Article

Mineralization of C.I. Reactive Blue 19 by Ozonation Combined with Sonolysis: Performance Optimization and Degradation Mechanism

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Abstract

Mineralization of an anthraquinone dye, C.I. Reactive Blue 19 (RB19), by single ozonation, single sonolysis, and ozonation combined with sonolysis (O3/US) was carried out in a laboratory-scale experiment. O3/US treatment rendered a more effective result than the other two methods. The effect of several operational parameters, including initial dye concentration, pH, ozone dose, and ultrasonic energy density, on the reduction of total organic carbon (TOC) was also investigated. The concentrations of related anions (maleic acid, oxalic acid, acetic acid, formic acid, nitrite ion, nitrate ion and sulfate ion) and the ammonium ion during mineralization were detected by ion chromatography (IC) and the ammonia–Nessler's reagent colormetric method, respectively. Other carbon based intermediates (3,6-dinitrosocyclohexa-1,4-diene, aniline, phenol, benzo-1,4-quinoe, phthalic acid, butene diacid, oxalic acid, and acetic acid) were detected by gas chromatography/mass spectrometry (GC/MS). Based on the results of these analyses, we propose a possible degradation pathway of RB19 during the O3/US process.

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... According to their chemical structure, dyes can be classified into azoic-which constitute the majority group-, anthraquinonic, nitro, indigoid, diphenyl and triphenyl methane, phtalocyanines and polymethines [1]. Anthraquinone dyes are characterized by their high resistance to biodegradation, due to their fused aromatic structures [2][3][4]. In addition, they could be toxic and cause mutagenic effects on organisms exposed to their effects [5,6]. ...
... In particular, several studies have successfully carried out the degradation of RB19 through ozonation processes, most of them focusing on the efficiency and kinetics of discoloration [31,32] and on the effect of operational parameters [33,34] although there exist large discrepancies about the reaction conditions required to achieve discoloration and/or mineralization of the effluents [4,27,33,34]. The studies performed by He [3] and Fanchiang and Tseng [4] are especially significant contributions referred to the identification of intermediaries and the proposal of reaction mechanism for the ozonation of RB19 solutions. In our previous report [20] the effects of operational parameters were investigated and a degradation pathway was proposed for the discoloration and mineralization of RB19 using ozone and ozone/UV. ...
... The experimental time required to reach 50% conversion of RB19 and Total Organic Carbon ( t RB19 1∕2 and t TOC 1∕2 , respectively) were used as response for the experimental design. According to published literature [15] and previous studies [20], the applied ranges of process parameters were: pH [3][4][5][6][7][8][9][10] and O g,i 3 [50-100] gm −3 NTP, and for all cases the dye initial concentration was 250 mg L −1 . The same procedure was employed to each of UV radiation intensities: 0 W and 40 W, giving a total of 24 experiments. ...
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This work reports the degradation of Reactive Blue 19 (RB19) dye using ozone and ozone/UV. The effects of operational parameters such as pH, ozone concentration and UV radiation were examined. A two factor with three levels factorial design was carried out and the interaction between variables was studied. Response surface methodology was applied in order to optimize ozone concentration, pH and UV radiation in terms of the half life time required for discoloration and/or mineralization of the solution. Equations of color and TOC half-life time with respect to operational conditions were determined. Contour plots and a desirability function were used to find the local points of optimization. Optimized reaction conditions were established as pH 8.26, UV radiation of 40 W and ozone concentration of 50 g Nm−3. A specific experiment was carried out under the optimal conditions where RB19 half life time was 1.59 min and TOC half life time was 30.98 min, confirming the agreement between model and experimental results. The obtained results confirm ozonation as a promising alternative for treatment of wastewater with a high content of recalcitrant reactive dyes.
... These dyes contaminated water might be harmful for both aquatic and human life, producing hazardous mutagenic or carcinogenic effect in human being [1,2]. The discharge of dyes into water, depressed photosynthesis as well as respiration processes of aquatic system [3]. Hence, the treatment of water containing these hazardous pollutants is a major issue for environmental chemist [4][5][6][7]. ...
... Among them, Fenton process (Fe 2+ /H 2 O 2 ) is the commonly used for degradation of dyes and other organic pollutants. Because, it has many advantages: (1) it involves the breakdown of H 2 O 2 into environmental friendly species such as O 2 and H 2 O, (2) it is a non-toxic process [20], (3) and it is simple, it can be employed at STP and (4) and yield high efficiency [21]. Our group has already reported AY-17 dye removal by Fe 2+ /H 2 O 2 and UV/Fe 2+ /H 2 O 2 system [22,23]. ...
... The optimum concentration of H 2 O 2 , Fe 3+ , and AY 17 were determined for achieving high degradation efficiency. The effects of pH, temperature and various anions (CO 3 2− , HCO 3 − , Cl − and SO 4 2− ) on the efficiency of dye degradation were investigated. Kinetic study of dye degradation reaction was also carried out. ...
... Reactive dyes are photolytically/chemically stable and either not biodegradable under aerobic conditions, or they degrade slowly via conventional biological processes, producing vividly coloured treated effluents (Guimaraes et al. 2012). They are highly soluble in water and contain environmentally problematic and toxic compounds (He et al. 2008;Liu et al. 2010;Guimaraes et al. 2012;Mahne et al. 2012). Phenol is a serious organic water pollutant because it is toxic at low concentrations (Busca et al. 2008). ...
... These experiments were performed to check whether subjection of ozone to catalytic/photocatalytic decomposition influenced the degradation kinetics of pollutants in the following experiments. The ultrafast disappearance of RB19 is most probably the consequence of the fast reaction of O 3 with the dye chromophores (He et al. 2008;Panda and Mathews 2014), especially in a more acidic environment ). This is correlated with instant ozone consumption, followed by gradual increase of ozone concentration during subsequent stages of the process, when stable intermediates resistant to ozone attack are formed. ...
... This was proof that O 3 oxidation reactions result in stable degradation products (e.g. quinones, phenols, maleic acid, oxalic acid, formic acid, acetic acid) (He et al. 2008;Marques et al. 2010), and the decomposition process stops. It was demonstrated that oxalic acid is the major RB19 degradation product (He et al. 2008) which is, similarly as phenol, very slowly mineralized by ozonation alone (Chen et al. 2014). ...
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A compact reactor for photocatalytic oxidation and photocatalytic ozonation water treatment was developed and evaluated by using four model pollutants. Additionally, combinations of pollutants were evaluated. Specially produced Al2O3 porous reticulated monolith foams served as TiO2 carriers, offering a high surface area support. UV lamps were placed in the interior to achieve reduced dimensions of the reactor (12 cm in diameter × 20 cm in height). Despite its small size, the overall photocatalytic cleaning capacity was substantial. It was evaluated by measuring the degradation of LAS + PBIS and RB19 as representatives of surfactants and textile dyes, respectively. These contaminants are commonly found in household grey wastewater with phenol as a trace contaminant. Three different commercial photocatalysts and one mixture of photocatalysts (P25, P90, PC500 and P25 + PC500) were introduced in the sol-gel processing and immobilized on foamed Al2O3 monoliths. RB19 and phenol were easily degradable, while LAS and PBIS were more resistant. The experiments were conducted at neutral-acidic pH because alkaline pH negatively influences both photocatalyic ozonation (PCOZ) and photocatalysis. The synergistic effect of PCOZ was generally much more expressed in mineralization reactions. Total organic carbon TOC half lives were in the range of between 13 and 43 min in the case of individual pollutants in double-deionized water. However, for the mixed pollutants in tap water, the TOC half-life only increased to 53 min with the most efficient catalyst (P90). In comparison to photocatalysis, the PCOZ process is more suitable for treating wastewater with a high loading of organic pollutants due to its higher cleaning capacity. Therefore, PCOZ may prove more effective in industrial applications.
... Например, в сочетании с электрокоа-гуляцией позволяет предотвращать осаждение загрязнений на поверхности электродов [7]. Комбинированное применение ультразвуковой обработки и озона исследовано в работах [9][10][11]. Изучено влияние мощности излучателя и времени обработки на деструкцию ПАВ [9]. ...
Article
Представлены результаты исследования эффективности очистки модельных и реальных сточных вод красильно-отделочных производств комбинированием ультразвуковой обработки и озонирования. Изучено влияние времени обработки, концентрации озона в газовой смеси на эффективность очистки. Эффективность очистки оценивали по оптической плотности и ХПК. В результате исследований было показано повышение эффективности очистки сточной воды до 12% при комбинировании флотации озоновоздушной смесью вместо воздуха с ультразвуковой обработкой. Данный эффект может быть связан, в первую очередь, с диспергированием пузырьков озоновоздушной смеси, что приводит к увеличению их суммарной поверхности и, соответственно, к увеличению кинетики массообмена – растворения озона. Ключевые слова: крашение тканей, сточная вода, озон, флотация, краситель The results of studying the efficiency of purification of model and real wastewater from dyeing and finishing works by combining ultrasonic treatment and ozonation are presented. The effect of the treatment time, ozone concentration in the gas mixture on the purification efficiency has been studied. The purification efficiency was evaluated by optical density and COD. As a result of the study up to 12% increase in the efficiency of wastewater treatment was shown while combining flotation with ozone-air mixture instead of air with ultrasonic treatment. This effect can be associated, first of all, with the dispersion of ozone-air mixture bubbles that results in an increase in the surface area, and, accordingly, in an increase in the kinetics of mass transfer – ozone dissolution. Key words: fabric dyeing, wastewater, ozone, flotation, dye.
... When US is introduced into the ozonation system, the ultrasonic irradiation could enhance the mass transfer, dispersion, and solubility of ozone [148]. By means of the pyrolytic decomposition of ozone inside cavities at the collapse, oxidizing free radicals are produced [147,149,150]. Additionally, the synergy of the combination of US with ozone is based on operating parameters, such as the frequency of ultrasound and dissolved ozone concentration [151]. ...
Article
Trace organic contaminants (TrOCs) have been increasingly found in the aquatic environment and their potential health risk on human and wildlife has attracted more attention. Ozone-based advanced oxidation processes (AOPs) are a key technology for the removal of TrOCs from water and wastewater. This review provides an overview of current research and technology development regarding the application of ozone-based AOPs for TrOCs abatement. Performance of ozonation as a stand-alone process, as well as combined processes, including O3/H2O2, O3/UV, O3/catalysts, O3/plasma and O3/filtration for the removal of TrOCs in various types of (waste)water is discussed. Furthermore, this review also analyses the main mechanisms of oxidation by-products generation and compares and discusses the energy consumption during the application of ozone-based AOPs.
... Various conventional methods for dealing with textile waste such as biological oxidation, physicalchemical treatment and adsorption have been carried out. However, these methods are less effective because most dyes are soluble in water, have complex structures and are resistant to chemical and biological degradation [2]. In addition, they have a high operational cost and toxic by-products are formed during the process. ...
Article
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Synthetic dyes are one of the most dangerous components of textile wastewater. Waste that contains various organic compounds, especially synthetic dyes, causes a high Chemical Oxygen Demand (COD) values. Remazol blue is a reactive dye that is widely used for the textile dyeing process. Therefore, water pollution occurs when the dye waste produced from textile activities is discharged into water bodies without prior treatment. In this study, innovation in waste treatment technology was applied in the Dielectric Barrier Discharge (DBD) plasma reactor. DBD are non-thermal plasma reactors designed to degrade organic and inorganic compounds in wastewater through oxidation process. This is carried out by active species, such as ozone (O3), hydrogen peroxide (H2O2) and hydroxyl radical (•OH), which are formed in the reactor. The study aims to evaluate the performance of non-thermal DBD plasma reactor in treating wastewater containing one of the textile dyes, namely remazol blue. The results showed that the percentage of degradation achieved was 98.43% within a process time of 120 minutes with a final concentration of 0.75mg/L. Furthermore, it showed that optimum conditions were obtained at pH value of 4, air flow rate of 2.5L/min, liquid flow rate of 50mL/min and a primary Neon sign transformer (NST) voltage of 19kV.
