electrode, and all subsequent experiments were carried out with aluminum electrode. ...
The present study recommends the electrocoagulation (EC) technique as a possible-green option to the conventional process for the efficient removal of ibuprofen (IBU) from drinking water for the first time, investigating a thorough analysis by optimizing operational parameters and kinetics/isotherms models. Under the optimum conditions 63% of IBU was removed. The double-stage electrocoagulation resulted in the removal efficiency of 73.8%. The dynamic and equilibrium data followed first-order and Freundlich. The treatment cost of IBU removal by electrocoagulation would be 1.8 US $/m3. It is possible to consider the EC technique as the promising IBU removal method.
... The soluble and colloid contaminants are adsorbed on the coagulant and can be removed by sedimentation then. The flotation process was occurred at the same time in the system on the cathodes side 7 th International Conference on Environmental Engineering, Science and Management Centara Hotel & Convention Centre, Udon Thani, Thailand, May 24-25, 2018 after generating gas bubble to carry the light particles to the surface of reactor [4,5]. It is commonly applied for both water and wastewater treatment processes. ...
This study aimed to design and evaluate the new electrocoagulation reactor (ECR) for treating dye and turbidity from synthetic textile wastewater. The experiments were initially conducted in batch column reactor in order to optimize the electrodes configuration and operation condition including electrodes type, arrangement (mono- or bipolar), gap, and current density. The optimization analysis result showed that the monopolar connection within inner gap 1.5 cm and current density 1.5 mA/cm2 were contained as the optimal condition in terms of gas flow rate over electrode loss ratio. It was then studied the removal kinetic of the design parameters for ECR such as hydraulic retention time (HRT), optimal current density, and overflow rate (OFR). Removal kinetic was studied with initial concentration 250 NTU and 6,000 ADMI of reactive dye. The optimal current density 4.5 mA/cm2 was obtained with detention time of EC about 25 to 30 minutes in order to achieve the treatment efficiency of 95% for both bentonite and dye. Moreover, the comparative analysis between electrocoagulation (EC) and chemical coagulation (CC) was examined. Both EC and CC are possibly used for removing turbidity and color, however, the economization will be subsequently studied. Estimation of the treatment cost through both processes was examined. It can be concluded that if there was only turbidity in wastewater with low concentration, about 50 NTU, conventional system is preferred. However, it is usually co-existed with color and high concentration. Therefore, EC is more suitable for treating turbidity and color from textile wastewater in terms of economics for high initial concentration. ECR was finally designed in rectangular shape, which was combined of EC and separation process in continuous operation. ECR can remove turbidity and dye up to 95% (3 LPM) and 97% (1 LPM), respectively. Moreover, residual time distribution (RTD) was studied to identify the flow behaviors in ECR.
... Industrial effluents from many industries contain high amounts of heavy metal ions, such as chromium, cadmium, copper, zinc, nickel, gold and silver which are nonbiodegradable and they are known to be toxic and carcinogenic. Different separation techniques could be used as precipitation, ion exchange, adsorption, electro-dialysis and filtration [2][3][4][5][6][7]. Such techniques are generally multistep, time consuming and require extensive equipment, chemicals and handling [8][9][10][11]. ...
The electrokinetic of chromium, copper, silver and gold ions removal from synthetic and wastewater via electro-flotation was investigated. Kinetics and thermodynamic parameters of the electro-flotation process were determined. The effect of initial pH and metal ion concentration, treatment time and temperature showed that the maximum removal was achieved at pH 6. The order of the metal ions removal is Cr 3+ > Cu 2+ > Ag + > Au +. The removal process follows pseudo first-order kinetics and the adsorption is a heterogeneous system characterized by physical adsorption which is exothermic. Negative values of entropy change ∆S° and Gibbs free energy change ∆G° indicate that this adsorption process is spontaneous and less favorable at high temperatures. The treatment of electroplating wastewater showed that the removal efficiency was ranging between 96-99%. The electrical energy consumption was 0.033 Kwh/L.
... Aynı deney koşullarında paslanmaz çelik elektrodun demir elektroda nazaran daha az aşındığı ve daha az çamur ürettiği gözlenmiştir. Akbal ve Kuleyin[35] tarafından yapılan diğer bir çalışmada ise Al elektrotun Fe elektrottan daha etkin olduğu rapor edilmiştir. 8A). ...
Tekstil boyama endüstrisinde kullanılan Bazik Mavi 3 boyarmaddesinin alüminyum elektrot kullanılarak elektrokimyasal olarak tekstil atık sularından giderimi üzerinde çalışılmıştır. Kesikli proses ile yapılan deneyler sonrasında 10 dakika sonunda pH8 değerinde %97’den fazla giderim etkinliği hesaplanmıştır. Elektrokimyasal işlemin 6. dakikası sonunda 50-400 mg/L aralığındaki konsantrasyonlardaki boya giderim etkinliği %92-95 arasında değişirken bu oran, 500 ve 600 mg/L için sırasıyla %72 ve %60 olarak hesaplanmıştır. 10. dakika sonunda ise bütün konsantrasyon değerlerindeki boya giderim oranı %96 civarındadır. Akım yoğunluğu değerlendirildiğinde ise boya giderim etkinliği 333 A/m2 akım yoğunluğu ile 4. dakikadan sonra (%96) işlem bitene kadar çok fazla bir artış göstermemiş ve 10. dakikada %97 seviyesine ulaşmıştır.
... Low voltage direct current electrocoagulation is one of the techniques that has been extensively studied [2][3][4] . The electrocoagulation technique typically removes 98-100% of color in dye-containing wastewater [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] . Surface complexation and electrostatic attraction between dye molecules and the electroactive monomeric ions, metal hydroxides and polymeric hydroxyl complexes, are the underlying mechanism for color removal in the electrocoagulation technique [24] . ...
A sparged packed-bed electrocoagulator was developed for decolorization of dye wastewater. The anode of the electrocoagulator was a perforated polyvinyl chloride (PVC) pipe packed with iron nuts. At the center of each anode, a gas sparging tube was installed, and the hydrogen generated from the oxidation reduction reactions was recycled back to the reactor as the sparging gas. When running with a DC power supply, the operation of the packed-bed electrocoagulator with gas sparging can both enhance the decolorization efficiency and reduce the resistance and the energy consumption of the operation. When running with a photovoltaic (PV) panel, the wastewater feed flowrate was adjusted in response to the varying PV output current. The gas sparging was found to help enhance mass transfer rates of the electroactive ions to the bulk solution, and to make the decolorization efficiency independent of the varying feed flowrates.
... The electrochemical method has proved to be effective in organic degradation, including aromatic compounds (Li et al. 2010). Indeed, electrochemical method has been successfully tested and it has certain significant advantages such as simple equipment, easy operation and lower operating cost (Dirany et al. 2012, Akbal et al. 2011, Chu et al. 2013, Hongzu et al., 2007. The process requires significantly less equipment than conventional biological treatment processes , Li et al. 2008). ...
The indirect electrochemical method for pulp and paper mill industrial dyes was studied by using graphite carbon electrodes in laboratory scale. During the process, degradation of the chromoporic groups and aromatic rings of the dyes were proved by this method. The degradation of the dyes was followed using UV-Vis spectroscopy, LCMS, COD and TOC measurements. The maximum removal efficiency of colour 97% and 95%, chemical oxygen demand (COD) of 95% and 90% and total organic compound (TOC) of 95% and 97% could be achieved for the dyes at 2.5 g L-1 of NaCl concentration, Current density of 340 A m −2 and at pH 3 for Basic green 1 and Direct Green 26, respectively. The effect of initial pH, supporting electrolyte and current density on the degradation of dye was discussed. The results revealed the suitability of the present process for the effective degradation of dyes pulp and paper mill dyes.
... A number of specific dyestuffs have been investigated, e.g. orange II [9], acid orange 7 [10], acid yellow 36 and 23 [11,12], reactive yellow 84 [13], acid red 14 [14], reactive black 5 [15], direct red 23 [16], acid red 2 [17], acid green 50 [18], crystal violet [19], acid blue 29, reactive red 2, acid red 97, reactive blue 4 [20], reactive blue 140 [21], reactive blue 29 [22], reactive orange 84 [23] and real wastewater containing dyes [24][25][26][27]. In both batch and continuous flow reactors, the decolorization efficiency has been found to depend on the initial pH, the dye concentration, and the applied current density. ...
A batch electrocoagulator was developed for optimal removal of reactive blue 21 from wastewater. The data from the batch reactor were then used to develop a continuous-flow reactor with similar performance for reduction of chemical oxygen demand (COD) and color removal. In the 1.8-L batch system, COD removal of 90% and color removal of 95% were achieved using a current density of 30 A/m2, electrode area of 0.10 m2, and electrocoagulation time of 7 min. The continuous-flow electrocoagulator consisted of two hollow iron tubes put together in a concentric configuration with a working volume of 1.5 L and an effective electrode area of 0.15 m2. By keeping the current density and the applied electric charge the same in both the batch and the continuous-flow systems, the COD and color removals and energy consumption of both systems were the same within 10%. However, the color and COD removals by the batch reactor were higher than those of the continuous-flow electrocoagulator because the distribution of electroactive species in the batch reactor was more effective than that in the tube-in-tube electrocoagulator.