... Among them, advanced oxidation processes (AOPs) based on photocatalyst have been widely utilized to produce nonselective hydroxyl radicals with remarkable potential for pollutant decomposition (Ribeiro et al., 2015;Aziz et al., 2018). AOPs can be applied individually or in combination with other treatment methods to achieve higher degradation efficiency in lower reaction time (He et al., 2008;Jafari et al., 2017). AOPs based on conventional photocatalysts suffer from low stability, poor light absorption, and a high recombination rate of photo-generated carriers (Dashtian et al., 2018(Dashtian et al., , 2019(Dashtian et al., , 2020. ...
Article
In this study, a facile four-step hydrothermal method was utilized to deposit a core-shell structure on UiO-66(Zr/Ti) nanoflake (NFs) as a visible-light-driven photocatalyst. The core was magnetic Fe3O4 which served as a charge carrier coated with WO3 shell. The as-prepared photocatalyst was characterized by XRD, VSM, BET, FTIR, FE-SEM, UV–Vis-DRS, and PL techniques which proved successful deposition of Fe3O4@WO3 core/shell particle on UiO-66(Zr/Ti)-NFs. The obtained photocatalyst was subsequently applied for urea photo-oxidation. This magnetically recoverable photocatalyst exhibited superior activity due to its desirable band alignment, high stability, and generation of the photo-induced charge carriers, as well as providing a high surface area with low mass transfer resistance. Fe3O4 core acted as charge-carrier to transport the photogenerated charges of UiO-66(Zr/Ti)-NFs (electron-donor) to WO3 charge-collectors for effective photoconversion. The central composite design was applied to design the experiments matrix in which flow rate, pH, irradiation time, catalyst mass, and initial urea concentration were considered as operational factors. The optimized condition was found by defining the desirability function. 90% degradation percentage was achieved at 550 mL/min solution flowrate, pH = 7, 120 min irradiation time, 0.22 g UiO-66(Zr)-NFs-Fe3O4@WO3, and 40 mg/L of the initial concentration of urea with the desirability value of 0.89. Such a superior photocatalytic activity of UiO-66-Fe3O4@WO3 can be ascribed to the reclamation of Fe3O4 as a low bandgap carrier, which accelerated the conveyance of electrons and followed surpassing charge separation. Our present findings open a new strategy to produce a wide range of core-shell heterogeneous catalysts to be applied in photoreactors scale-up.
... However, additional enhancement in ultrasonic power up to 400 W did not lead to improvement of dye degradation efficiency. It could be deduced that at high ultrasonic power, a portion of ultrasonic power would be consumed and converted to heat, because of the existence of scattering effect [29]. Therefore, US power 200 W was a suitable condition for US/PMS/CuFe 2 O 4 process. ...
Article
Sunset yellow (SY) dye removal from aqueous solution was assessed by ultrasound/peroxymonosulfate/CuFe2O4 nanoparticles. CuFe2O4 nanoparticles were synthesized and their properties were well determined by several advanced techniques. The effects of pH, catalyst dosage, peroxymonosulfate (PMS) concentration, and ultrasound (US) intensity were investigated on the decolorization. The best results (95.8% removal) were observed at pH=7, CuFe2O4= 25 mg/L, PMS=1.5 mM, US=200 W and 30 min. Nitrite and bicarbonate ions demonstrated high inhibition effect on the decolorization. PMS depicted high activity in the presence of CuFe2O4 compared to S2O 2-8 and H2O2. Around 40% reduction in the decolorization was observed in reusability experiments. Sulfate and hydroxyl radicals were the major species of SY degradation based on quenching experiments. A mineralization of 50% was obtained only in 30min reaction time. This process can be effective for the destruction of organic dyes in colored wastewater.
... These dyes are colored compounds that contain functional groups, such as azo, phthalocyanine, anthraquinone, formazane, and oxazine as chromophore [4,12]. Azo dyes constitute about 60% of reactive dyes and play a significant role in dyestuff chemistry, followed by anthraquinone dyes [4,13]. There are two key components in the azo dye molecules, namely the chromophores, and the auxochromes. ...
Article
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This article focuses on developing a methodology which can be used to estimate the concentration of dyestuff released from textiles during domestic laundering, so that further studies involving decolorization of the wastewater from domestic washing machine can be conducted in an attempt to develop eco-friendly domestic washing processes. Due to the complexity of the problem, an approach was adopted so that, as an initial step, synthetic red and blue reactive dye solutions were prepared as representative wastewater solutions using Reactive Red 195 and Reactive Blue 19 dyestuffs for the estimation of dye concentration. This was followed by an experimental work consisting of washing tests involving the calculation of dye concentration in the wastewater obtained from domestic washing machine as well as tergotometer as a machine simulator. For this part of the work, dyed cotton plain jersey fabric samples were used to obtain wastewater solutions. All the dye solutions and the wastewater samples were measured with VIS spectrophotometer, and the maximum absorbance values were obtained at relevant wavelengths. Although the characteristics of absorbance spectra of synthetic and wastewater solutions were very different, the maximum absorbance values of both solutions overlapped at relevant wavelengths. The concentration of the dyestuff was calculated from the absorbance values measured at 540 and 592 nm for the red and blue, respectively. The statistical analysis of the data suggested that tergotometer can be used as a domestic washing machine simulator. Moreover, the regression analysis done for the dyestuff concentration under discussion revealed that the most significant factor was the washing step (main wash or rinsing) (89.5%) followed by color (red or blue) (3.4%) and washing device (washing machine or tergotometer) (1.5%).
... Some methods were used to remove of dyes from aqueous solutions. Various methods such as anaerobic/aerobic biological treatments [12], coagulation/flocculation [13], membrane filtration [14], oxidation [15], photo catalysis [16] and sonolysis [17] have been used for treatment of wastewater containing reactive dyes. However, these processes have disadvantages and limitations, such as high cost, generation of secondary pollutants and poor removal efficiency [18]. ...
Article
In this study, a multi-step experimental design of Response Surface Methodology (RSM) was applied to optimize the medium conditions for the maximum removal of Methylene Blue from aqueous solution by a novel fungi A. campestris as a biosorbent. In first step, the effect of factors (initial dye concentration, temperature, contact time, pH, agitation speed and adsorbent dosage) was obtained using Plackett Burman Design (PBD). Then Steepest Ascent (SAD) used to predict the optimum region of effective factors in the second step. Central Composite Design (CCD) was utilized to evaluate the optimum medium conditions of effective parameters for the removal of cationic dye on last step. RSM indicated that optimum conditions of initial dye concentration, agitation speed and medium temperature for maximum removal of MB (95%) were achieved as 130.90 mg L−1, 125 rpm and 41.87 °C, respectively. The activation energy (Ea) was determined as 149.1, -178.6, 154.5 and 382.3 kJ/mol for 20, 50, 100 and 200 mgL-1 respectively. The characterization of adsorption process was confirmed by Scanning Electron Microscope (SEM) and Fourier Transform Infrared 2 Spectroscopy (FTIR). Adsorption isotherm was used to describe the adsorption equilibrium studies at different temperature99999s. Langmuir isotherm shows better fit than Freundlich and Temkin isotherms. Thermodynamic parameters like the enthalpy 15 kJ/mol (ΔHo), entropy 66.59 J/molK (ΔSo) and Gibbs free energy -4.47 kJ/mol (ΔGo) were evaluated and also, ΔGo shows a negative values indicating that the adsorption process was spontaneous and endothermic in nature. The results show that a multi-step statistical optimization designs is successful applied to experiments and novel and endemic biomass of Agaricus Campestris is an appropriate biosorbent and has a specific affinity for removal of Methylene Blue at under optimal conditions.
... This result is consistent with other studies (ADAMS & GORG, 2002; TURHAN et al., 2012; TURHAN & OZTURKCAN, 2013) and occurs because increasing ozone concentration in air bubbles enhances the driving force for the transfer of ozone from the gas phase into the dye solution. Consequently, there is more ozone dissolved in the solution, and the rate of dye oxidation is higher (SEVIMLI & SARIKAYARAGHUVANSHI et al., 2005;HE et al., 2008;TURHAN et al., 2012).It has been reported that the RB19 is only partially oxidized by ozone, without complete mineralization(CHU & MA, 2000; FANCHIANG & TSENG, 2009a; 2009b). However, according to Fanchiang and Tseng ...
Article
Full-text available
Dyes highly reduce sunlight penetration into the stream, and consequently affect photosynthesis and oxygen transfer into water bodies. An experimental and analytical modelling approach to Reactive Blue 19 (RB19) removal using ozone was carried out. For this purpose, factors and mass ratio analyses were assessed based on batch assays experiments. Removal efficiency increased from 64 to 94% when the dosage increased from 38.4 to 153.6 mg O3.L-1. Results showed that RB19 is more efficiently removed when initial pH is 7. The rate of RB19 removal decreased as the initial dye concentration increased. Kinetic studies showed that the ozonation of RB19 was a pseudo first-order reaction with respect to the dye, and the apparent rate constant declined logarithmically with the initial dye concentration. Mass ratio studies showed that, for the empirical analysis, the power law equation was adequate to describe mass ratio over time and the analytical analysis suggests that the process is influenced by mass transfer in the liquid film as well as in the bulk fluid.
... 27 In addition, the possibility of the generation of more inorganic anions increased with the increasing in RB 19 dye concentration, so competing reaction between dye molecules and oxidation species. 28 ...
Article
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The study evaluated the degradation of antraquinone textile dye Reactive Blue 19, frequently used dye in the textile industry, by means of sulfate radicals. Sulfate radicals were generated by activation of peroxydisulfate with UV-C (254 nm) irradiation. The UV irradiation alone did not affect removal efficiency, while with addition of the oxidant removal efficiency was significantly improved. The degradation rates of textile dye increased at higher initial dosages of oxidant, while the opposite trend was observed in the case of increase in the initial dye concentration. Acidic conditions were more convenient for degradation of the dye then neutral and basic. Degradation of the textile dye was not affected by the presence of bicarbonate and chloride anions within the concentrations range from 1 up to 200 mmol∙L-1. The presence of carbonate showed suppressing effect on the removal efficiency especially at carbonate levels below 20 mmol∙L-1. However, at carbonate levels greater than 20 mmol∙L-1, dye removal efficiency increased. The use of methanol and tert-butyl alcohol as the scavengers revealed that both radicals, HO• and SO4•-, would be generated depending on initial pH value оf dye solution.
... The temperature was then increased up to 250°C at a rate of 10°C/minute and held for 2 min. The temperature of the source and injector were 70 and 270°C, respectively containing helium as a carrier gas with a flow rate of 1 mL/ minute and EI impact ionization of 70 eV (He et al., 2008). The GC-MS spectrum showed various peaks corresponding to respective retention time with proposed molecular weight. ...
Article
Synthesized iron-nickel (Fe–Ni) bimetallic nanoparticles (NPs) were utilized for the colour removal of C. I. Reactive Blue 21 (RB21) dye. NPs agglomeration was prevented using polyvinyl pyrrolidone (PVP) as a capping agent. The NPs were characterized by nanoparticle size analysis, TEM, XRD and EDX. The operational conditions like pH, NPs concentration and initial dye concentration for decolourization were optimized using mathematical modelling, and its kinetics were studied. Influence of the presence of alkali and salt on dye decolourization was also investigated. Decolourization products were analysed by using FTIR and GCMS analysis. 93.46% of dye decolourization was obtained and a reduction in COD, BOD values was achieved along with minimal sludge generation.
... However, the cost-effectiveness and environmentallyfriendly nature of this ACSS cathode-enabled EF system is significant. Additionally, we also observed that the cell voltage continuously decreased within 90 min, which indicates an increase in the conductivity of the electrolyte, possibly due to the formation of small molecules organic acids, such as formic acid and acetic acid [63]. ...
... Such change in color might be attributed to the oxidation and dimerization of phenylenediamine isomers by hydroxyl radicals (·OH) released during peroxide decomposition in the catalytic MnO 2 layer. 49 Figure S1 illustrates the possible mechanism for the oxidation of phenylenediamine isomers. As can be seen, isomers are oxidized by ·OH radicals via electron exchange and tend to polymerize to generate corresponding colors. ...
Article
Tubular micromotors composed of a hybrid single wall carbon nanotubes (SW)-Fe2O3 outer layer and powered by MnO2 catalyst are used for phenylenediamines isomers detection and discrimination. Catalytic decomposition of H2O2 as fuel results in the production of oxygen bubbles and hydroxyl radicals for phenylenediamines dimerization to produce colorful solutions in colorimetric assays. The combination of Fe2O3 nanoparticles along with the irregular SW backbone results in a rough catalytic layer for enhanced hydroxyl radical production rate and improved analytical sensitivity. Such self-propelled micromotors act as peroxidase-like mobile platforms that offer efficient phenylenediamines detection and discrimination in just 15 min. Factors influencing the colorimetric assay protocol, such as the navigation time and number of motors, have been investigated. Low limits of detections (5 and 6 µM) and quantification (17 and 20 µM) were obtained for o-phenylenediamine and p-phenylenediamine, respectively. The magnetic properties of the outer SW-Fe2O3 hybrid layer allow the reusability of the micromotors in the colorimetric assay. Such attractive performance holds considerable promise for its application in sensing systems in a myriad of environmental, industrial and health applications
... AOPs are based on the decomposition of pollutants via nonselec- tive hydroxyl radicals which simultaneously avoid secondary pollutants generation. Although, some AOPs methods such as fenton, photo- fenton, sonolysis, photocatalysis and ozonation are effective for degra- dation of many contaminants individually but hybrid systems including two or more individual AOPs can degrade pollutants with higher effi- ciency at least reaction time [8,9]. Combination of AOPs leads to development of non-toxic, eco-friendly, cost-effective and reproducible processes which permit safe and cleaner water media [10][11][12][13]. ...
Article
Cu/Fe3O4@SiO2 nanocomposites were synthesized and pre-specified by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-Ray (EDX) and band gap energy via diffuse reflectance spectroscopy (DRS) techniques which due to their reasonable band gap (2.58 eV) is suitable candidate for visible light-driven photocatalyst. The prepared nanocomposites were used as photocatalyst for degradation of tartrazine (TR) and methylene blue (MB) in binary mixture under an efficient sonophotocatalytic reactor. The effect of seven effective parameters including initial concentration of TR and MB (5–25 mg L⁻¹), photocatalyst dosage (0.10–0.50 mg L⁻¹), solution flow rate (40–120 mL min⁻¹), oxygen flow rate (0.20–0.60 L min⁻¹), pH (2.0–10) and irradiation time (5–25 min) was studied and optimized using central composite design. The maximum sonophotocatalytic degradation percentages at optimum condition were found to be 99.98% and 99.96% for TR and MB, respectively. The kinetic studies strongly confirmed ability of pseudo first order reaction based on the Langmuir-Hinshelwood model for explanation of data and experimental results confirmed that understudy process is rapid and effective approach.
... The characteristic absorption peaks of dye molecules greatly decease after exposure to UV light for 20 min or visible light for 30 min; this implies that the dye molecules in the residual dyeing liquors are almost completely photodegraded to smaller fragments. 60 As a result, the practical application of TiO 2 precursor in dyeing wastewater treatment process for color removal in dyeing liquors of reactive dyes is of great significance. ...
Article
In this article, the approach of dyeing polyamide (PA) fabric by using C.I. Reactive Blue 19 dye and simultaneously modifying it with titanium dioxide precursor under hydrothermal conditions is developed. The anthraquinone-based Reactive Blue 19 dye, which is more resistant to biodegradation owing to its fused aromatic structure compared to an azo-based one, is utilized as a model compound in this research to demonstrate the photodegradation effect of TiO2 on reactive dyes. It is shown that a layer of TiO2 nanoparticles is homogeneously coated on fiber surfaces and their particle sizes are smaller than those remaining in the residual dyeing liquors. The crystallinity and optical properties of the resultant PA fabrics are changed due to this hydrothermal dyeing process. In comparison with the dyed-only PA fabrics, the PA fabrics dyed and simultaneously modified with anatase TiO2 nanoparticles exhibit better color fastness against artificial light (xenon) while maintain similar grades of color fastness against washing with soap, wet scrubbing, dry cleaning as well as dry/wet rubbing. While changes in tensile strength, elongation and water absorbency of the resultant PA fabrics were not found, the addition of tetrabutyl titanate in the dyeing liquor is proved to facilitate the reaction of reactive dye with PA fabric and the resultant PA fabric shade. More interestingly, it is noticed that the residual dyeing liquor can be photodegraded after 50 mins of either UV or visible light irradiation, and the dyeing wastewater can thus be released in an eco-friendly manner to the environment.
... The extensive use of AR1 in textile industries results its presence in natural water resources (Anjaneyulu et al. 2005;Boyter 2007;Singh and Arora 2011). The degradation studies of a number of azo dyes by ZVINP, US and US-assisted advanced oxidation process are reported in the literature (Destaillats et al. 2000;Eren 2012;Ghodbane and Hamdaoui 2009;Gomathi Devi et al. 2011;He et al. 2008;Minero et al. 2005;Shu et al. 2007;Zhang et al. 2005). However, the individual or combined efficiency of these techniques against AR1 is not so far investigated. ...
Article
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The heterogeneous catalytic degradation of a model azo dye, acid red 1 (AR1), initiated by zero valent iron nanoparticles (ZVINP), and its synergic effect with ultrasound (US) have been investigated in the present study. The treatment of AR1 using ZVINP at pH 3 showed maximum efficiency in terms of colour removal (53.0%) and mineralization (48.5% TOC reduction) after 25 min of reaction. However, the coupling of this system with US showed an enhanced efficiency against the decolourization and mineralization of AR1. More than 95% colour removal was achieved within 5 min in the case of US/ZVINP system. Around 55% TOC reduction suggests the conversion of the parent molecules in to aromatic transformed products, and it is further supported by LC-Q-TOF analysis. The remarkably higher efficiency in the coupled system is attributed to the synergic effect of ZVINPs and ultrasound. The highest degradation rates observed at highly acidic (pH 3) and alkaline pH (pH 9) suggests that different mechanisms are operating at both pH. The products identified gave some insight into the mechanism. The ZVINPs prepared in the present study was easily recoverable (and reusable) and hence may be considered as an effective replacement for the conventional Fenton’s reagent.
... Among them, ozonation has been widely used in disinfection of drinking water and deep treatment of water pollution. Focusing on improvement of ozone decompostion to produce more hydroxyl radicals, a growing number of studies have been reported about combination of ozonation with other techniques such as O 3 -UV [6], O 3 -US [7], catalytic ozonation [8] and O 3 -H 2 O 2 [9,10]. Chen et al. proved that the effectiveness of combined technology of O 3 and fly ash [11,12]. ...
... It is evident from the Fig. 8b that increase in the initial pH (until the pH value of 10) decreased the pH of the medium during the reactive phase to acidic (Final pH). The drop in the solution pH during the reaction phase is mainly due to the formation organic acid as well as inorganic acid during UV irradiation of the dye solution [32,33]. Upon increasing the initial pH of the dye solution (from 10 to 12), no remarkable changes in the final pH was observed during the reactive phase due to the formation of weak organic acid as a reaction product. ...
Article
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Accumulation of large quantity of non-biodegradable textile dyes into the environment made much attention to finding a suitable solution for the degradation of textile dyes. In this present study, decolorization efficiency of two different treatment technologies such as Photo-Assisted Chemical Oxidation (PACO – UV/H2O2) and Electrocoagulation (EC) on Reactive Blue 194 dye solution (RB194) at different operational conditions were analyzed and the competitiveness of the treatment technologies in terms of energy consumption and operational costs were discussed. Even though both the processes follow different mechanistic approach for the degradation of dye solution, both the processes achieved more than 99% of decolorization efficiency. In terms of material/chemical consumption for the decolorization of dye solution PACO (US$ 0.016) competes with the EC (US$ 0.5937). But in terms of electrical energy consumption as well as the overall operating cost EC process compete (US$ 0.0481 & US$ 0.6418) with the PACO process (US$ 1.0267 & US$ 1.04337)
... It is evident from the Fig.1 that increase in the initial pH of the dye solution (from 3 to 10) decreased the pH of the reactive phase to acidic pH (Final pH). The drop in the solution pH during the reactive phase was mainly due to the degradation of the dye molecules and the formation organic acid as well as inorganic acid as byproduct of the degradation process during UV irradiation of the dye solution [17,18]. Upon increasing the initial pH of the dye solution (from 10 to 12), no remarkable changes in the final pH was observed during the reactive phase due to the formation of weak organic acid as a reaction products during this period of time. ...
Article
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Extend of decolorization of the dyes depends upon the complexity of the color causing chromophoric group in conjugation with auxochrome substituent present in the organic dye molecules. In this present study, decolorization efficiency of three class of organic dyes by Photo Assisted Chemical Oxidation process (PACO) were studied at different operational parameters such as initial pH, initial oxidant dose and initial concentration of organic dye solutions namely C.I. Reactive Blue 194 (RB), C.I. Direct Red 7 (DR) and C.I. Acid Violet 17 (AV). Variations in kinetics of decolorization of the organic dyes were also compared. Total treatment cost of PACO for decolorization efficiency of dyes were US$ 1.137 for RB at 20 mmol of oxidant, US$ 0.585 for RB at 30 mmol of oxidant, US$ 1.156 for DR at 50 mmol of oxidant and US$ 1.716 for AV at 50 mmol of oxidant per m3 of the dye solutions.
... And hydroxyl radicals were expected to form under acidic conditions during sonolysis of aqueous solutions [34]. From the study of He et al. [35], the reaction rate was low at low pH. However, ozone decomposition was gradually enhanced as the increasing of pH [36]. ...
Article
The effectiveness of ozone combined with ultrasound techniques in degrading reactive red X-3B is evaluated. A comparison among ozone (O3), ultrasonic (US), ozone/ultrasonic (O3/US) for degradation of reactive red X-3B has been performed. Results show that O3/US system was the most effective and the optimally synergetic factor reaches to 1.42 in O3/US system. The cavitation of ultrasound plays an important role during the degradation process. It is found that 99.2% of dye is degraded within 6min of reaction at the initial concentration of 100mg·L(-1), pH of 6.52, ozone flux of 40L·h(-1) and ultrasonic intensity of 200W·L(-1). Ozonation reactions in conjunction with sonolysis indicate that the decomposition followed pseudo-first-order reaction kinetics but the degradation efficiencies are affected by operating conditions, particularly initial pH and ultrasonic intensity. A kinetic model is established based on the reaction corresponding to operational parameters. In addition, the main reaction intermediates, such as p-benzoquinone, catechol, hydroquinone, phthalic anhydride and phthalic acid, are separated and identified using GC/MS and a possible degradation pathway is proposed during the O3/US process.
... Therefore, to enhance the degradation efficiency, many hybrid advanced oxidation processes (AOPs) such as electro-Fenton, UV/ H 2 O 2 , O 3 / H 2 O 2 photo-Fenton, and sonophotocatalytic process are used to degrade the effluent [10,11]. Various ferrites, oxyhalides, semiconductor oxides, and vanadates such as WO 3 , BiVO 4 , Cu 2 O, ZnO, CeO 2 , BiOBr, and GO are used as a photocatalyst [12][13][14][15]. In order to enhance the photocatalyst, various methods such as doping and composites of various catalysts are reported in the literature [16]. ...