... The main advantages of electrocoagulation over other conventional techniques, such as chemical coagulation and adsorption, are "in situ" delivery of reactive agents, no generation of secondary pollution, and compact equipment. The earlier studies have reported the potential of electrocoagulation to treat a variety of industrial and domestic wastewater [22][23][24]. ...
... Therefore, a lot of researchers have focused on the efficiency of the system on different aqueous solutions in terms of various experimental conditions. Although many researches on treatment of synthetic or real wastewaters with EC are available, very few researches have been carried out on the economical applicability of EC in details [20][21][22]. ...
In this study, two case studies were carried out: Electrocoagulation (EC) of a reactive textile dye solution and a textile wastewater. Stainless steel (SS) and iron (Fe) electrodes were used as sacrificial electrodes in parallel connection modes. Effects of pH, current density, and operating time on performance of EC were investigated. Optimum parameters obtained from dye experiments were applied to treatment of the textile wastewater. According to the experimental results, SS electrodes were found to be superior compared with Fe electrodes for treatment of both the dye and the textile wastewater. By using SS electrodes, the textile wastewater was electrocoagulated successfully with 89.7% of COD, 91.2% of TOC, 90.3% of turbidity, and 94.1% of TSS removal efficiencies as well as 2.43 kWh/m3 of energy and 0.05 kg/m3 of electrode consumptions, 1.061 kg/m3 of sludge production, and 0.62 $/m3 of total operating cost. © 2011 American Institute of Chemical Engineers Environ Prog, 32: 60–68, 2013.
... A number of specific dyestuffs have been investigated, e.g. Orange II [9], Acid Orange 7 [10], Acid Yellow 23 [11,12], Reactive Yellow 84 [13], Acid Red 14 [14], Reactive Black 5 [15], Direct Red 23 [16], Acid Red 2 [17], Acid Green 50 [18], Crystal Violet [19], Acid Blue 29, Reactive Red 2, Acid Red 97, Reactive Blue 4 [20], Reactive Blue 140 [21], Reactive Blue 29 [22], Reactive Orange 84 [23] and real wastewater containing dyes [24][25][26][27]. In both batch and continuous flow reactors, the decolorization efficiency has been found to depend on the initial pH, the dye concentration, and the applied current density. ...
This paper deals with the development of a reduced-cost electrode as a substitute for a plate or tubular electrode. A polyvinyl chloride (PVC) tube with an internal diameter of 28 mm was packed with machine shop turnings. The packed bed had an apparent density of 493 kg/m(3). The PVC tube had distributed 5 mm-holes on its surface to allow the transport of metal ions from the electrode to the bulk solution. Various electrical current and electrocoagulation times were investigated for achieving high color and Chemical Oxygen Demand (COD) removals. The required electrical current and electrocoagulation time for achieving a maximum color removal of 98% and a maximum COD removal of 93% were found to be 0.9 A and 10 min. The performances of the packed-bed anode electrocoagulator were compared with those of a conventional tubular iron anode electrocoagulator. It was found that the removal efficiencies of the packed-bed anode were higher than those of the tubular anode for the first 8 min. The higher removal performances of the packed-bed anode may be due to its higher surface area for the distribution of the electroactive species. However, at the optimal electrocoagulation time of 10 min, the energy consumption for the packed-bed anode (0.50 kWh/m(3)) was higher than that of the tubular anode (038 kWh/m(3)). The higher electrical energy consumption of the packed-bed electroagulator was expected to be due to the increased resistance associated with increased concentration overpotential (volt) for this anode.
... Textile industry generates large volumes of wastewater originating from dying and finishing processes. In addition, dyehouse effluents contain significant amounts of hazardous compounds [1][2][3][4][5]. Therefore, novel treatment techniques providing not only pollutant removal but also having potential to supply process water have been a matter of considerable interest in textile industry. ...
Reducing water demand in textile sector is one of the important environmental concerns. In this study, individual and combined effects of selected operational parameters on a full-scale electrochemical oxidation (ECO) process treating dyehouse effluent were investigated experimentally. Combinations of variables including current density, wastewater pH, and conductivity resulting in maximum color removal efficiency were determined using the Box-Behnken design method. In addition to color removal, variations in wastewater organic composition before and after ECO were also examined critically. Removal and/or generation of 22 polycyclic aromatic hydrocarbons (PAHs) before and after ECO were investigated under variable operational conditions. Treatability of ECO effluent using conventional activated sludge process was investigated by both full-scale monitoring studies and batch-scale nitrification tests. Toxicity impact of raw, ozonized, and electrochemically treated wastewaters on nitrifiers were also determined and compared. Water reuse and salt recovery alternatives were assessed by full-scale tests in a pilot plant which is composed of nanofiltration (NF), reverse osmosis (RO), and activated sludge processes. Advantages and disadvantages of applying ECO process as a pretreatment prior to membrane-based or biological methods were critically evaluated. The average flux values of NF and RO membranes without ECO were 39 ± 2 and 19.5 ± 1 L m−2 h−1, respectively. The average flux values of NF and RO membranes without ECO were 39 ± 2 and 19.5 ± 1 L m−2 h−1, respectively. The permeability of the membranes for raw dyehouse effluent (without ECO) were estimated to be 6.0 ± 11 and 0.73 ± 0.6 L m−2 h−1 bar−1 Another important observation was formation of some PAHs including naphthalene, acenaphtylene, anthracene, benzo(a)anthracene, and benzo(g,h,i)perylene as a function of operational conditions maintained in ECO process. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 472–481, 2014
... Therefore, most of the recent nutrient removal studies have focused on the removal of phosphorus. In the environment, the usual forms of phosphorus found in solutions include orthophosphate, polyphosphate and organic phosphate (Shin et al., 2007;Akbal and Kuleyin 2010; *Corresponding author. E-mail: sdehghan2010@gmail.com. ...
As well known, eutrophication is one of the main problems encountered in surface water. This phenomenon is caused by the excess phosphate level in the effluent of wastewater treatment plant. Thus, to control of eutrophication, removal of phosphorus is required. The aim of this study was to determine the efficiency of electrocoagulation (EC) process to phosphorus removal from the synthetic wastewater. This study was an experimental work which has been carried out by steel electrodes at constant current density of 1.15 mA/cm 2 on synthetic wastewater. The effect of reaction time and initial phosphate concentration is also studied. The results showed that the maximum removal efficiency of 98.72 and 100% was achieved for adenosine-5'-monophosphate (AMP) and sodium hexamethaphosphate (SHMP), respectively. In conclusion, electrochemical process is very efficient for removal of phosphate from the synthetic wastewater.
... In EC process, coagulants are generated by dissolving aluminum (which yields Al 31 [10]) or iron (which yields Fe 21 [11,12]) from the anode. Simultaneously, hydroxyl ions and hydrogen gas are released from the cathode by the reduction of water molecules [10,13]. The occurrence of electrochemical reactions leads to the production of various ferrous, ferric, and Al(III) hydroxide and polyhydroxide species depending on the pH of the aqueous medium [10]. ...
The removal of Reactive red 43, as a model pollutant, and some organic dyes with different structures by electrocoagulation process was investigated using iron (EC-Fe) and aluminum (EC-Al) anodes to explain dyes removal mechanism differences in EC-Fe and EC-Al processes. First, the effects of current density, electrolysis time and pH on the removal of Reactive Red 43were studied. The maximum removal efficiency (RE) was obtained in relatively acidic medium (pH = 4.25) in the first 12 minutes of EC-Al. While, in EC-Fe, a significant lag time between the starting of the process and initiation of considerable dye removal was observed. The color RE was supplemented with determining the RE of chemical oxygen demand. The COD values were determined for decolorization of solution containing 50 mg/L of RR43 and after 24 min of processes when the applied current density to monopolar batch electrochemical reactor was 25 A/m2. The COD removal efficiencies for the mentioned conditions were 73.92% and 97.12% for EC-Al and EC-Fe processes, respectively. The kinetics studies were carried out for both EC-Al and EC-Fe processes. In the similar operational conditions, the removal of basic dyes was not considerable by EC-Al. However, the RE of anionic dyes was improved with the addition of the number of sulfonate substituted groups. The maximum RE of all cationic and anionic dyes (RE > 90%) was achieved using EC-Fe. The enmeshment of dyes on iron oxide/hydroxide precipitates and charge neutralization were the main removal mechanisms in EC-Fe and EC-Al processes, respectively. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 547–556, 2013
... In this context, electrochemical technique is considered to be a powerful means for the treatment of dyeing wastewater. Indeed, electrochemical method has been successfully tested and it has certain significant advantages such as simple equipment, easy operation and lower operating cost [9][10][11][12]. The process requires significantly less equipment than conventional biological treatment processes [13,14]. ...
... A number of specific dyestuffs have been investigated, e.g. orange II [9], acid orange 7 [10], acid yellow 36 and 23 [11,12], reactive yellow 84 [13], acid red 14 [14], reactive black 5 [15], direct red 23 [16], acid red 2 [17], acid green 50 [18], crystal violet [19], acid blue 29, reactive red 2, acid red 97, reactive blue 4 [20], reactive blue 140 [21], reactive blue 29 [22], reactive orange 84 [23] and real wastewater containing dyes [24][25][26][27]. In both batch and continuous flow reactors, the decolorization efficiency has been found to depend on the initial pH, the dye concentration, and the applied current density. ...