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The aim of the present investigation is to study the different methods to improve the photocatalytic decolorization using visible light photocatalyst. In this investigation, ZnO/Bi2O3 composite was prepared using hydrothermal method, and it is studied for the decolorization of methylene blue (MB) dye. Enhancement of decolorization has been done by ultrasonication followed by photocatalytic process. Considerable improvement was observed in sonocatalysis followed by photocatalytic process. Various operating parameters have been studied and optimized for the maximum decolorization of dye wastewater. It is observed from the present result that the sonocatalysis followed by photocatalysis is found to be the more efficient method for the treatment of wastewater.
... Persistent organic pollutants are poorly biodegradable, meaning that natural processes cause very little decomposition of these compounds to occur, so these compounds can pollute the environment for a long time. Water is currently widely treated using activated sludge or activated carbon or using solid-liquid separation methods, but it is difficult to completely decompose persistent organic pollutants using these methods [2]- [6]. Attention has recently been paid to the use of advanced oxidation processes (AOPs) to remove persistent organic pollutants from water. ...
... It is rarely reported that the combined technology of O 3 and fly ash. Ozonation is an effective method to degrade dyes [7,8], pesticides [9,10], and landfill leachates [11]. Previous studies reported that the combination of ozonation with other techniques such as O 3 /UV, O 3 /US, catalytic ozonation and O 3 /H 2 O 2 can be proved more efficient. ...
Conference Paper
In order to control pesticide pollution in water environment, ozone-fly ash combined process was studied in laboratory. Dicamba(3,6-Dichloro-2-methoxybenzoic acid) was selected as model pollutant. The reaction temperature was changed to study the degradation efficiency. The experimental results show that fly ash taken from electric field II and III of ESP (No.2 fly ash) is finer than fly ash taken from electric field I of ESP (No.1 fly ash). Dicamba degradation using O3-No.1 fly ash system is faster than dicamba degradation using O3-No.2 fly ash system at same temperature. As the temperature increases, dicamba degradation is accelerated. The degradation can be well fitted by pseudo-first-order kinetics. The pseudo-first-order rate constant increases with temperature increases either in O3-No.1 fly ash system or in O3-No.2 fly ash system. The promote performance of finer No.2 fly ash on ozonation process is better than that of No.1 fly ash.
... Among them, ozonation has been widely used in disinfection of drinking water and deep treatment of water pollution. There are also a growing number of studies reported that the combination of ozonation with other techniques such as O 3 -UV [3], O 3 -US [4], catalytic ozonation [5] and O 3 -H 2 O 2 [6,7] can significantly improve the degradation efficiency. In our previous study [8], the effectiveness of the combined technology of O 3 and fly ash was proved. ...
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Managing environmental contamination with hydrolyzed polyacryamide (HPAM) is essential due to its persist long with slow biodegradability influence on the environment. In this study, the simultaneous combination of acoustic cavitation and microbubbles ozonation (US/O3) was applied to generate additional highly reactive hydroxyl radicals (·OH) and thus to enhance the degradation of HPAM. Compared with the two separated degradation process methods, the coupled method exerts a synergistic effect on the decomposition of HPAM, with an enhancement factor of 1.50. Effects of aeration pattern, ultrasound irradiation, operating temperature, initial HPAM concentration, and valance state of cations on the removal of HPAM were investigated intensively. An increase in valance state of cations contributes to HPAM removal. The maximum HPAM degradation, chemical oxygen demand (CODcr) removal and viscosity reduction of the HPAM wastewater were 97.35%, 89.01% and 93.25%, respectively. The degradation of HPAM conformed to the first-order reaction kinetic model. Removal of HPAM followed hydroxyl radical mechanism. The degradation mechanism of HPAM was also discussed with the change of FTIR and UV-Visible spectra of HPAM in investigated processes. The main reaction intermediates, such as heptanoic anhydride, oleamide, myristamide, acetic acid, acetamide, and propanamide, are identified and a possible degradation pathway is proposed during the US/O3 process. The process was proved to be a suitable technique for dealing with HPAM-containing wastewater.
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Azo dyes are widely used in textile and dyeing industry. Aniline, an important raw material of dyes and auxiliaries, is always the common by-products from the azo dye degradation, which is difficult to be completely removed in dyeing wastewater treatment. The discharge of azo dyes and aniline in textile wastewater arouses many environmental issues, and aniline is listed as the priority pollutant. In recent years, degradation techniques including physical, chemical and biological processes of different dyes and aniline have gained much attention. Their degradation pathways and corresponding mechanisms have been proposed. However, most studies focus on the dye removal or decolorization capacity, the influence factors, and the by-product varieties in certain degradation process. There were very few reports on the behavior of aniline transformation during the azo dye degradation processes, which is crucial for aniline control. This paper aims at comprehensively and critically reviewing the fate of aniline formation and degradation in different degradation technologies. Besides, crucial questions on aniline control are raised and discussed. It is expected that this work will shed new insight and provide valuable information that will aid in avoiding the environmental risk of aniline in textile and dyeing industry.
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Wastewater discharged by Batik’s industry still contains a high concentration of dyes and pollutants, thus can contaminate the water’s ecosystem. Because of that, in this study, Batik wastewater was treated by the hydrodynamic cavitation, ozonation, and combination of those two. By using PAC, a coagulation-flocculation-based pretreatment technic was conducted first to increase the effectiveness of the main wastewater treatment process. Then, variations in flow rate (2 L/min, 4 L/min, and 6 L/min) and initial pH of wastewater (4, 7, and 10) were evaluated to analyze its effect on the pH changing and the degradation of TSS, COD, color (Pt-Co), and TOC. The best result obtained from this research was by the application of the combination technic, which can eliminate 95.19%; 78.85%; 96.42%; and 60.56% of TSS, COD, color (Pt-Co), and TOC, respectively after 60 minutes treatment.
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Ozonation process is a crucial advanced oxidation process and has been commonly used for the degradation and mineralization of refractory pollutants. Ozonation water treatment process needs to transfer ozone from gas to the water phase. Although the solubility of ozone in water is higher than that of oxygen in water under the same conditions, it still belongs to the type of liquid film control in mass transfer. In the research of ozone oxidation process technology, enhancing the ozone-liquid mass transfer can improve ozone utilization efficiency and its technical economy. Therefore, numerous ozone-based process intensifications have been explored. This paper provided a summary of the application of external physical fields (ultrasonic field, hypergravity field, electric field, and magnetic/electromagnetic field) to strengthen ozone-liquid mass transfer and briefly explains the recent literature, which has applied the combination of external physical fields and ozonation to destroy organic compounds. The results show that ultrasonic can increase the mass transfer coefficient of ozone by 20%–200% under optimized conditions and ultrasound can generate free radicals through its cavitation. The hypergravity field can increase the mass transfer coefficient by at least 1.5 times. The addition of electric and magnetic fields also increases the mass transfer of ozone by more than 40% or more under optimized conditions.
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The decolorization of Reactive Blue 19 (RB 19) wastewater by an ozonation membrane contactor and Fenton oxidation was studied. The aims of the study were to investigate the affecting parameters and to compare the performance of RB 19 decolorization by two different processes. The results showed that Fe2+ and H2O2 concentrations for Fenton oxidation and ozone concentration with different membranes for the membrane contacting process played the most important roles in RB 19 decolorization. The optimum conditions for RB 19 decolorization by Fenton oxidation were initial pH 3.0, 1.5 mM H2O2 and 0.25 mM Fe2+; in contrast, the optimum conditions for the membrane contactor were initial pH 11 and 40 mg L-1 ozone concentration. Under these conditions, the decolorization of RB 19 by the membrane contactor was almost completed and was higher than by Fenton and photo-Fenton oxidations for 90 min. The decolorizations of RB 19 by Fenton and photo-Fenton oxidations were constant after 30 min, but the decolorization of RB 19 by ozonation with a membrane contactor gradually increased via ozone consumption until 90 min operation, which was higher than that of Fenton oxidations. The use of a PVDF-PAM membrane in the membrane contactor resulted in higher decolorization efficiency than a PVDF membrane. The results demonstrated a COD removal efficiency of 63% by an ozonation membrane contacting process using PVDF-PAM, which was lower than that of Fenton oxidation (73%), but resulted in higher BOD5/COD and NO3 - and SO4 2- releases. Under these conditions, the ozonation membrane contacting process showed the lowest electric energy consumption.
Chapter
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Gravity-driven membrane (GDM) filtration is a membrane process that utilizes hydrostatic pressure to drive the separation. In a long-term operation a permeable biofilm layer is formed on the membrane surface which induces a stable flux that enables longer operation without any cleaning or flushing. The stabilization of the permeate flux depends on the structure and composition of the developed biofilm, which is affected by several including the quality of the feedwater and the operational conditions. In addition to the flux stabilization, GDM process also benefits better organic removal and rejection by the biofilm. The GDM system is very attractive for decentralized water and wastewater treatment, particularly due to the low energy demand and easy maintenance. This chapter overviews the GDM process and discusses factors affecting its performance.
Chapter
Sonolysis and ozonation are two advanced oxidation processes (AOPs) that are actually well documented and their mechanisms are well established. Recently, the combination of these two processes, that is sonolytic ozonation [ultrasound (US)/O3], has been successfully applied to improve the degradation of several water contaminants, as compared to each process separately. The mechanism by which US enhances the ozonation process and vice versa is utile now under discussion. Ozone injection can create more nucleation sites and improve the cavitation events by increasing the number of bubbles. Furthermore, US may enhance the mass transfer of O3 in the liquid. Besides, ozone can be thermally decomposed inside pulsing acoustic bubbles, which provokes reaction chain leading to higher rate of •OH generation. However, the use of high O3 concentration can decrease the sonochemical activity through favoring bubbles coalescence, which is considered as the main suppressor of inertial cavitation responsible for all chemical effects of US. The present study aimed at (1) giving an overview of the US/O3 sono-hybrid process and (2) illustrating the synergetic mechanisms of the process through confronting simulation results with experimental data. The simulations results provide the effect of ozone presence in the aqueous solution on the chemical yield, that is •OH production rate, of single acoustic bubble at various operating conditions of frequency, acoustic intensity, and ozone concentration. Based on results, a conceptual diagram for the chemical activity of the US/O3 process has been made.
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Degradation activity of plasma catalysis between dielectric barrier discharge (DBD) and carbon nanotubes-graphene-nickel foam (CNTs-G-Nif) has been studied in treatment of dye wastewater. CNTs-G-Nif was prepared through a two-step chemical vapor deposition (CVD) approach. The composite has been characterized by different techniques such as X-ray diffraction (XRD), scanning electron microscope (SEM) and Raman spectroscopy. SEM results showed that the Nif as the growth substrate was evenly wrapped by G and then CNTs were successfully grown on G as the support. The growth mechanism of composite was proposed. The possible coupled catalytic mechanism between DBD and CNTs-G-Nif were addressed. In addition, the modification on G-Nif was found by SEM during the discharge process in liquid phase. And the modification mechanism of DBD plasma (DBDP) acting on composites was discussed. Finally, by means of analyses of ultraviolet-visible (UV-Vis) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS), the general degradation pathway and stepwise degradation pathways of alizarin green (AG) were proposed in detail. HIGHLIGHTS A novel degradation system DBD plasma/CNTs-G-Nif is proposed.; The new model of coupling factor is put forward to evaluate the degradation effect.; DBD plasma has modification on G-Nif in degradation of dye wastewater.; Comprehensive mechanisms of preparing,coupling,modifying and degrading are explored.;
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In this study, a heterogeneous activator was prepared via the Fe/Mn modification of sludge-derived biochar (Fe/MnBC) to achieve high-efficiency activation of persulfate (PS) for reactive blue 19 (RB19) degradation. The morphologies and chemical states of Fe/MnBC were examined by various characterizations. A comprehensive assessment was conducted to reveal the effects of biochar preparation conditions and system reaction conditions. According to the results of scavenger quenching experiments and electron paramagnetic resonance (EPR) testing, the mechanisms of Fe/MnBC combined PS system on RB19 degradation were proposed, including radical and non-radical mechanisms. The formation and involvement of sulfate radical (SO4·−), hydroxyl radical (OH·), and singlet oxygen (¹O2) were proved in this system, and Fe(IV)/Mn(VII) was also speculated to participate in the non-radical degradation process. These findings give a new insight into the mechanisms of PS activated by metal-biochar composite. Besides, fixed-bed reactor (FBR) experiments indicated that the Fe/MnBC has considerable PS activation potential for dyes removal. The degradation process was further modeled by the central composite design (CCD-RSM) and artificial neural networks (ANN) methods. The statistical metrics and prediction indicated that the prediction results of ANN model were better than CCD-RSM model, and the ANN model could perfectly predict the reaction process of Fe/MnBC FBR for engineering applications.
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A novel multiphase tank reactor with foam block stirrer, also called rotating foam stirrer reactor (RFSR), was used to intensify ozone mass transfer and oxidation of synthetic textile wastewater processes for the first time. Results show that the RSFR can improve the ozone mass transfer process by adjusting operation conditions and gas hydromechanics. In order to predict the volumetric mass transfer coefficient, a set of correlation was developed within ±15% deviation. Further, based on an Acid Red B (ARB) solution used as simulated synthetic textile wastewater, it was found that the removal efficiency was improved by intensifying ozone mass transfer process, and changing operation conditions can promote the transformation of the ozone oxidation path to an indirect reaction way. Finally, results show that the Fe-Co oxides coated on the foam block stirrer can further intensify the degradation processes in the ARB solution. This study gives a fundamental understanding of the intensification mechanism of the RFSR and shows the promising prospect of an RFSR used in in the wastewater treatment.
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The presence of recalcitrant organic compounds such as pharmaceuticals, personal care products, hormones and antibiotics in the aquatic environment is a growing concern as they are resistant to conventional treatment processes. Many of these compounds are categorized as contaminants of emerging concerns (CECs). Ozonation process is highly effective but it is usually restricted by the poor mass transfer rate of ozone into the water. Hybrid ozonation-ultrasonication system has been emerging as an efficient method for the rapid removal of these stable compounds due to the synergy between the two effects. The process is technically simple, more effective and achieves fast degradation with no addition of chemicals is necessary. Mature understanding on the hybrid system is however yet to be established. In this manuscript, a detailed review is conducted on the fundamental issues regarding ozonation-ultrasound (US/O3) hybrid process. Phenomena towards the synergy between the two effects, the degradation potential, the optimum parameters, the possible reaction mechanism and the reaction kinetics are critically reviewed. Reported performances in the removal of some CECs are compared and analyzed. Besides, a few recommendations for future research direction with regards to the CECs reactivity, suitable system set up, operational cost etc. are also made.
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In this study, the main influence factors of combined UV/O3 process in practical industrial application were explored through laboratory trials and industrial pilot tests. Dimethyl phthalate (DMP) was analyzed as the research subject through different experiments in laboratory. The degradation effect of organic compounds by O3 and UV/O3 processes in different air distribution methods was compared independently, and the mechanism of free radical generation by the two processes was analyzed. This study found that the combined UV/O3 process for organic matter mineralization is clearly better than that of independent effect of O3 process as mixed gas-liquid distribution method was superior to the bubble aeration method. The experimental conditions included inlet O3 concentration between 70-75 mg/L, reactor internal relative pressure at 0.3 MPa, contact reaction time of 12 min, DMP mineralization efficiency reaching 63.07%. The calculated dosing ratio of O3 in the dynamic experiment was around 0.74 mg CODCr/mg O3. The results showed that the best effect in wastewater treatment was achieved when the conditions of ultraviolet lamp irradiation intensity and the O3 dosage reached 822.88 W/m² 15 mg/L and utilized in conjunction with biochemical reactions. The resulting CODCr concentration of effluent reached 39.8 mg/L. Finally, it is determined that the main influence factors affecting the economically efficient operation of UV/O3 process were the efficient O3 distribution mode, control of the relative pressure within the reactor, proportion of ozone addition and light source configuration.
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Up to 84,000 tons of dyes can be lost in water and 90 million tons of water are attributed annually to dye production and their application, mainly in the textile and leather industry, making dyestuff industry responsible for up to 20% of the industrial water pollution. The majority of dyes industrially used today are aromatic compounds with complex, reinforced structures, with anthraquinone dyes being the 2nd largest produced in terms of volume. Despite the progress on decolourisation and degradation of azo dyes, very little attention has been given to anthraquinone dyes. Anthraquinone dyes pose a serious environmental problem as their reinforced structure makes them difficult to be degraded naturally. Existing methods of decolorisation might be effective but are neither efficient nor practical due to extended time, space and cost requirements. Attention should be given to the emerging routes for dye decolorisation via the enzymatic action of oxidoreductases, which have already a strong presence in various other bioremediation applications. This review will discusses the presence of anthraquinone dyes in the effluents and ways for their remediation from dyehouse effluents, focusing on enzymatic processes.
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Wastewater produced by the textile industry containing azo dyes and anthraquinone dyes is significant source of pollution to the environment and is toxic for aquatic life. To overcome the high‐energy cost of traditional electrochemical oxidation, a custom‐built power supply device for the degradation of anthraquinone and azo dyes by low voltage of 15.0–20.0 V pulsed discharge was investigated. Titanium coated with mixed oxide (Ti/IrO2‐RuO2‐SnO2) plates and pure titanium plates were used as the anode and cathode, respectively, for the generation of chlorine in the dye solution. For the anthraquinone dye Reactive Blue 19, 60.0% of the chemical oxygen demand (COD) and 22.0% of the total organic carbon (TOC) were removed using this system. A comparison of the direct current electrolysis and pulsed discharge revealed that using the pulsed discharge method reduced the energy cost by 68.6%. UV–visible, LC‐MS, and GC‐MS were used to identify the intermediate compounds formed during the degradation of Reactive Blue 19. The results indicate that in the process of oxidation by chlorine/hypochlorite, the chromophore group was first oxidized to –NH2, followed by decolorization via chlorination of the aromatic rings. The results confirm that low‐voltage pulse electrolysis can be used for the degradation of industrial dyes in waste effluents. Practitioner points • Low‐voltage pulse electrolysis can be used for the degradation of industrial dyes and/or dyes in waste effluents. • For anionic dye Reactive Blue 19, 60.0% of COD and 22.0% of TOC were removed using low‐voltage (20.0 V) pulse electrolysis. • The pulsed discharge method reduced the energy cost of this degradation process by 68.6% compared with direct current electrolysis. • The intermediate compounds formed during the degradation of Reactive Blue 19 were confirmed by UV–visible spectroscopy, LC‐MS, and GC‐MS.
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In this study, a newly screened mixed bacterial flora DDMY2 had high decolorization capacity for anthraquinone dye reactive blue 19 (RB19) and the decolorization efficiency of 300 mg L-1 RB19 could reach up to 98% within 48 h in the presence of tea residue. Results indicated that RB19 could be efficiently decolorized by flora DDMY2 in wide ranges of pH values (5.0-9.0), temperatures (30-40 °C) and initial dye concentrations (50-500 mg L-1) under the activation of tea residue. Concentration of tea residue had been proved to significantly impact the decolorization performance. UV-vis spectrophotometry, Fourier transform infrared spectrometry and liquid chromatography/time-of-flight/mass spectrometry analysis showed three identified degradation products and the possible degradation pathway of RB19 was speculated. High-throughput sequencing analysis revealed the community structures of bacterial flora before and after domestication by tea residue. Based on the result, it was inferred that unclassified_o_Pseudomonadales, Brevibacillus, Stenotrophomonas and Bordetella activated by tea residue were responsible for the excellent decolorization performance. Results of this research deepen our understanding of the biodegradation process of anthraquinone dyes by bacterial flora and broaden the knowledge of utilizing tea residue as a bioactivator in biological treatment.
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In recent years, ozonation combined with ultrasound (US/O 3 process) has been actively researched as a promising method of advanced oxidation processes. Comparing with ozonation or ultrasound alone, it appears to be more effective and uses less energy, and it has the advantages of being nonselective, leading to no secondary pollution, and being particularly effective in removing persistent and biorefractory pollutants from water. This review describes the recent progresses in US/O 3 process for the degradation of persistent and biorefractory pollutants. Based on results, a global conceptual diagram for possible pathways of substrate degradation in US/O 3 system was given. Finally, some interesting trends and perspectives for this emerging area of research have been reported together with some highlighting needs to innovative.
Chapter
The effluents from the textile processing industry cause great environmental and human health concerns; development of an eco-friendly and energy-efficient technique to treat such effluents has been a major challenge. The conventional wastewater treatment methods have been ineffective to remove textile pollutants, due to the high toxicity and chemical stability of such pollutants. Advanced oxidation processes have been proven to be the most appropriate and most efficient techniques for the treatment of textile pollutants because of their cost- effectiveness, high performance, and lower consumption of materials and reagents. The main objective of this chapter is to provide effective treatment methods based on process intensification (PI), which consists of chemical and process design approaches that lead to substantially smaller, cleaner, safer, and more energy-efficient processes. This chapter mainly focuses on the application of novel process technologies to achieve significant size reduction in individual unit operations, or the complete removal of process steps by performing multiple functions in fewer steps. These should lead to overcome the problems that restricted the practical applications of wastewater treatment and cause significant reductions in capital and running costs, and improvements in process efficiency and safety.
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Bu çalışma kapsamında endüstriyel atıksuların arıtımında kullanılan ileri oksidasyon proseslerinden H2O2 (hidrojen peroksit) / UV (Ultraviyole) kullanımının C.I. Reactive Black 5 boyarmaddesinin fotokatalitik olarak renk giderimine etkisi araştırılmıştır. Numuneler hidrojen peroksit başlangıç konsantrasyonu, sıcaklık, pH, renk ve KOİ (kimyasal oksijen ihtiyacı) değerleri açısından incelenmiştir. Belirlenen koşullar altında renk giderim verimleri 0,5 ml/l H2O2 konsantrasyonunda nötr ortamda %99,71, asidik ortamda %99,76, bazik ortamda %94,81 ve KOİ giderim verimi ise sırasıyla %38,91 %41,44 ve %20,73 olmuştur. 0,5 ml/l H2O2 başlangıç konsantrasyonunda renk gideriminin en hızlı (55. dk’da %99 renk giderim oranı) asidik ortamda gerçekleştiği gözlenmiştir. En hızlı renk giderimi sonuçlarına ulaşılan asidik ortamda hidrojen peroksit başlangıç konsantrasyonu değiştirilerek denemeler yapılmıştır. Yapılan bu denemelerdeki 0,5 ve 2,5 ml/l H2O2 konsantrasyonları karşılaştırıldığında konsantrasyon artışının renk giderim hızını artırdığı gözlenmiştir (%99 renk verimine ulaşılan süre: 30 dk) ancak 2,5 ml/l ve 5 ml/l H2O2 konsantrasyonları arasında hidrojen peroksit miktarındaki artışa değecek bir fark gözlenmemiştir. Sonuç olarak yapılan denemelerde C.I. Reactive Black 5 için elde edilen fotokatalitik renk giderim verimi; endüstriyel atıksuların arıtımında H2O2/UV uygulamasının başarıyla kullanılabilir olduğunu göstermiştir.