This study presents an investigation of electrochemical variables and an application of the optimal parameters in operating a continuous upflow electrocoagulation reactor in removing dye. Direct red 23, which is azo-based, was used as a representative of direct dyes. First, a batch mode was employed to optimize the design parameters: electrode type, electrode distance, current density and electrocoagulation time. The optimal parameters were found to be iron anode, distance between electrodes of 8 mm and current density of 30 A·m-2 with contact time of 5 min. The performance of the continuous upflow reactor with these parameters was satisfactory, with >95% color removal and energy consumption in the order of 0.6-0.7 kWh·m-3.
Bu çalışmada, Gidya kullanılarak Everzol Yellow 3RS boyar maddesinin adsorpsiyon prosesi ile giderimi araştırılmıştır. Adsorpsiyon sürecine pH’ın (3–11), temas süresinin (5–300 dakika), adsorban dozunun (2–16 g/L), başlangıç konsantrasyonunun (10-50 mg/L) ve sıcaklığın (25-60°C) etkisi incelenmiştir. Adsorpsiyon prosesinde 10 g/L adsorbent dozu, orijinal pH değeri, 90 dakika temas süresi, 10 mg/L boyar madde konsantrasyonu ve ortam sıcaklığı optimum maksimum giderim veriminin (%90.96) sağlandığı koşullar olarak belirlenmiştir. Gidya üzerindeki adsorpsiyon sürecinin mekanizmasını anlamak için kinetik ve denge modelleri uygulanmıştır. Kinetik ve izoterm deneylerinden elde edilen sonuçlara göre, Everzol Yellow 3RS boyar maddesinin Gidya üzerine adsorpsiyonu için adsorpsiyon kinetiği ikinci derece reaksiyon modeli modeli ile adsorpsiyon dengesi ise Freundlich izoterm modeli ile iyi bir şekilde tanımlanmıştır. Bu, hız sınırlayıcı adımın difüzyondan ziyade kemisorpsiyon olabileceği ve hem film difüzyonu hem de parçacık içi difüzyon süreçlerinin kayda değer olduğu anlamına gelmektedir. Ayrıca, adsorpsiyon mekanizmasının düzgün bir dağılım göstermediğini ve tek bir katmanla sınırlı olmadığını göstermiştir. Sonuç olarak, Gidya’nın potansiyel bir adsorbent olarak boyar madde gideriminde kullanılabilir olduğu görülmüştür.
Dyes represent major environmental concerns since their presence in aqueous effluents posed a threat to the ecological system. This work is focused on developing a sustainable photo‐Fenton strategy for efficient Levafix Blue oxidation. Nanostructured magnetite as the precursor of the oxidation technique has been synthesized via a simple co‐precipitation technique. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) were applied to characterize the samples. The experimental dye removal data revealed that almost complete dye removal (99.9%) was attained at pH 3.0 using 800 and 40 mg/L of H2O2 and magnetite reagents, respectively within 30‐min of irradiation time. The process follows the first‐order reaction model with endothermic and non‐spontaneous oxidation reaction in nature with a low activation energy barrier of14.29 kJ/mol. Finally, the experimental data reveals that magnetite could be easily recovered and recycled up to six treatment cycles with a removal efficiency of 71% confirms the process sustainability.
Electrocoagulation (EC) process was investigated for the removal of acid green 20 (AG 20) dye from aqueous solutions with a batch-stirred bi-polar system using aluminum (Al) and iron (Fe) electrodes. Many operating parameters were investigated to achieve the best removal conditions to work. The removal percent (% Re) of AG 20 under optimum conditions was 96.38% and 94.81% and the energy consumption was 28.84 and 31.02 (kWh kg-1 of the dye) for Fe and Al electrodes respectively. The results showed that increasing the applied current density enhanced the efficiency of removal, which in turn was affected by the type and quantity of added electrolyte. The % Re was adversely affected by pH and initial dye concentration and the optimum values were found to be pH 2 and 60 mg L-1 initial dye concentration with both metals. The computed energy consumption and total operating cost confirmed the economic dye removal by the EC technique. 0.5 g NaCl as supporting electrolyte proved to be the ideal quantity and type of supporting electrolyte. The process followed the first-order-rate equation and the thermodynamic studies provided a clear indication that the process is spontaneous and exothermic. Among other models, Freundlich isotherm fitted for Al while Fe followed the postulates of Temkin and Langmuir models. The variation of the electrode set showed that the efficiency of removal with Fe-Fe-Fe-Fe > hybrid > Al-Al-Al-Al. Finally, the correlation matrix and multiple regression analyses were studied and predictive equations were derived.
The study was useful for the treatment of Reactive red 223 (R223) and Coo-massie brilliant blue R250 (CBBR250) binary dye system by electrocoagulation process (EC). Moreover, the Al and Fe electrode were used as an anode and cathode, respectively. The response surface methodology (RSM) was adopted by utilizing central composite design to plan the experimental runs. The EC process was preceded under the effect of operating parameters including pH, NaCl, voltage and electrolysis time. The % color and COD removals were examined as response variables. The removal efficiency of RR223 and CBBR250 dye at optimum values was 89% and 94% and COD removal was 100%. The kinetic study was performed to determine the rate and rate constant. First and second order kinetic models were studied to figure out the exact mechanism of the dye removal using EC process. The estimated cost of the experimental design about 4.486 US$/dm 3 was also determined. This study showed that EC process is an economical way for the treatment of waste water .
Nowadays, treatment of chromium wastewater is very critical also important. The current study investigates the influence of electrocoagulation process parameters to reduce the chromium from wastewater. It has been observed that the initial pH (6), current density (25 mA/cm²), electrode distance (4 cm) and electrolysis time (30 min) were found to be optimum for a 97 % chromium removal. For the above said optimum condition, the electrical energy consumption was found to be 0.12 kWh/m³. A comparison between BBD and ANN shows high correlation coefficient values (R² (ANN) > 0.90 and R² (RSM) > 0.90). Results indicated that electrocoagulation process is a cheap and effective method to treat chromium wastewater.
In the present research work, it found that the Electrocoagulation Process (EC) could be effectively
utilized for the purification of tri-dye (Yellow 145, Reactive Red 195, and Blue 222) from wastewater of
the textile industry located in Karachi.
In the present research work, it found that the Electrocoagulation Process (EC) could be effectively utilized for the purification of tri-dye (Yellow 145, Reactive Red 195, and Blue 222) from wastewater of the textile industry located in Karachi. In order to purify the sample from the said dyes,the impacts of operational parameters namely pH, electrolysis time, amount of electrolyte and voltage were monitored on color and COD (chemical oxygen demand) removals potency using central composite design (CCD). As a result of this, the electrolysis time and amount of electrolyte showed a greater influence on color and COD removals than pH and voltage. The R² (regression coefficient) values of the effluent was observed from 87% to 98% by ANOVA (Analysis of Variance). Subsequently, the kinetic reaction was also determined in the discharge of industry. Simultaneously, The Fourier transform infrared (FTIR) analysis was performed to identify the presence of functional groups of the dyes contaminated in the sample. Afterwards, the inverse relation was observed between the concentration of NaCl and the specific electrical energy consumption (SEEC). Consequently, the sludge formation of tri-dyes was obtained from sample and then calculated. By this, the industrial effluent was filtered from three harmful dyes that can be very dangerous for human as well as aquatic life. Moreover, it is cost effective technique too because its operating cost is US$ 1.360/L. Hence, this method may be used as a purifier for effluents of textile industries.
The electrocoagulation (EC) process is an electrochemical means of introducing coagulants and removing suspended solids, colloidal material, and metals, as well as other dissolved solids from water and wastewaters. EC process has been successfully employed in removing pollutants, pesticides, and radionuclides. This process also removes harmful microorganisms. More often during EC operation, direct current is applied and electrode plates are sacrificed (dissolved into solution). The electrodissolution causes an increased metal concentration in the solution that finally precipitates as oxides and hydroxides. Due to the process design and low cost material, the EC process is widely accepted over other physicochemical processes. In this frame, this paper presents a general review of efficient EC technologies developed to remove organic and inorganic matter from wastewaters for environmental protection. Fundamentals and main applications of EC as well as progress of emerging EC treatments are reported. The influence of iron or aluminum anode on depollution of synthetic or real effluents is explained. The advantages of EC mechanisms with Al and Fe electrodes are extensively discussed. There are presented the advanced EC processes with in situ generation of hydroxyl radical. The importance of the operating parameters for efficient application of the EC process as well as the combination of this electrochemical technology with electroanalysis techniques and other technologies are commented.
Dyes are persistent compounds that are not easily biodegraded and are considered as carcinogenic. Electro-coagulation and electro-flotation method, due to its adaptability and compatibility with the environment, is regarded as one of the appropriate methods for the treatment of industrial wastewater containing dye. In this study in which stainless steel mesh electrodes with a horizontal arrangement are used, the most important parameters affecting the performance of the simultaneous system of electro-coagulation and electro-flotation, including electrodes area, of distance between electrodes, solution's electrical conductivity, type of electrolyte, and initial pH were examined. The effect of every one of these parameters in color removal efficiency of Acid Red 14 from artificial wastewater, energy consumption and anode was determined and their values were optimized. The area of the electrode equals 20.5 cm², the distance between the electrodes is 0.5 cm, electrical conductivity 3,600 μS/cm, and initial pH 7 were selected as the optimum values, and dye removal efficiency of 99% with initial concentration of 150 mg/L and electric current density 40 mA/cm² (0.8 A) were obtained under optimum conditions and within 20 minutes. The advantages of this method are low energy and material consumption, and low sludge production.