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Background and purpose: Colors are toxic organic materials with complex structures used in textile production stages such as dyeing, finishing and printing that cause environmental problems. One of the most widely used colorant in textile is reactive blue 19 dye. This study aimed to examine the feasibility of TiO2 as catalysts and sonochemistry process for discoloration of reactive blue 19 from aqueous solutions. Materials and methods: The study was conducted in laboratory scale. The effect of different parameters affecting the decolorization of reactive blue 19, including the amount of TiO2 nanoparticles, pH, initial dye concentration and the time was investigated. The remaining concentration of RB19 was analyzed by UV-Vis carry 100 spectrophotometer at a wavelength of 592 nm. The response surface methodology was used based on central composite design (CCD) to evaluate the effect of independent variables on the removal efficiency and to predict the best answer. This model with ANOVA analysis confirmed the significant effect of variables. Results: The experiments and 3D plots showed that higher decolorization was obtained in neutral pH and decolorization efficiency was decreased with increment of initial dye concentration. The highest decolorization was achieved at 62 min and additional time was not effective on decolorization. In current study, 94.7 % discoloration was achieved in optimum conditions, namely 0.08 g/L RB19, pH=6.0, and 1.63 g/L TiO2 at 62.5 min. Conclusion: The proposed method could be considered as green method for discoloration of colorful pollutant because it does not use oxidant chemicals such as hydrogen peroxide or hypochlorite, which their residues are harmful to the environment.
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The degradation of organic pollutants in the simulated and realistic wastewaters was investigated by Fe-C micro-electrolysis system. Effects of initial pH, Fe/C mass ratio, gas bubbling type (air or N2) and the type of anions on degradation and mineralization of Sunset Yellow (SY) were studied. The degradation and mineralization efficiencies of 500 mg·L⁻¹ SY were approximately 99.0% and 77.5% after 90 min treatment, when the initial pH, Fe/C ratio and air bubbling flow rate were 6.0, 1:1 and 45 L·h⁻¹, respectively. Besides, the type of anions had a significant influence on the Fe-C micro-electrolysis process. The results of kinetics study indicated that Fe-C micro-electrolysis process followed Second-order-kinetics well. The degradation pathway and mechanism for SY were proposed based on FTIR and LC-MS analyses of treated wastewater. Additionally, the Fe-C micro-electrolysis process could dispose linear alkyl chain and benzene ring compounds efficiently under the optimal conditions, and the mineralization efficiencies were in the range of 94 - 96% and approximately 80%, respectively. The degradation feasibility of a realistic wastewater by the Fe-C micro-electrolysis system was investigated with landfill leachate. In conclusion, Fe-C micro-electrolysis system is an effective and promising technology for organic wastewater treatment in near-neutral pH condition.
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This research investigated the discoloration and mineralization of Reactive Blue 19 (RB19) anthraquinone dye by single ozonation, single UV radiation and ozonation jointed with UV radiation (O3 /UV). The problem was approached from two points of view: with the objective of color removal or the mineralization of solution. In each case, the optimum operating conditions were different. Ozonation was the most effective treatment for color removal, while the combined O3/UV treatment was for mineralization. Major intermediates of the dye degradation were identified by gas chromatography/mass spectrometry and a degradation pathway was proposed. In addition, a clear decrease of the toxicity of the dye was achieved at the end of the experiments. The effect of initial dye concentration, pH, ozone dose, and UV radiation on the degradation of the dye and decrease of total organic carbon was investigated, in order to establish the optimal operating conditions to achieve discoloration, mineralization or a combination of both.
Article
In this study, the dynamic adsorption of methylene blue dye onto CuO-acid modified sepiolite was investigated. Meanwhile, the equilibrium and kinetic data of the adsorption process were studied to understand the adsorption mechanism. Furthermore, a high-temperature gas stream was applied to regenerate the adsorbent. The results showed that the Langmuir isotherm model was applied to describe the adsorption process. The positive value of enthalpy change indicated that the adsorption process was endothermic in nature. In the dynamic adsorption process, the best adsorption performance was achieved when the ratio of column height to diameter was 2.56 and the treatment capacity was 6 BV/h. The optimal scenario for regeneration experiments was the regeneration temperature of 550-650 °C, the space velocity of 100 min(-1) and the regeneration time of 10 min. The effective adsorption of CuO-acid modified sepiolite was kept for 12 cycles of adsorption and regeneration.
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A new methylene blue molecularly imprinted polymer (MB-MIP) was synthesized by inverse microemulsion polymerization with methylene blue (MB) as the imprinted template molecules. It exhibited higher selectivity in comparison with the nonimprinted polymer (NIP), and the maximum adsorption amount of the MB-MIP for MB reached 3628.84 mg g−1, which was even higher than activated carbon at high MB concentrations. Compared with gentian violet (GV) and malachite green (MG), MB-MIP has the highest affinity to MB. In addition, the adsorption property of MB-MIP were well represented by the pseudo-second-order kinetic model, the Langmuir isotherm model, and the Weber-Morris model, indicating that the adsorption process is chemical adsorption and the main process of the adsorption rate-controlling step was particle internal diffusion. The adsorption thermodynamic parameters ΔG 0 show that the adsorption process was spontaneous.
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The sonolysis of 4-nitrophenol (4-NP) and aniline in O2-saturated aqueous solutions was performed at 610 kHz with ultrasonic power of 25 W and aqueous temperature of 15±1°C. The initial rate of degradation of both 4-NP and aniline in sonolysis of aqueous media follows pseudo-first-order reaction kinetics. Investigation of the H2O2 generation rate in phosphate buffer media (0.01 M) over the range of pH 2–9 revealed a maximum yield at pH ≈3.2. The pH, which results in modification of the physical properties (including charge) of molecules with ionisable functional groups, plays an important role in the sonochemical degradation of chemical contaminants. For hydrophilic substrates, the neutral species more easily diffuse to and accumulate at the hydrophobic interface of liquid–gas bubbles in comparison with their corresponding ionic forms. As a consequence, the degradation rate of 4-NP under ultrasonic irradiation decreases with increasing pH. In contrast, the disappearance rate of aniline exhibits a maximum under alkaline conditions due to the high solubility of the ionic anilinium ion and the (potentially) preferential movement of the uncharged form to the interface. Additionally, the rate of reaction of the uncharged aniline molecule (which dominates at pH>4.6) with hydroxyl radicals is reported to be about three times as fast as the rate of reaction of the cationic anilinium species.
Article
The decolorization of two different textile dyes, Reactive Red 2 and Reactive Blue 4, was studied in batch as well as continuous experiments using Bjerkandera sp. Strain BOL 13. The batch experiments were performed to study the decolorization of the dyes separately as well as in a mixture. The results from the experiments showed that the fungus decolorized both dyes. The absorbance was measured at 538 and 595nm, the peak absorbance wavelengths of the red and blue dyes respectively. The absorbance decreased with 99% at both 538 and 595nm in the experiments in which the dyes were studied separately at a concentration of 100mg/l. The corresponding figure for the experiment in which the dyes were studied in a mixture was 98%. A continuous rotating biological contactor was then used to study the decolorization of mixtures of the two dyes at three different concentrations, e.g. 50, 100 and 200mg/l of each of the dyestuff. The decrease in absorbance at 538nm was 96% at the two lower dye concentrations while it was 81% at the highest concentration. The corresponding figures at 595nm were 94 and 80%. The hydraulic retention time was 3 days. Scanning of the absorbance between 200 and 800nm showed that three peaks disappeared in the UV range during treatment (246, 283 and 323.5nm) and that a new plateau was formed around 270nm.
Article
The calorimetric method and the Weissler reaction were reevaluated as a means to standardize the ultrasonic power of individual ultrasonic devices. Results showed that the Weissler reaction, which can be regarded as a chemical dosimeter for measuring acoustic energy, was directly and linearly related to the calorimetrically determined ultrasonic power; the latter was independent of the volume and shape of a vessel, even if ultrasound was introduced using different devices. The additional description of either the calorimetrically determined power or the chemical yield of the Weissler reaction as one of the reaction conditions to ascertain the level of ultrasonic power in the research report is proposed.
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The effluent from dye manufacturing plant is generally recalcitrant to be decolourized visibly because of versatile composition resulting environmental problem. Hence, the UV/H2O2 process conducted using the recirculated batch reactor system with four annular UV lamps was proposed to treat the dye plant effluent in this work, while identifying the effects of hydrogen peroxide dosage, UV power input and wastewater strength on the decolouration and COD removal. From the experimental results, substantial decolouration and COD removal was increased significantly by supplementing hydrogen peroxide dosage, UV power input. Moreover, the pseudo-first order model was developed to describe the decolouration behaviour that the kinetic rates were calculated by linear regression obtaining the decolouration rate constant of 0.0993mins−1 while 72.0Wl−1 of UV power and 116.35mM of H2O2 dosage for 10% diluted plant wastewater with PtCo colour of 4550 units and COD of 1065mgl−1. Ultimately, the proposed recirculated four-lamp annular UV/H2O2 reactor conducted profitably to not only decolourize but also mineralize the dye plant effluent at the same time.
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Al–Cu pillared clays were prepared by direct introduction of Al–Cu pillaring solution into the dilute bentonite suspension. Al–Cu pillared clays had d001 spacing of about 18Å and had surface area of about 140m2/g or higher. Al–Cu pillared clays showed excellent activity toward the catalytic wet peroxide oxidation (CWPO) of reactive dyes. Complete removal of reactive dyes could be achieved within 20min at atmospheric pressure and 80°C which are extremely milder operation condition when compared with the conventional catalytic wet oxidation process. The pillared clays were also stable against the leaching out of Cu.
Article
The degradation of a reactive dye by combined sonolysis (520 kHz) and ozonation was studied using C.I. Reactive Black 5 as a model dye. It was found that the joint action of ultrasound and ozone induced a synergistic effect on both the decolorization of the dye and the overall degradation process. Due to the inefficiency of ultrasonic irradiation by itself to render any significant degradation under the conditions employed, the synergy was attributed mainly to mechanical effects of ultrasound to enhance the mass transfer of ozone in solution. The radical chain reactions taking place during thermolysis of water and ozone in collapsing cavities may also have contributed chemically to the synergy by providing additional decomposition pathways for ozone, and an excess of electron-deficient chemicals in solution.
Article
The decomposition of pentachlorophenol (PCP) by sonication was investigated at two frequencies (20 and 500 kHz) and two concentrations (20 and 60 μM) to gain insight into the kinetics and mechanisms occurring at different frequencies. Results suggest the presence of parallel pyrolysis and OH• reaction pathways that are altered both as a function of frequency and PCP concentration. In addition, ozone was added to the system and compared to experiments of sonication and ozonation separately to explore the mechanism of sonolytic ozonation. The addition of ozone during sonication did not affect the first-order degradation constant for PCP compared to the linear combination of separate sonication and ozonation experiments; hence, the residual kinetic effect of the combined system was zero (kUS/O3 = 0). Observed byproducts of sonication include the following:  tetrachloro-o-benzoquinone (o-chloranil), tetrachlorocatechol (TCC), oxalate, and chloride.
Article
The sonolytic degradation of ozone (O3) was investigated in both closed and open continuous-flow systems to examine effects of mass transfer on chemical reactivity in the presence of ultrasound. Degradation of O3 followed apparent first-order kinetics at frequencies of both 20 and 500 kHz in all the systems. Degassing of O3 was observed at 20 kHz due to the effects of rectified diffusion and larger resonant radii of the cavitation bubbles than at 500 kHz. Increased mass transfer of O3 diffusing into solution due to ultrasound as measured by the mass transfer coefficient, kLa2, was observed at both frequencies. At 20 kHz, an increase in mass transfer rates in the presence of ultrasound may be partially attributed to turbulence induced by acoustic streaming. However, the main process of increased gas−liquid mass transfer in the presence of ultrasonic waves appears to be due to the sonolytic degradation of O3 creating a larger driving force for gaseous O3 to dissolve into solution. From first-order cyclohexene degradation kinetics obtained by sonolysis, ozonolysis, sonolytic ozonolysis, and comparing the large diameter of an O3 diffusing gas bubble to the size of an active cavitation bubble, it appears that diffusing gas bubbles containing O3 are not directly influenced by ultrasonic fields.