Reactive dyes represent the most important class of dyes used in the colouration of cellulose fibre based textiles. Due to a limited degree of dyestuff fixation and competitive hydrolysis of the reactive anchor group in the alkaline dyebath substantial amounts of hydrolysed dyestuff are released at the end of the dyeing process. Assuming a rather high degree of dyestuff fixation with 90%, still 20,000 tonnes of hydrolysed dyestuff are released per year thus forming heavily coloured effluents. A number of techniques have been proposed to treat such waste water streams, e.g. coagulation, precipitation, absorption, chemical destruction and electrochemical decolourisation. A clean alternative presented in this article utilises the direct cathodic reduction of the azo-chromophores, which up to now has been proposed for treatment of concentrated dyestuff solutions. A distinct problem arises from the much low concentrations of reactive dyes in exhausted dyebaths, which has been investigated in this study. As technically relevant representatives three bifunctional reactive dyes Levafix Amber CA, Levafix Fast Red CA and Levafix Blue CA, which can form a trichromy have been studied. The cathodic electron transfer has been analysed with cyclic voltammetry on a hanging mercury drop electrode. Potentiometric titration with Fe(II)-triethanolamine complexes was used to determine the reducing equivalents for complete dyestuff reduction. A multi-cathode electrolyser was applied to study the cathodic dyestuff decolourisation in batch experiments as basis for extrapolation to full scale operation. Successful reductive decolourisation could be obtained for all three investigated dyes. In case of Leavfix Amber CA the original colour recovered some hours after the experiment had been terminated due to air oxidation of the reduced dyestuff. Due to the low dyestuff concentrations present in the dyebath current efficiency was determined with 2.8–8.0% and energy consumption was estimated with of 5.6 kWh/m³ of wastewater to achieve 80% dyestuff decolourisation. The results demonstrate the potential of the technique however also indicate that careful selection of all dyes with regard to their electrochemical behaviour is required for successful implementation of this technology.
The conventional coagulation technique of textile wastewater treatments is plagued with the issue of low removal rate of pollutants and generation of a large quantity of sludge. Recently, electrocoagulation (EC) technique gained immense attention due to its efficiency. The technique involves dissolution of the sacrificial anodes to provide an active metal hydroxide as a strong coagulant that destabilizes and amasses particles and then removes them by precipitation or adsorption. EC process is influenced by operating parameters such as applied current density, electrodes material and configuration, type of electrical connection, pH and conductivity of the solution, and mixing state. Consequently, this work reviewed the major and minor reactions of EC process with operational parameters, design of EC cell, mass transfer studies and modeling, and industrial wastewater applications. The work also includes comparison of EC technique with conventional coagulation and combinations with other techniques. Special emphasis is on removal of pollutants from textile wastewater. Further, the electrical energy supplies and cost analysis are also discussed. Even though several publications have covered EC process recently, no review work has treated the systematic process design and how to minimize the effect of passivation layer deposited on the surface of the electrodes. EC process with rotating electrodes has been recommended to reduce this phenomenon. The effect of electrodes geometry is considered to enhance the conductivity of the cell and reduce energy consumption. The studies of ionic mass transfer were not implemented before special by limiting current method during the EC process. Moreover, no aforementioned studies used computational fluid dynamics modeling to present the mass transfer inside the EC reactor.
One can describe industries involving dye treatment as the essentials (food, beverage, and textile) simply since they involve application to entities that are used for necessity. Dye wastewater is generated from the intense application within its industry. However, it is more common to find research on the treatment and application of dyes within the textile industry, as it has been highlighted and targeted by federal regulations. Some of the more harmful components from dye wastewater include the presence of biochemical oxygen demand (BOD), chemical oxygen demand (COD), and color, to name a few. Direct discharge from the plant can cause potential harm toward a water body, impacting the lives of human health and the environment. The purpose of this chapter is to provide a survey of various treatment methods and review the literature that has been applied for the purpose of treating wastewater produced by the textile dye industry. In addition, the text will discuss some of the important preceding topics prior to treatment applications such as legislation, and definition and classification of dyes. The aim of this chapter is to be both comprehensive and concise describing some of the major components that are heavily integrated within the dyeing industry.
Decolorization of wastewater of industries which consume dye is an environmental priority. Electrocoagulation and electroflotation methods are appropriate for treatment of these wastewaters. This study investigates the effect of four parameters including electrical conductivity, current density, initial dye concentration, and initial pH on the performance of a simultaneous electrocoagulation/electroflotation system for removal of Acid Red 14. The optimum values of these parameters were determined based on the amount of electrical energy and aluminum consumption and the best performance of coagulation and bubble generation. The optimum condition revealed to be electrical conductivity = 1,600 μS/cm, current density = 60 mA/cm2, initial dye concentration = 185 mg/L and initial pH = 7. After less than 180 min of electrolysis, 90% dye removal was achieved with a specific energy consumption = 102 kWh/kg dyeremoved, anode dissolution = 2.09 kg Al/kg dyeremoved and sludge TSS = 15,050 mg/L. LC-UV-Mass analyses were conducted on samples of raw and treated wastewater. Results found that intermediate compounds formed from the breaking of the dye molecules. The advantages of this method are a low material and energy consumption. The amount of produced sludge was low; consequently sludge disposal and management costs would be reduced. This method should be used cautiously for treatment of textile wastewater due to the formation of intermediate compounds.
Due to the possibility of contamination of surface and groundwater in the vicinity of industries which consume dye, decolorization of wastewaters of these industries is an environmental priority. Electro-coagulation and electro-floatation methods are appropriate for treatment of wastewaters containing dye. In a conductive solution, when electricity is supplied to the electrodes, one of which is the positive anode and the other one is the negative cathode, the coagulant is dissolved in-situ from the anode with simultaneous formation of hydroxide ions and hydrogen gas generation at the cathode. In this study, four parameters of electrode surface area, inter-electrode distance, electrical conductivity and current density were examined. Optimum values of these parameters are determined based on amount of electrical energy and aluminium consumption and best performance of coagulation and bubble generation. With initial dye concentration of 65 mg/L after 90 min of electrolysis, 90% dye removal was achieved under optimum condition of electrode surface area=24.86 cm2, inter-electrode distance=1 cm, electrical conductivity=1600 µS/cm and current density=60 mA/cm2 with specific energy consumption=130 kWh/kg dye removed, anode dissolution=2.615 kg Al/kg dye removed and sludge TSS=15050 mg/L. The advantages of this method are the low material and energy consumption. The amount of produced sludge is low and as a consequence sludge disposal and management costs will be reduced.
This paper reports multistep optimization studies on electrochemical (EC) treatment of textile wastewater containing three dyes namely basic orange 30, basic violet 16 and basic green 4 using an aluminum electrode. Chemical oxygen demand (COD) and color removal efficiencies were maximized in a batch EC experimental reactor. In first step, Plackett-Burman (PB) design was used to sort most effective factors amongst the various factors namely current density (j), time (t), electrode gap (g), temperature (T), initial pH (pHo) and NaCl salt concentration (m) that affected the removal efficiency. In the next step, steepest accent/descent method and Box- Behnken (BB) design methods were utilized to evaluate the optimum electrochemical conditions. In BB design, three operational parameters, namely j: 117.64- 196.07 A/m2; t: 150-210 min and pHo: 3.5-5.5 were taken as input parameter whereas COD removal (Y1) and color removal (Y2) were taken as responses of the system. At the optimum operating conditions of j = 185.30 A/m2, t = 190 min and pHo 5, more than 70.5% COD and 98.2% color removal efficiencies were observed. Field emission scanning electron microscopy of aluminum electrodes, scum and sludge has been carried out to understand the EC mechanism.
In this work electrocoagulation for phosphorus removal from wastewater using iron electrodes as cathode and anode was investigated. In this study several parameters were considered namely: distance between electrodes, ammonia and COD with the addition NaCl equal 0.5 g. It was found short gap was better for phosphorus removal and effect of ammonia and COD enhance performance of phosphorus from 89.2 to 90.1 and 91 respectively for a current the 0.8 A at 55 min.
Herein we report a study on the changes in zeta potential during the electrochemical (EC) treatment of basic green 4 (BG) dye solutions. BG is a basic acrylic dye with a triphenylmethane group. It is extensively used in the textile and other industries. This study was conducted in a batch electrochemical reactor using a sacrificial aluminum anode. Zeta potentials were measured with changes in operating variables such as current density (j), initial pH (pH0), and initial dye concentration (C0). The process performance was analyzed in terms of the chemical oxygen demand (COD), total organic carbon (TOC) and decolorization efficiency along with important cost-related parameters such as electrode and energy consumption. At the optimum conditions, 82.4% COD, 63.5% TOC and 99.4% color removal efficiencies were observed, when C0 = 100 mg L−1, the treatment time was 45 min, with j = 117.64 A m−2 and the initial pH0 = 6.2. The respective electrode and energy consumptions at the optimum conditions were 0.16 kg Al per kg COD removed and 2.48 kW h per kg COD removed. The magnitude of the zeta potential gave an indication regarding the potential stability of the colloidal suspensions of BG dye and aluminum flocs present in the solution over the pH range of 3.2-12.2. It was found that the removal of the cationic dye was maximum when the zeta potential was least negative and that the removal was due to adsorption on neutral aluminum hydroxide. Finally, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), pore size distribution and thermogravimetric analysis (TGA) techniques were used to characterize the solid residues obtained during the EC treatment of aqueous solutions with and without BG dye.