Article
Wet air oxidation (WAO) is effective in the oxidation of 5-nitro-o-toluenesulfonic acid (NTSA); the WAO reaction is first-order with respect to NTSA. Sulfur initially present is almost stoichiometrically converted to sulfate. A significant amount of nitrogen gas and ammonium are present in the reactor offgas and WAO effluent, respectively. No NO(x) or SO(x) is detected. Proposed reaction pathways are presented for the WAO of NTSA, based on the intermediates and end products identified. NTSA concentration up to 150 mg/L does not show inhibitory effects on enriched Nitrosomonas. However, WAO-treated NTSA does show some adverse effect on the nitrite production capability of the Nitrosomonas, thus indicating that some byproducts formed during WAO of NTSA may be more toxic than NTSA itself.
Article
The primary step in the thermal decomposition of acidic aqueous ozone solutions is the dissociation reaction: O3 reversible O + O2. This reaction is supported by the retarding effect of O2 on the decomposition rate, by our activation energy measurements, E(A) = 79.5 +/- 8.0 kJ mol-1, and by isotopic exchange experiments with O-18(2),O-18(2). The rates of ozone decomposition were measured at pHs O-4, at temperatures 0-46-degrees-C, and at O2 concentrations 10(-5)-10(-3) M. The O atom formed in the dissociation reaction is postulated to be the precursor for OH and HO2 formation. The ionization of the HO2 free radical (pK = 4.8) accounts for the increase in rate with rising pH. The mechanistic implications of O3 decomposition in acid solution are briefly discussed.
Article
The ozonation of wastewater supplied from a treatment plant (Samples A and B) and dye-bath effluent (Sample C) from a dyeing and finishing mill and acid dye solutions in a semi-batch reactor has been examined to explore the impact of ozone dose, pH, and initial dye concentration. Results revealed that the apparent rate constants were raised with increases in applied ozone dose and pH, and decreases in initial dye concentration. While the color removal efficiencies of both wastewater Samples A and C for 15 min ozonation at high ozone dosage were 95 and 97%, respectively, these were 81 and 87%, respectively at low ozone dosage. The chemical oxygen demand (COD) and dissolved organic carbon (DOC) removal efficiencies at several ozone dose applications for a 15 min ozonation time were in the ranges of 15–46% and 10–20%, respectively for Sample A and 15–33% and 9–19% respectively for Sample C. Ozone consumption per unit color, COD and DOC removal at any time was found to be almost the same while the applied ozone dose was different. Ozonation could improve the BOD5 (biological oxygen demand) COD ratio of Sample A by 1.6 times with 300 mg dm−3 ozone consumption. Ozonation of acid dyes was a pseudo-first order reaction with respect to dye. Increases in dye concentration increased specific ozone consumption. Specific ozone consumption for Acid Red 183 (AR-183) dye solution with a concentration of 50 mg dm−3 rose from 0.32 to 0.72 mg-O3 per mg dye decomposed as the dye concentration was increased to 500 mg dm−3.© 2002 Society of Chemical Industry
Article
The reaction mechanism and pathway of the ozonation of 2,4,6-trichlorophenol (2,4,6-TCP) in aqueous solution were investigated. The removal efficiency and the variation of H2O2, Cl− formic acid, and oxalic acid were studied during the semi-batch ozonation experiments (continuous for ozone gas supply, fixed volume of water sample). The results showed that when there was no scavenger, the removal efficiency of 0.1 mmol/L 2,4,6-TCP could reach 99% within 6 min by adding 24 mg/L ozone. The reaction of molecular ozone with 2,4,6-TCP resulted in the formation of H2O2. The maximal concentration of H2O2 detected during the ozonation could reach 22.5% of the original concentration of 2,4,6-TCP. The reaction of ozone with H2O2 resulted in the generation of a lot of OH• radicals. Therefore, 2,4,6-TCP was degraded to formic acid and oxalic acid by ozone and OH• radicals together. With the inhibition of OH• radicals, ozone molecule firstly degraded 2,4,6-TCP to form chlorinated quinone, which was subsequently oxidized to formic acid and oxalic acid. Two reaction pathways of the degradation of 2,4,6-TCP by ozone and O3/OH• were proposed in this study.
Article
The removal efficiency of 4-chlorophenol by ozonation was studied, and the reaction mechanism and characteristic of ozonation of 4-chlorophenol were investigated. Ozone and hydroxyl radicals are two strong oxidants during the process of ozonation. The experimental results showed that when there was no scavenger to inhibit OH· radicals, an intermediate product, hydrogen peroxide was formed during the ozonation of 4-chlorophenol. Hydrogen peroxide reacted with ozone at neutral pH and produced hydroxyl radicals. Ozone at the dosage of 113 mg/L could remove 20 mg/L 4-chlorophenol and 39% TOC. With the complete inhibition of hydroxyl radicals, molecular ozone could effectively destroy 4-chlorophenol to form 4-quinone, which was subsequently oxidized to formic acid and oxalic acid. Two reaction pathways of the degradation of 4-chlorophenol by ozone and O3/OH· were proposed in this study. Ozonation is an effective method for reducing 4-chlorophenol, and has potential to practical application.
Article
Analysis and characterization of the textile dye C.I. Reactive Blue 4 (RB4), a commercially important anthraquinone dye, as well as its hydrolysis products, were conducted by spectrophotometry, high performance liquid chromatography (HPLC), as well as advanced mass spectrometric techniques. Although spectrophotometric analysis can be used for the routine quantification of RB4 in aqueous solutions, HPLC analysis is necessary for the quantification of the unhydrolyzed, monohydroxy- and dihydroxy-RB4. The effect of both salt and base at concentrations typically used in reactive dyeing on the dye spectra was also investigated. Although moderate dye aggregation, leading to absorbance depression, was observed at relatively high dye and salt concentrations (1000 mg/l and 100 g/l, respectively), spectrophotometric and HPLC analysis was possible as long as the effect of salt and base was taken into account in the development of standard calibrations. Liquid chromatography/electrospray ionization-mass spectrometry (LC/ESI-MS) and matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS) analyses led to the separation and identification of the parent RB4 molecule. LC/ESI-MS analysis of RB4 solutions led to the conclusive identification of the two RB4 hydrolysis products, as well as one impurity. Values of physico-chemical properties of RB4 were estimated using two software packages. The estimated RB4 LC50 value for acute toxicity to fish (1500 mg/l) agreed well with the acute toxicity EC5015 min value measured by the Microtox® procedure (1108 mg/l). Although the levels of RB4 in the environment are expected in the orders of magnitude lower than these LC50 and EC50 values, the effect of long-term, low-level dye exposure needs to be evaluated.
Article
The oxidation of C.I. Reactive Blue 4 (RB4) by photo-Fenton process mediated by ferrioxalate was investigated under artificial and solar irradiation. The RB4 degradation in acidic medium (pH 2.5) was evaluated by the decrease in Total Organic Carbon (TOC) content and color, measured by the decrease in chromophore absorption band (600 nm). The influence of ferrioxalate and H2O2 concentrations on the dye degradation was studied and best results were obtained using 1.0 mM ferrioxalate and 10 mM of hydrogen peroxide. Under these experimental conditions, 80% of TOC and 100% of color removal were obtained for a 0.1 mM RB4 dye in 35 min of solar irradiation.
Article
The photodegradation of orange II by TiO2 supported on three adsorbents namely MCM-41, Montmorillonite and β-Zeolite was studied under different conditions. The surface properties of the catalysts varied with solution pH and strong adsorption of orange II occurred at low pH (below pHPZCof the supported catalysts), while the maximum photodegradation rate occurred at an optimum pH range of 4–5 for the supported catalysts as compared to 2.5 for the unsupported TiO2 (Degussa P25). Although the adsorption and subsequent photodegradation of orange II were better for the supported catalysts compared to the unsupported TiO2, complete mineralization occurred only in presence of small amount of ozone, but at lower power consumption as compared to Degussa P25. The results indicate that TiO2 supported on porous adsorbents is a potential catalyst system for the continuous removal of complex organics from water.
Article
As a continuation of part I [Dyes and Pigments 42 (1999), 123] where modeling of H2O2/UV decoloration of monochlorotriazine azo dye C.I. Reactive Red 120 was discussed, this part deals with the study of the effects of the variables on H2O2/UV decoloration of reactive vinylsulpone dye C.I. Reactive Blue 19. Influence of chemicals (NaOH, NaCl, urea), added to the dye-bath for dyeing with stated colorant, as well as the influence of reaction conditions (intensity of UV irradiation, concentration of hydrogen peroxide and decoloration time) is described. Influences were determined by the measurement of ecological parameters: absorbance, COD, TOC and TIC.
Article
The environmental problems associated with textile activities are represented mainly by the extensive use of organic dyes. A great number of these compounds are recalcitrant and shown carcinogenic or mutagenic character. In this work three processes were studied for degradation of an anthraquinone dye (C.I. reactive blue-19). The ozonation process leads to complete decolorization with a very short reaction time; however, effective mineralization of the dye was not observed. The enzymatic process promotes quick decolorization of the dye; nevertheless, maximum decolorization degrees of about 30% are insignificant in relation to the decolorization degree achieved by the other processes. The best results were found for the photocatalytical process. The use of ZnO or TiO2 as photocatalysts, permits total decolorization and mineralization of the dye with reaction times of about 60 min.
Article
In the present study, electrochemical degradation experiments were conducted to degrade a textile dye namely Reactive Blue 19 (RB-19). A laboratory scale bench-top reactor was used to investigate the effect of various operating parameters using titanium based dimensionally stable anode (DSA). The oxidation of RB-19 takes place in the bulk solution with electrolytically generated chlorine/hypochlorite. Increasing the initial pH and increasing the reaction temperature decreases the de-colorization efficiency. At the same time, increasing the chloride concentration and increasing the current density showed an increase in the color removal. The complete removal of color was achieved within a short period of electrolysis for different concentrations of RB-19. However, the removal of chemical oxygen demand (COD) and total organic carbon (TOC) was 55.8% and 15.6%, respectively, for 400 mg/L RB-19 with 1.5 g/L sodium chloride concentration. The intermediate compounds formed during the degradation were identified using a gas chromatography coupled with mass spectrometry (GC/MS). In the present study, no chlorinated organic compounds were detected during the course of electrolysis. The major compounds identified were benzene, 2-hydroxy, 4,4-napthaquinoine (C.I. Natural orange 6), 1-aminoanthraquinone (C.I. Diazo fast red AL), benzyl alcohol, benzaldehyde, benzoic acid, phthalic anhydride, phthalide, phthaldehyde and 1,3-indanone.
Article
The sonolytic degradation of methyl tert-butyl ether (MTBE) has been investigated at ultrasonic frequency of 20 kHz. The observed pseudo-first-order rate constant decreased from 1.25 x 10(-4) to 5.32 x 10(-5) s(-1) as the concentration of MTBE increased from 2.84 x 10(-2) to 2.84 x 10(-1) mM. The rate of degradation of MTBE increased with the increase of the power density of ultrasonicator and also with the rise in reactor system temperature. In the presence of oxidising agent, potassium persulphate, the sonolytic rate of degradation of MTBE was accelerated substantially. Tert-butyl formate (TBF) and acetone were found to be the major intermediates of the degradation of MTBE. It is found that the ultrasound/Fe2+/H2O2 method is promising process for the degradation of MTBE. More than 95% degradation of MTBE (2.84 x 10(-2) mM) along with its intermediate products has been achieved during the coupled ultrasound/Fe2+/ H2O2 method. Hence, the coupled ultrasound/Fe2+/H2O2 may be a viable method for the degradation MTBE within a short period of time than the ultrasound irradiation process only. A kinetic model, based on the initial rates of degradation of MTBE and TBF, provides a good agreement with the experimental results.