The present study investigates the electrochemical (EC) treatment of actual dye bearing effluent (DBE) with different combinations of aluminum (Al) and stainless steel (SS) electrodes as anode and cathode. Effects of the current density (j) and pH with different anode–cathode combinations (Al–Al, Al–SS, SS–SS, and SS–Al) were studied. The change in zeta (ζ) potential with current density at different times, and the change in colloid particle diameters at different pH, gave information regarding the potential stability of the colloidal suspension. In addition, specific energy consumption and current efficiency have also been calculated. Maximum color, COD, TOC, and turbidity removal efficiencies were found to be 99.90%, 82.50%, 68.8%, and 98.8%, respectively, at j = 117.64 A/m2 and pH 8.5 with the SS–SS electrode combination. Solid residue obtained during EC treatment of DBE was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, thermogravimetric analysis, and pore distribution analysis to propose reutilization of the sludge.
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The objective of this study is to establish some relations between the physical properties of the sludge (i.e., specific resistance to filtration, capillary suction time …) and membrane fouling in a submerged membrane bioreactor, for high solid retention time (SRT) conditions. The analysis of the membrane performances, carried out with an analysis of the depollution performances and of the activated sludge physical properties, is proposed in an experimental membrane bioreactor (MBR) unit working with complete biomass retention. It is first confirmed that high-SRT conditions involve a high degree of organic degradation, with low sludge yield. A continuous increase of the viscosity can be observed during time but the sludge dewatering behaviour can be considered as constant, despite the total suspended solids (TSS) increase. No direct correlation is established between the transmembrane pressure (TMP) evolution and the conventional parameters used to describe sludge dewaterability but it can be assumed that the sludge filtration is not possible when TSS and viscosity reach “critical” values. Soluble microbial substances and mean floc size diameter evolutions cannot explain the decrease of membrane permeability, although these compounds may enhance fouling. The characterisation of the bulk suspension seems to not provide enough informations to anticipate the evolution of the membrane fouling and some complementary methodologies, allowing the characterisation of the environment close to the membrane, have to be developed.
Electrocoagulation (EC) is an efficient method for textile wastewater treatment. Researches are mainly focused on the technical performance of this process, while its economic aspect has been usually neglected. This paper deals with a simplified operating cost analysis for the treatment of a textile wastewater by EC using iron and aluminium electrode materials. The effects of various parameters such as wastewater conductivity and pH, current density and operating time, on the operating cost have been discussed for two electrode materials, separately.
The removal of chemical oxygen demand (COD), color and suspended solid (SS) from olive oil mill wastewater (OMWW) was experimentally investigated by using electro-coagulation (EC). Aluminum and iron were used in the reactor simultaneously as materials for electrodes. The reactor voltage was 12 V, current density (CD) was changing between 10 and 40 mA cm−2, pH was taken equal to 4, 6, 7, and 9 units, and duration varied in the limits of 2–30 min. Under the 30-min retention time, 52% COD was removed by the aluminum anode and 42% was removed by the iron anode. CD efficiency versus the percent of COD removal was examined at the 10-min retention time for pH 6.2±0.2. It appeared that with the CD increase, the percent of COD removal was increasing as well. The color removal yield was examined as the result of using different retention times, current densities, and iron and aluminum as materials for anodes. CD values in the range of 10–40 mA cm−2 were tested at the 10-min retention time each one; color removal was 90–97% by this. In this study the EC process was examined with the aim of determining the highest rate of SS removal from the OMWW as well.
Although electrocoagulation is an evolving technology that is being effectively applied today for wastewater treatment, the paucity of scientific understanding of the complex chemical and physical processes involved is limiting future design and hindering progress. The objective of this review through a survey of the literature is to bring the chemistry and physical processes involved into perspective and to focus attention on those areas critically needing research.
The aim of this paper was to investigate the feasibility of the removal of phosphate from aqueous solution by electro-coagulation (EC). The current density (CD) between 2.5 and 10 mA cm(-2) and duration in the limits of 5-20 min were tried for different concentrations. In order to determine optimal operating conditions, the EC process used for the phosphate removal was examined in dependence with the CD, initial concentrations and time. The results of the experimental batch processing showed high effectiveness of the EC method in removing phosphate from aqueous solutions.
Electrocoagulation (EC) is one of the most effective techniques to remove color and organic pollutants from wastewater, which reduces the sludge generation. In this paper, electrocoagulation has been used for the removal of color from solutions containing C. I. Basic Red 46 (BR46) and C. I. Basic Blue 3 (BB3). These dyes are used in the wool and blanket factories for fiber dyeing. The effect of operational parameters such as current density, initial pH of the solution, time of electrolysis, initial dye concentration and solution conductivity were studied in an attempt to reach higher removal efficiency. The findings in this study shows that an increase in the current density up to 60-80 A m(-2) enhanced the color removal efficiency, the electrolysis time was 5 min and the range of pH was determined between 5.5 and 8.5 for two mentioned dye solutions. It was found that for, the initial concentration of dye in solutions should not be higher than 80 mg l(-1) in order to achieve a high color removal percentage. The optimum conductivity was found to be 8 mS cm(-1), which was adjusted using proper amount of NaCl with the dye concentration of 50 mg l(-1). Electrical energy consumption in the above conditions for the decolorization of the dye solutions containing BR46 and BB3 were 4.70 kWh(kgdye removed)(-1) and 7.57 kWh(kgdye removed)(-1), respectively. Also, during the EC process under the optimized conditions, the COD decreased by more than 75% and 99% in dye solutions containing BB3 and BR46, respectively.
Treatment of chemical mechanical polishing (CMP) wastewater was investigated. The CMP wastewater, as obtained from surface treatment of photovoltaic wafers, was characterized by high suspended solids, high nephelometric turbidity unit (NTU), chemical oxygen demand (COD) and green color. This study determines the feasibility of CMP wastewater treatment by the electrocoagulation process. The COD concentration of the CMP wastewater was found in the range of 700 mg/l which is below the discharge standards. The analysis of the wastewater before and after electrocoagulation shows that the electrochemical process was a total barrier for the metal species, color and a significant reduction in the concentration of the fluoride and sulfate ions.
This study investigates the influence of variables on the decolorization efficiency of a solution containing Tartrazine (a synthetic yellow azo dye) by D.C. electrocoagulation (EC). The efficiency of different electrode connections and materials (iron, aluminium) for color removal is compared. Current density, time of electrolysis, interelectrode distance, supporting electrolyte concentration and pH of the solution were the variables that mostly influenced the color removal. Initially, a simple electrochemical cell was prepared with an anode and a cathode, then the effect of each variable was studied separately using aqueous Tartrazine in a batch mode. For a solution of 40mgl−1 Tartrazine+400mgl−1 NaCl with chemical oxygen demand (COD) of approximately 30mgl−1, almost 100% color and 90% COD were removed, when the pH was about 5.78, time of electrolysis was approximately 6min, current density was approximately 120Am−2 and interelectrode distance was 1.5cm. In the second series of experiment, the efficiency of EC cells with monopolar electrodes in series and parallel connections and an EC cell with bipolar electrodes was compared with that of a simple electrochemical cell. The results revealed that EC cell with monopolar electrodes in series connection was more effective where aluminium electrodes were used as sacrificial and iron was used as anode and cathode. Electrocoagulation with Fe/Al (anode/cathode) was more effective for the treatment process than Fe/Fe electrode pair.
The monomer–dimer equilibria of Cibacron Blue F3GA (CB) and five other dyes (Levafix Brilliant Blue EB, Reactive Scarlet 017, Methyl Orange, Basic Blue 3 and Chicago Blue Sky) have been investigated in water and in the presence of KH2PO4. Aggregation of CB has been also examined in the presence of NaH2PO4, LiCl and KCl. When a new iterative approach, based on non-linear least-square (NLLSQ) fitting procedure was applied, it was found that the dimerization constants depend on the extension of organic molecules and the number of sulphonic groups. In the case of CB, cations had a greater effect on the equilibrium than anions. Analysis of the calculated spectra for monomer and dimer of Basic Blue 3 after deconvolution allowed us to specify the geometry of the dimer.
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.
The electrocoagulation process was developed to overcome the drawbacks of conventional wastewater treatment technologies. This process is very effective in removing organic pollutants including dyestuff wastewater and allows for the reduction of sludge generation. The purposes of this study were to investigate the effects of the operating parameters, such as current density, electrode number, electrolyte concentration, electrode gap, dyestuff concentration, pH of solution and inlet flow rate, on decolorization by continuous electrocoagulation. The dye removal efficiencies and reaction rate constants from the curves following the first-order relationship of electrocoagulation were calculated. In addition, from the points of power consumption, the effects of the operating parameters were also searched. Finally, the behaviors of decolorization according to dyestuff types, i.e., disperse dye and reactive dye, were also examined.
Boron compounds are used in the variety of products manufacturing and are introduced to the environment in the form of waste. Here the feasibility of the boron removal from wastewater by electrocoagulation (EC) is studied. Aluminum and iron were simultaneously used in the reactor as materials for cathode and anode. The results show that the EC process for boron removal strongly depends on the current density, initial concentrations, and time. The process is examined under varying indices in order to determine optimal operating conditions. It is important to note the EC application needs no chemical reagents and makes the boron-containing wastewater treatment easy for regulation and automation.
The performance of an electrocoagulation system with iron electrodes for Cr(VI) removal from model wastewaters in laboratory scale was studied systematically. Several parameters – such as initial metal concentration (10–50 mg/l Cr), charge loading, and applied current – and their influence on the electrocoagulation process were investigated. Cr concentration decreased only slightly by coagulation time at high currents (1.0–3.0 A), whereas at low currents (0.05–0.1 A), 10 mg/l Cr was removed completely from the solution after 45 min. Initial concentrations from 10 to 50 mg/l Cr did not influence the removal rates at low currents, whereas higher initial concentrations caused higher removal rates at high currents. At all investigated currents, the Cr(VI) concentration was always only a little lower than the Crtotal concentration and the Fe2+ concentration in solution was always below 0.1 mg/l. The study gave indications on two different removal mechanisms of Cr(VI) with iron electrodes at high and low currents. We propose that at high currents Cr(VI) was reduced directly at the cathode and precipitated afterwards as Cr(OH)3. The Cr removal depended on initial concentration and the removal rate (μmol/As) was independent from the inserted current. At low currents the Cr(VI) removal was proposed to work by reduction by Fe2+. Under these conditions, iron was quantitatively dissolved as Fe2+ from the electrodes according to Faraday's law and the dissolved amounts were two orders of magnitude higher compared to the iron dissolution at high currents. The removal process at low currents was much more efficient and seemed to be applicable for the removal of Cr(VI) from industrial wastewaters.
An attempt has been made to remove chemical oxygen demand (COD) from olive mill wastewaters (OMW) as well as oil-grease and turbidity in the presence of H2O2 and polialuminum chloride (PAC), as a coagulant-aid by an electrochemical method using either iron or aluminum as sacrificial electrodes. The effects of current density, electrode material and polarization, amount of hydrogen peroxide using as an oxidizing agent and addition of coagulant-aid, on percent removal and energy consumption have been investigated. According to the results, Fe was determined more effective than Al as an electrode. The removal efficiency of COD was in the range of 62–86% whereas oil-grease and turbidity removal was 100% at the current density range of 20–75 mA cm−2 depending on the concentrations of H2O2 and coagulant aid. It is obtained that the electrocoagulation in the absence of coagulant aid and oxidant is not too efficient for the treatment of this type of wastewater. The polarity of the electrodes played an important role in the treatment of OMW.
This investigation assessed the decolorization efficiency of Procion Red MX-5B in electrocoagulation (EC), UV/TiO2 and ozone-related systems. The effectiveness of energy input was also determined. The decolorization rate constants of these EC, UV/TiO2 and ozone-related systems fitted pseudo-first-order kinetics and the values were in the order O3 (24 W) > O3 (16 W) > O3 (16 W)/EC (8 W) > UV/TiO2/O3 (8 W)/EC (8 W) > O3 (10 W) > UV/O3 (8 W)/EC (8 W) > UV/O3 (8 W) > O3 (8 W) > UV/TiO2/O3 (8 W) > O3 (8 W)/EC (8 W) > O3 (4 W)/EC (4 W) > UV/TiO2/EC (8 W) > UV/TiO2 > UV/EC (8 W) > EC (8 W). The decolorization rate constants increased with the total power input. Additionally, the decolorization efficiency could be promoted by combining UV with O3, UV with EC, EC with UV/TiO2 and EC with UV/O3. This study reveals that combining EC with UV/TiO2 or UV/O3 can trigger a Fenton or Fenton-like reaction, which accelerates the rate of decolorization. The solution pH of O3, UV/O3 and UV/TiO2 systems declined during decolorization; in contrast, the pH increased to 7.4 in the UV/EC system. The effective energy consumption constant did not increase with the total power input and reached maximum at a total power input of approximately 10–16 W.
The effect of surfactant as the organic component of the simulated wastewater on aluminium as electrode material was studied. The characterisation of electrode material referred to various solutions (low sodium chloride concentration, sodium sulphate and anionic, cationic and non-ionic surfactants) and conditions of pH. The overall anodic and cathodic processes were studied by voltammetric techniques in potentiostatic and galvanostatic variants. The scan rate ranged between 0.02–200 V/s and 0.0001–0.01 A/s, respectively. The electrode processes could be stimulated or inhibited depending on scan rate, history of the electrode, pH and surfactant type. The change of the anodic inhibition or activation was interpreted by the character of superficial oxide film and partially defilming process. Such aspects correlated to some extent with the electrode activity in electrocoagulation. The simulated water treatment was carried out in an electrocoagulation cell in galvanostatic conditions. The efficiencies of treatment ranged between 40 and 60% as chemical oxygen demand (COD) removal.
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.
The effective performance of electrocoagulation (EC) technique in the treatment of olive mill wastewater (OMW) has been investigated using sacrificial aluminium electrodes. The optimum working pH was found to be in the range 4–6, allowing OMW to be treated directly without pH adjustment. In addition, it is found that an increase in the current enhanced the speed of the treatment significantly. However, simultaneous increase of electrode and energy consumption was observed. The optimum current density allowing the quickest treatment with a low cost was found to be 75 mA cm−2. Therefore, a current density of 75 mA cm−2 was selected as an optimum that allows fast and low cost treatment.Application of electrocoagulation procedure permitted high removal efficiencies of pollutants with both fresh and stored olive mill wastewater. The process produces a removal capacity of 76% of COD, 91% of polyphenols and 95% of dark colour, just after 25 min. The electrode consumption was found to be 2.11 kg m−3 of treated OMW. The results show that electrocoagulation could be considered as an effective alternative solution for the treatment of OMW or may be combined with a classical biological process to achieve a high quality effluent water.
Treatment of chemical mechanical polishing (CMP) wastewater is investigated. The CMP wastewater, as obtained from a large semiconductor manufacturer, was characterized by high suspended solids (SS) content, high Nephelometric turbidity unit (NTU), chemical oxygen demand (COD) concentration up to 500 mg/l, copper concentration over 100 mg/l and a milky color. This study was to explore the feasibility of treating the CMP wastewater by electrocoagulation with an aim of simultaneously lowering the wastewater turbidity, and copper and COD concentrations. Experiments were conducted to analyze the characteristics of the CMP wastewater and to evaluate the effects of electrocoagulation time, type of electrode pair and electrolyte dosage on the system performances. The fine suspended oxide particles were found to have an average size of 100 nm with narrow particle size distribution between 68 and 120 nm. The test results revealed that Al/Fe (anode/cathode) was a good electrode pair in terms of overall performances. Electrocoagulation with Al/Fe electrode pair was able to achieve 99% copper removal and 96.5% turbidity reduction in less than 100 min. The COD removal obtained in the treatment was better than 75%, with an effluent COD below 100 mg/l. The wastewater quality exceeded the direct discharge standard and the effluent can be considered for reuse.
The decolorization of C.I. Acid Red 14 (AR14) azo dye by electrocoagulation (EC) process was studied in a batch reactor. Response surface methodology (RSM) was applied to evaluate the simple and combined effects of the three main independent parameters, current density, time of electrolysis and initial pH of the dye solution on the color removal efficiency and optimising the operating conditions of the treatment process. A 23 full factorial central composite face centred (CCF) experimental design was employed. Analysis of variance (ANOVA) showed a high coefficient of determination value (R2 = 0.928) and satisfactory prediction second-order regression model was derived. Maximum color removal efficiency was predicted and experimentally validated. The optimum current density, time of electrolysis and initial pH of the dye solution were found to be 102 A m−2, 4.47 min and 7.27, respectively. Under optimal value of process parameters, high removal (>91%) was obtained for Acid Red 14. This study clearly showed that response surface methodology was one of the suitable methods to optimize the operating conditions and maximize the dye removal. Graphical response surface and contour plots were used to locate the optimum point.
The present work deals with removal of trivalent chromium (Cr3+) from aqueous solutions in a batch stirred electrocoagulator with mild steel electrode pair. Effects of operating time, stirrer rpm, current density, initial pH, initial concentration of Cr3+ and supportive electrolyte (NaCl) concentration have been investigated. Removal of Cr3+ during electrocoagulation (EC) is due to combined effect of chemical precipitation, co-precipitation, sweep coagulation and adsorption. At higher current density and solution pH, remarkable removal of Cr3+ was observed. Single stage of electrocoagulation could reduce Cr3+ concentration from 1000 mg/l to the discharge limit of 2 mg/l. Three different regimes of Cr3+ removal rate (g/m3 min) viz. (i) sluggish, (ii) high and (iii) decline rate regimes are observed with progress of EC. Current efficiency of about 100% with respect to Fe dissolution from electrodes was observed. NaCl not only increases the conductivity of the solution but also has impact on electrode passivation and removal of Cr3+. High resolution X-ray diffraction study of sludge revealed its amorphous nature. Electrocoagulated sludge is highly rich in Cr3+ and the maximum value of the mass ratio, Cr3+/Fe in sludge was found to vary from 3.5 to 4.0. Around 4% additional removal was noticed after 60 min of EC with same duration of post-EC contact. This is attributed to chemical precipitation and co-precipitation effects.