Article
Reductive decolorization of two anthraquinone reactive dyes (Reactive Blue 4, RB4; Reactive Blue 19, RB19) under methanogenic conditions was performed using a mixed, methanogenic culture. Decolorization of the two anthraquinone dyes was investigated to evaluate the rate and extent of color removal as well as to assess possible toxic effects of the dyes and their decolorization product(s) on the methanogenic culture as a function of initial dye concentration ranging from 50 to 300 mg x L(-1). A dextrin/peptone mixture was used as the carbon and electron source. A high rate and extent of color removal was achieved ranging from 4.3 to 29.9 mg x L(-1)h(-1) and 73-91% for RB4, and 13.0-74.4 mg x L(-1)h(-1) and 90-95% for RB19. Initial RB4 concentrations up to 100 mg x L(-1) did not result in any significant inhibition. Both the 200 and 300 mg x L(-1) RB4-amended cultures, and all RB19-amended cultures resulted in severe inhibition of both acidogenesis and methanogenesis. Sequential dye addition at 300 mg x L(-1) for both RB4 and RB19 resulted in accumulation of volatile fatty acids (VFAs) and a very low methane production at the end of the first dye addition after 44 days of incubation. However, at the end of the second dye addition, after a relatively long incubation (384 days), recovery of methanogens in the RB4-amended culture was observed in contrast to the complete inhibition of methanogenesis in the RB19-amended culture. Therefore, RB19 resulted in a higher degree of inhibition of both acidogenesis and methanogenesis than RB4. Addition of dextrin/peptone to dye-inhibited cultures resulted in acidogenesis and a gradual recovery of methanogenesis (mainly aceticlastic methanogenesis) in the RB4-inhibited culture, and a slow recovery of acidogenesis but no recovery of methanogenesis in the RB19-inhibited culture. In contrast, addition of 80% H(2)-20% CO(2) gas to dye-inhibited cultures resulted in recovery of hydrogenotrophic methanogenesis in both the RB4- and RB19-inhibited cultures. In spite of the relatively severe inhibition of the two anthraquinone dyes on the mixed, methanogenic culture, a high extent of color removal was achieved.
Article
Comparative degradation of azo dyes by 520 kHz ultrasonic irradiation and its combinations with ozone and/or ultraviolet light (UV) was investigated using a probe dye C.I. Acid Orange 7. Operation parameters such as ultrasonic power density, ozone flow, UV intensity, and type and injection mode of the bubbling gas were optimized based on the rate of absorption decay in the visible and UV bands as estimated by regression analysis of absorption-time data. At equivalent initial dye concentrations and contact times, individual effects of UV irradiation, ultrasound and ozone were "no effect", "bleaching", and "bleaching/organic carbon degradation", respectively. UV irradiation, however, was found to induce a catalytic effect when applied in combination with either ultrasound or ozone schemes; and the overall degradation process was most rapid under simultaneous operation of the three in the presence of a continuous flow of a gas mixture made of argon and oxygen. The synergy observed in combined schemes was attributed to enhanced ozone diffusion by mechanical effects of ultrasound, and the photolysis of ultrasound-generated H(2)O(2) to produce hydroxyl radicals.
Article
We studied in batch assays the transformation and toxicity of anthraquinone dyes during incubations with anaerobic granular sludge under mesophilic (30 degrees C) and thermophilic (55 degrees C) conditions. Additionally, the electron shuttling capacity of the redox mediator anthraquinone-2-sulfonic acid (AQS) and subsequent increase on decolourisation rates was investigated on anthraquinone dyes. Compared with incubations at 30 degrees C, serum bottles at 55 degrees C presented distinctly higher decolourisation rates not only with an industrial wastewater containing anthraquinone dyes, but also with model compounds. Compared with batch assays at 30 degrees C, the first-order rate constant "k" of the Reactive Blue 5 (RB5) was enhanced 11-fold and 6-fold for bottles at 55 degrees C supplemented and free of AQS, respectively. However, the anthraquinone dye Reactive Blue 19 (RB19) demonstrated a very strong toxic effect on volatile fatty acids (VFA) degradation and methanogenesis at both 30 degrees C and 55 degrees C. The apparent inhibitory concentrations of RB19 exerting 50% reduction in methanogenic activity (IC50-value) were 55 mg l(-1) at 30 degrees C and 45 mg l(-1) at 55 degrees C. Further experiments at both temperatures revealed that RB19 was mainly toxic to methanogens, because the glucose oxidizers including acetogens, propionate-forming, butyrate-forming and ethanol-forming microorganisms were not affected by the dye toxicity.
Article
The three most commonly used dyestuffs in textile industry are reactive, acid, and dispersed dyes. One dye from each group, C.I. Reactive Blue-19, C.I. Acid Red-266, and C.I. Disperse Yellow-218 was chosen to study the feasibility of coagulation for color removal. The dyes used in these experiments were chosen to represent the two major structural features: anthraquinone and azo dyes. Reactive Blue is an anthraquinone-based dye, and Acid Red and Disperse Yellow represent azo-based dyes. As there is no standard method to measure the color intensity, a Hach spectrophotometer was used to measure the absorbance before and after the dye solution was treated. Removal efficiencies on these dyes were obtained by measuring absorbance of a sample at 592 nm for Reactive Blue, 498 nm for Acid Red, and 428 nm for Disperse Yellow. Aluminum and ferric coagulants were produced in a parallel-plate electrochemical reactor by anodic dissolution. Removal efficiencies of more than 98%, in terms of absorbance, were observed in laboratory conditions. Removal was found highly dependent upon NaCl concentration, applied voltage, current density, and pH. The NaCl in the solution effectively reduced the power consumption and promoted the coagulant generation by depasivating the Al-water and Fe-water electrochemical systems. The processes were determined to be highly NaCl dependent. A mechanism was proposed for the corresponding liquid phase chemistry.
Article
This study investigated the decolorization of the Reactive Red 2 in water using advanced oxidation processes (AOPs): UV/TiO2, UV/SnO2, UV/TiO2+SnO2, O3, O3+MnO2, UV/O3 and UV/O3+TiO2+SnO2. Kinetic analyses indicated that the decolorization rates of Reactive Red 2 could be approximated as pseudo-first-order kinetics for both homogeneous and heterogeneous systems. The decolorization rate at pH 7 exceeded pH 4 and 10 in UV/TiO2 and UV/TiO2+SnO2 systems, respectively. However, the rate constants in the systems (including O3) demonstrated the order of pH 10>pH 7>pH 4. The UV/TiO2+SnO2 and O3+MnO2 systems exhibited a greater decolorization rate than the UV/TiO2 and O3 systems, respectively. Additionally, the promotion of rate depended on pH. The variation of dye concentration influenced the decolorization efficiency of heterogeneous systems more significant than homogeneous systems. Experimental results verified that decolorization and desulfuration occurred at nearly the same rate. Moreover, the decolorization rate constants at pH 7 in various systems followed the order of UV/O3 > or = O3+MnO2 > or = UV/O3+TiO2+SnO2 > O3 > UV/TiO2+SnO2 > or = UV/TiO2 > UV/SnO2.
Article
The utilization of modified bentonite with a cationic surfactant (dodecyltrimethylammonium (DTMA) bromide) as an adsorbent was successfully carried out to remove a synthetic textile dye (Reactive Blue 19 (RB19)) by adsorption, from aqueous solutions. Batch studies were carried out to address various experimental parameters such as pH, contact time and temperature. The surface modification of bentonite with a surfactant was examined using the FTIR spectroscopic technique and elemental analysis. Effective pH for the adsorption of RB19 onto DTMA-bentonite was around 1.5. The Langmuir isotherm model was found to be the best to represent the equilibrium with experimental data. The maximum adsorption capacity (q(max)) has been found to be 3.30x10(-4)molg(-1) or 206.58mgg(-1). The thermodynamic study indicated that the adsorption of RB19 onto DTMA-bentonite was favored with the negative Gibbs free energy values. The pseudo-second-order rate equation was able to provide the best description of adsorption kinetics and the intraparticle diffusion model was also applicable up to 40min for the adsorption of RB19 onto DTMA-bentonite.
Article
The decolorization and degradation of CI Direct Red 23, which is suspected to be carcinogenic, were investigated using ozonation combined with sonolysis. The results showed that the combination of ozonation and sonolysis was a highly effective way to remove color from waste water. The operational parameters, namely concentration of the dye, pH, ozone dose and ultrasonic density, were investigated during the process. The decolorization of the dye followed pseudo-first-order kinetics. Increasing the initial concentration of Direct Red 23 led to a decreasing rate constant. The optimum pH for the reaction was 8.0, and both lower and higher pH decreased the removal rate. The effect of the ozone dose on the dye decolorization was much greater than that of the sonolysis density. Intermediates such as naphthalene-2-sulfonic acid, 1-naphthol, urea and acetamide were detected by gas chromatography coupled with mass spectrometry in the absence of pH buffer, while nitrate and sulfate ions and formic, acetic and oxalic acids were detected by ion chromatography. A tentative degradation pathway was proposed without any further quantitative analyses. During the degradation, all nitrogen atoms and phenyl groups of Direct Red 23 were degraded into urea, nitrate ion, nitrogen and formic, acetic and oxalic acids, etc.
Article
The electrochemical performance of pure Ti-Pt/beta-PbO2 electrodes, or doped with Fe and F (together or separately), in the oxidation of simulated wastewaters containing the Blue Reactive 19 dye (BR-19), using a filter-press reactor, was investigated and then compared with that of a boron-doped diamond electrode supported on a niobium substrate (Nb/BDD). The electrooxidation of the dye simulated wastewater (volume of 0.1 l, with a BR-19 initial concentration of 25 mg l(-1)) was carried out under the following conditions: current density of 50 mA cm(-2), volume flow rate of 2.4 l h(-1), temperature of 25 degrees C and electrode area of 5 cm2. The performances of the electrodes in the dye decolorization were quite similar, achieving 100% decolorization, and in some cases 90% decolorization was achieved by applying only ca. 0.3 A h l(-1) (8 min of electrolysis). The reduction of the simulated wastewater organic load, monitored by its total organic carbon content (TOC), was greater for the Ti-Pt/beta-PbO2-Fe,F electrode obtained from an electrodeposition bath containing 1 mM Fe3+ and 30 mM F-. In this case, after 2 h of electrolysis the obtained TOC reduction was 95%, while for the pure beta-PbO2 and the Nb/BDD electrodes the reductions were 84% and 82%, respectively.
Article
The operational parameters and mechanism of mineralization of C.I. Reactive Yellow 84 (RY84), one of the azo dyes, in aqueous solution were investigated using sonolytic ozonation (US/O(3) oxidation). Of the pseudo-first-order degradation rate constants of TOC reduction, 9.0 x 10(-4), 7.3 x 10(-3) and 1.8 x 10(-2)min(-1) were observed with US, O3, and a combination of US and O3, respectively. These results illustrate that ozonation combined with sonolysis for removal of TOC is more efficient than ozonation alone or ultrasonic irradiation alone without considering the operating costs. With the initial pH value at 10.0, the ozone dose at 4.5 g h(-1), the energy density of ultrasound at 176 W l(-1), and the initial concentration of RY84 at 100 mg l(-1), the extent of mineralization measured as TOC loss was maximized. The variation of the concentrations of related ions (oxalate, formate, acetate, NO3(-), NO2(-), NH4(+), Cl(-), and SO4(2-)) during the reaction process was monitored. Other organic intermediates detected by GC/MS were N-methyleneaniline, phthalic acid, 4-hydroxyphthalic acid, isocyanatobenzene, aniline, 4-iminocyclohexa-2,5-dien-1-one, butene diacid and urea. Based on these findings, a tentative degradation pathway was proposed.
On the performance of Fe and Fe, F doped Ti–Pt
  • L S Andrade
  • L A M Ruotolo
  • R C Rocha-Filho
  • N Bocchi
  • S R Biaggio
  • J Iniesta
  • V García-Garcia
L.S. Andrade, L.A.M. Ruotolo, R.C. Rocha-Filho, N. Bocchi, S.R. Biaggio, J. Iniesta, V. García-Garcia, V. Montiel, On the performance of Fe and Fe, F doped Ti–Pt/PbO2 electrodes in the electrooxidation of the Blue Reactive 19 dye in simulated textile wastewater, Chemosphere 66 (2007) 2035–2043.