This research attempted to find the optimum condition for color and total COD reduction in wastewater from the pulp and paper mill industry by using electrocoagulation techniques in batch and continuous modes. Six pieces of iron plates constructed in parallel configurations were used as electrodes. The effect of key parameters including the type of polyelectrolyte, current density, initial pH of the wastewater, and the circulating flow rate of wastewater in the reactor were investigated. The results indicated that the polyelectrolyte had no effect on pollutant removal. At optimum conditions, greater than 97% of color and 77% of total COD were effectively removed with a total operating cost of approximately 0.29 USD/m3 wastewater. First order rate kinetics best explained the reduction of color and total COD concentration, the model fitting the actual data very well. For the continuous mode, the treatment process reached the steady state condition within 2.15 h and the efficiency of color and total COD reduction was greater than 91% and 77%, respectively. The properties of wastewater including color, total COD, BOD5, TSS, TDS, pH and iron ions content were in the range of the acceptable values of current Thai Government standards.
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.
Treatment of spent final rinse water of zinc phosphating from an automotive assembly plant was investigated in an electrochemical cell equipped with aluminum or iron plate electrodes in a batch mode by electrocoagulation (EC). Effects of the process variables such as pH, current density, electrode material and operating time were explored with respect to phosphate and zinc removal efficiencies, electrical energy and electrode consumptions. The optimum operating conditions for removal of phosphate and zinc were current density of 60.0 A/m(2), pH 5.0 and operating time of 25.0 min with Al electrode and current density of 60.0 A/m(2), pH 3.0 and operating time of 15.0 min with Fe electrode, respectively. The highest phosphate and zinc removal efficiencies at optimum conditions were 97.7% and 97.8% for Fe electrode, and 99.8% and 96.7% for Al electrode. The electrode consumptions increased from 0.01 to 0.35 kg electrode/m(3) for Al electrode and from 0.20 to 0.62 kg electrode/m(3) for Fe electrode with increasing current density from 10.0 to 100.0 A/m(2). The energy consumptions were 0.18-11.29 kWh/m(3) for Al electrode and 0.24-8.47 kWh/m(3) for Fe electrode in the same current density range. Removal efficiencies of phosphate and zinc were found to decrease when flow rate was increased from 50 to 400 mL/min in continuous mode of operation. The morphology and elements present in the sludge was also characterized by using SEM and EDX.
Batch electrocoagulation experiments were carried out to evaluate the removal of sulfate and COD from petroleum refinery wastewater using three types of electrodes: aluminum, stainless steel, and iron. The effects of current density, electrode arrangement, electrolysis time, initial pH, and temperature were investigated for two wastewater samples with different concentrations of COD and sulfate. The experimental results indicated that the utilization of aluminum, as anode and cathode, was by far the most efficient arrangement in the reduction of both the contaminants. The treatment process was found to be largely affected by the current density and the initial composition of the wastewater. Although electrocoagulation was found to be most effective at 25 degrees C and a pH of 8, the influence of these two parameters on the removal rate was not significant. The results demonstrated the technical feasibility of electrocoagulation as a possible and reliable technique for the pretreatment of heavily contaminated petroleum refinery wastewater.
The present study provides an electrocoagulation process for the remediation of phosphate-contaminated water using aluminium, aluminium alloy and mild steel as the anodes and stainless steel as the cathode. The various parameters like effect of anode materials, effect of pH, concentration of phosphate, current density, temperature and co-existing ions, and so forth, and the adsorption capacity was evaluated using both Freundlich and Langmuir isotherm models. The adsorption of phosphate preferably fitting the Langmuir adsorption isotherm suggests monolayer coverage of adsorbed molecules. The results showed that the maximum removal efficiency of 99% was achieved with aluminium alloy anode at a current density of 0.2 A dm(-2), at a pH of 7.0. The adsorption process follows second-order kinetics.
The removal efficiency of COD in the treatment of simulated laundry wastewater using electrocoagulation/electroflotation technology is described. The experimental results showed that the removal efficiency was better, reaching to about 62%, when applying ultrasound to the electrocoagulation cell. The solution pH approached neutrality in all experimental runs. The optimal removal efficiency of COD was obtained by using the applied voltage of 5V when considering the energy efficiency and the acceptable removal efficiency simultaneously. The Cl(-) concentration of less than 2500ppm had a positive effect on the removal efficiency. The performance of the monopolar connection of electrodes was better than that of the bipolar connection in this work. In addition, the removal efficiency of using Al electrodes was higher in comparison with using Fe electrodes in the study. The highest COD removal amount per joule was found to be 999mgdm(-3)kWh(-1) while using two Al electrodes, although the removal efficiency increased with the number of Al plates.
Treatment of textile wastewaters by electrocoagulation using iron and of aluminum electrode materials has been investigated in this paper. The effects of relevant wastewater characteristics such as conductivity and pH, and important process variables such as current density and operating time on the chemical oxygen demand (COD) and turbidity removal efficiencies have been explored. Furthermore, the electrode and energy consumptions for each electrode have been calculated. The results show that iron is superior to aluminum as sacrificial electrode material, from COD removal efficiency and energy consumption points.
In the present study electrocoagulation (EC) has been evaluated as a treatment technology for arsenite [As(III)] and arsenate [As(V)] removal from water. Laboratory scale experiments were conducted with three electrode materials namely, iron, aluminum and titanium to assess their efficiency. Arsenic removal obtained was highest with iron electrodes. EC was able to bring down aqueous phase arsenic concentration to less than 10 microgl(-1) with iron electrodes. Current density was varied from 0.65 to 1.53 mAcm(-2) and it was observed that higher current density achieved rapid arsenic removal. Experimental results at different current densities indicated that arsenic removal was normalized with respect to total charge passed and therefore charge density has been used to compare the results. Effect of pH on arsenic removal was not significant in the pH range 6-8. Comparative evaluation of As(III) and As(V) removal by chemical coagulation (with ferric chloride) and electrocoagulation has been done. The comparison revealed that EC has better removal efficiency for As(III), whereas As(V) removal by both processes was nearly same. The removal mechanism of As(III) by EC seems to be oxidation of As(III) to As(V) and subsequent removal by adsorption/complexation with metal hydroxides generated in the process.
This study was performed to investigate the variables that influence the efficiency of decolorization of a solution containing an azo dye (Acid Red 14) by electrocoagulation (EC) in order to compare the efficiency of different electrode connections for color removal. Current density, time of electrolysis, interelectrode distance, and pH of the solution were the variables that most influenced color removal. Initially, a simple electrochemical cell was prepared with an anode and a cathode. Then the effect of each variable was studied separately using synthetic wastewater in a batch mode. The efficiency of the method tested was determined by measurement of color removal and reduction of Chemical Oxygen Demand (COD). For dye solutions with COD of approximately 30 ppm and dye concentrations less than 150 ppm, high color removal (93%) was obtained when the pH ranged from 6 to 9, time of electrolysis was approximately 4 min, current density was approximately 80 A/m2, the temperature was approximately 300 K, and interelectrode distance was 1 cm. During the EC process under these conditions, the COD decreased by more than 85%. In the second series of experiment, the efficiency of EC cells with monopolar electrodes in series and parallel connections and an EC cell with bipolar electrodes were compared with results using a simple electrochemical cell. The experimental results showed that an EC cell with several electrodes was more effective than a simple electrochemical cell in color removal. The results also showed that an EC cell with monopolar electrodes had a higher color removal efficiency than an EC cell with bipolar electrodes. Furthermore, within an EC cell, the series connection of the monopolar electrodes was more effective for the treatment process than the parallel connection in color removal.
The performance of electrocoagulation, with aluminium sacrificial anode, in the treatment of metal ions (Cu2+, Zn2+ and Cr(VI)) containing wastewater, has been investigated. Several working parameters, such as pH, current density and metal ion concentrations were studied in an attempt to achieve a higher removal capacity. Results obtained with synthetic wastewater revealed that the most effective removal capacities of studied metals could be achieved when the pH was kept between 4 and 8. In addition, the increase of current density, in the range 0.8-4.8 A dm(-2), enhanced the treatment rate without affecting the charge loading, required to reduce metal ion concentrations under the admissible legal levels. The removal rates of copper and zinc were found to be five times quicker than chromium because of a difference in the removal mechanisms. The process was successfully applied to the treatment of an electroplating wastewater where an effective reduction of (Cu2+, Zn2+ and Cr(VI)) concentrations under legal limits was obtained, just after 20 min. The electrode and electricity consumptions were found to be 1 g l(-1) and 32 A h l(-1), respectively. The method was found to be highly efficient and relatively fast compared to conventional existing techniques.
The effect of the molar ratio of hydroxide and fluoride ions to Al(III) ions (gamma(OH) and gamma(F)) on coagulation and electrocoagulation (EC) was studied to solve the problem of the over addition of acid or base. The efficiency of defluoridation was approximately 100% when the sum of gamma(OH) and gamma(F) (gamma(OH+F)) was close to 3. This finding reveals that the fluoride ions and the hydroxide ions can co-precipitate with Al(III) ions and the formula of the precipitate is Al(n)F(m)(OH)(3n-m). However, when gamma(OH) was less than 2.4, the defluoridation efficiency, given that gamma(OH+F)=3, dropped as gamma(OH) fell, because the amount of aluminum polymer formed dropped. The efficiency of defluoridation of EC exceeded that of coagulation for equal gamma(OH) and gamma(OH+F), when gamma(OH+F)>3, proving the existence of an electrocondensation effect.
Boron removal from wastewaters by electrocoagulation using aluminum electrode material was investigated in this paper. Several working parameters, such as pH, current density, boron concentration and type and concentration of supporting electrolyte were studied in an attempt to achieve a higher removal capacity. The experiments were carried out by keeping the pH of solution constant and optimum pH of solution was determined 8.0 for the aluminum electrode. Although energy consumption increased with decreasing boron concentration, which conductivity of these solutions were low, boron removal efficiency was higher at 100 mg/L than that of 1000 mg/L. Current density was an important parameter affecting removal efficiency. Boron removal efficiency and energy consumption increased with increasing current density from 1.2 to 6.0 mA/cm2. The types of different supporting electrolyte were experimented in order to investigate to this parameter effect on boron removal. The highest boron removal efficiency, 97%, was found by CaCl2. Added CaCl2 increased more the conductivity of solution according to other supporting electrolytes, but decreased energy consumption. The results showed to have a high effectiveness of the electrocoagulation method in removing boron from aqueous solutions.
The paper presents the study of electrocoagulation (EC) of aqueous dye solutions of two different industrial dyes in a batch stirred cell. Experiments were carried out with 200 mg/l individual concentration of methylene blue (MB) and eosin yellowish (EY) in presence of NaCl as electrolyte. Effect of operating time and current density on the decolorization of dye solutions, reduction of chemical oxygen demand (COD) and variation in conductivity, pH during treatment has been studied. Small difference between color diminution and COD reduction has been found with the progress of treatment. First-order rate equation for dye removal has been developed from the experimental results. Sludge formation during EC and problems associated with this solid waste generation and disposal has been assessed. Energy consumption in KWh/m(3) with reduction of COD (kg) during treatment has been reported. Electric power consumption of 1.5 KWh reduces 0.21 and 0.11 kg COD from 0.24 and 0.14 kg of initial COD for MB and EY, respectively, starting from 200 mg/l dye concentration.
The decolorization of the levafix orange textile dye in aqueous solution by electrocoagulation using aluminum sacrificial anode has been investigated. The process performance is analyzed in terms of decolorization efficiency and the important cost-related parameters such as electrode and energy consumptions, as a function of initial pH, conductivity, current density, initial dye concentration and electrolysis time. The present study proves the effectiveness of electrochemical treatment for the textile dye solution. 95% decolorization efficiency may be obtained at suitable operating conditions such as; current density 100 A/m(2), operating time 12 min and initial pH 6.4. The corresponding electrode and energy consumptions during the electrolysis were found to be 1.8 kg Al/kg dye and 35 k Wh/kg dye.
The removal of COD and oil-grease from dairy wastewater was experimentally investigated using direct current (DC) electrocoagulation (EC). In the EC of dairy wastewater, the effects of initial pH, electrolysis time, initial concentration of COD, conductivity and current density were examined. The COD and oil-grease in the aqueous phase were effectively removed when iron was used as sacrificial anode. The optimum operating range for each operating variable was experimentally determined. The batch experimental results revealed that COD and oil-grease in aqueous phase was effectively removed. The overall COD and oil-grease removal efficiencies reached 98 and 99%, respectively. The optimum current density, pH and electrolysis time for 18,300 mg COD/L and 4570 mg oil-grease/L were 0.6 mA/cm2, 7 and 1 min, respectively. Mean energy consumption was 0.003 kWh/kg of COD.
Removal of Cr(3+) from aqueous solutions by electrocoagulation (EC) with multiple electrodes was studied with both bipolar and monopolar configurations. The influence of chloride ions, pH, initial Cr(3+) concentration and cell current on removal performance was investigated in a batch stirred cell. It was noted that, the enhancement of solubility of Cr(OH)(3) and co-precipitated [Cr, Fe](OH)(3) in presence of chloride ions results in reduction of removal efficiency. Removal of Cr(3+) improved at higher pH due to combined effect of precipitation, co-precipitation as solid solution like species, adsorption, cathodic reduction and sweep coagulation. The maximum Cr(3+) removal per unit charge loading was found to be increasing with increase in initial Cr(3+) concentration. The cell current efficiency was less than that predicted from Faraday's law of electrolysis for both configurations. The operating cost was estimated from the power cost and cost of electrode material. The former was 40% and the later was 43% higher for bipolar configuration compared to monopolar configuration for achieving final chromium discharge limit of 2.0mg/l.
This study aims to investigate the treatment of paper mill effluents using electrocoagulation. Removal of lignin, phenol, chemical oxygen demand (COD) and biological oxygen demand (BOD) from paper mill effluents was investigated at various current intensities by using different electrodes (Al and Fe) and at various electrolysis times (1.0, 2.5, 5.0 and 7.5min). It was observed that the experiments carried out at 12V, an electrolysis time of 2min and a current intensity of 77.13mA were sufficient for the removal of these pollutants with each electrode. The removal capacities of the process using an Al electrode were 80% of lignin, 98% of phenol, 70% of BOD, and 75% of COD after 7.5min. Using an Fe electrode the removal capacities were 92%, 93%, 80% and 55%, respectively. In addition, it was found that removal of lignin, phenol, BOD and COD increased with increasing current intensity. In the experiments carried out at different current intensities, higher removal can be explained through a decrease in intra-resistance of solution and consequently an increase at the transfer speed of organic species to electrodes. It was also found that Al electrode performs higher efficiency than Fe electrode except for COD removal. However, the time required for removal of BOD was more than that of COD. The results suggest that electrocoagulation could be considered as an effective alternative to paper mill effluents treatment.
This study investigates the evaluation of specific electrical energy consumption (SEEC) and the influence of operating parameters on the color removal efficiency of a dye solution containing C.I. Acid Yellow 23 by electrocoagulation process. Firstly, the operational parameters including current density, initial dye concentration, initial pH and time of electrolysis were optimized. Then the effects of the conductivity, the interelectrode distance and the area of cross-section of the electrodes on specific electrical energy consumption (SEEC) were studied under the optimum conditions. Our results indicated that for a solution of 50mg/l C.I. Acid Yellow 23, almost 98% color and 69% chemical oxygen demand (COD) were removed, when the pH was about 6, the time of electrolysis was 5min and the current density was approximately 112.5A/m(2). In addition, the results of our study revealed that when the conductivity and area of cross-section of the electrodes increased and interelectrode distance decreased, the cell voltage and specific electrical energy consumption would be decreased.
In the laboratory-scale experiments, treatment of baker's yeast production wastewater has been investigated by electrocoagulation (EC) using a batch reactor. Effects of the process variables such as pH, electrode material (Fe and Al), current density, and operating time are investigated in terms of removal efficiencies of chemical oxygen demand (COD), total organic carbon (TOC), turbidity, and operating cost, respectively. The maximum removal efficiencies of COD, TOC and turbidity under optimal operating conditions, i.e., pH 6.5 for Al electrode and pH 7 for Fe electrode, current density of 70 A/m2 and operating time of 50 min were 71, 53 and 90% for Al electrode and 69, 52 and 56% for Fe electrode, respectively. Al electrode gave 4.4 times higher removal efficiency of turbidity than Fe electrode due to interference from color of dissolved iron. The operating costs for Al and Fe electrodes in terms of /kg COD were 1.54 and 0.82, 0.51 and 0.27, respectively.
Treatment of tannery wastewater by electrocoagulation with low cell current (< or = 1A) and soluble electrodes (mild steel electrodes and aluminum electrodes) was studied. Compared with aluminum electrodes, mild steel electrodes were more effective for the removal of sulfide, with a removal efficiency of over 90%. But during the treatment process, black color precipitate typical to iron(II) sulfides was produced. While aluminum electrodes were effective to eliminate the colority of the effluent, the removal efficiency of sulfide was lower than 12%. The mechanisms of the removal of chemical oxygen demand, ammonia, total organic carbon, sulfide and colority with the two soluble electrodes (mild steel and aluminum electrodes) were discussed in detail. In order to exert the predominance of diffenent types of electrodes, the tannery wastewater was treated using mild steel electrodes first followed by the filter and finally by the aluminum electrodes, the elimination rates of chemical oxygen demand, ammonia, total organic carbon, sulfide and colority were 68.0%, 43.1%, 55.1%, 96.7% and 84.3%, respectively, with the initial concentrations 2413.1 mg/L, 223.4 mg/L, 1000.4 mg/L, 112.3 mg/L and 256 dilution times, respectively. The absorbance spectra and energy consumption during electrocoagulation process were also discussed.
Removal of Cr(VI) from model wastewaters by electrocoagu-lation with Fe electrodes, Separation and Purifica-tion Technology
- I Heidmann
- W Calmano
Heidmann, I., & Calmano, W. (2007). Removal of Cr(VI) from model wastewaters by electrocoagu-lation with Fe electrodes, Separation and Purifica-tion Technology, 61, 15–21.
Olive oil mill wastewater treatment by means of electro-coagulation, Separation and Pu-rification Technology
- Inan
- H Dimoglo
- A Ek
- H Karpuzcu
_ Inan, H., Dimoglo, A., S ims ek, H., & Karpuzcu, M. (2004). Olive oil mill wastewater treatment by means of electro-coagulation, Separation and Pu-rification Technology, 36, 23–31.