Modified Fenton Oxidation

The increasing presence of organic pollutants in wastewater has become a major concern, primarily due to rapid population growth and ongoing technological advancements that deplete water resources. Consequently, water bodies are becoming increasingly polluted, posing significant risks to the environment. Therefore, it is essential to develop advanced wastewater treatment technologies to ensure clean water and sanitation for both present and future generations. Ultrasound-based oxidants (US/oxidants) are emerging as effective technologies for removing pollutants from water and wastewater. This review compiles recent progress in the use of US/oxidants, including US/persulfates, US/hydrogen peroxide, US/ozone, US/chlorine, US/permanganate, US/periodate, and US/peracetic acid, for the removal of various organic pollutants. It provides comprehensive explanations of the mechanisms and reactions involved in each process, outlines the production of reactive agents, and compares the applications of each process for the degradation and treatment of pollutants. Furthermore, the review evaluates the performance of these processes on real wastewater, discusses their advantages and limitations, and highlights the challenges and future prospects, offering valuable insights into the practical application of US/oxidants for pollutant remediation in wastewater.

The textile industry produces large amounts of wastewater during all phases of textile production and finishing. Major pollutants in textile wastewaters are high suspended solids, chemical oxygen demand, heat, color, acidity, and other soluble substances .Textile washing operations are the most water intensive processes in textile production. Wastewater from textile washing contains high quantities of chemical residues, which originate from previous textile processing steps, including dyes. The raw materials for the manufactures of dyes are mainly aromatic hydrocarbons . The removal of color in textile industry and dyestuff manufacturing industry wastewaters represents a major environmental concern . Ozone is a powerful oxidizing agent. The reactions of ozone with organic compounds in aqueous media have been under investigation by different authors. These reactions are complex with many intermediates . Chemical oxidation is frequently another tool in wastewater treatment; chemical o...

Azo dyes account for about 60-70% of all dyes in textile, food, pharmaceutical, leather, cosmetics and paper industries and are the most common synthetic colorants released into the environment, causing undesirable colouring of surface waters, as well as toxicity and mutagenicity problems. Their removal is a major concern when treating dyeing-processing wastewaters. Under anaerobic conditions, azo dyes are non-specifically reduced, a fortuitous but often slow process. Acceleration can be achieved by using electron-shuttling compounds that speed up the reaction by acting as redox mediators. Activated carbon (AC) has been shown a feasible redox mediator. Moreover, it was shown that the surface chemistry of AC plays a key role in dye adsorption performance. In this study, the effect of modified AC on anaerobic chemical dye reduction was assayed. The surface chemistry of AC was selectively modified, without changing significantly its textural properties, by means of chemical oxidation using 6 M HNO 3 (AC with acidic surface properties) and thermal treatments (900 ºC) under a flow of H 2 or N 2 (AC with basic surface properties). Oxidation with 5% O 2 (in N 2 ) was also performed leading not only to surface chemistry changes (acidic properties), but also in the textural properties. Characterization of AC samples was also done. Four azo dyes from different classes, Acid Orange 7, Reactive Red 2, Mordant Yellow 10 and Direct Blue 71, were tested and at different pH values, 5, 7 and 9. Batch experiments in the presence of low amounts of AC, demonstrated an increase of the firstorder reduction rate constants for all the studied azo dyes as compared with assays without AC. The reduction of AO7 and MY10 with all the treated AC was highly dependent on the pH, with optimum rates at pH 5 and 7, respectively. Higher rates of RR2 and DB71 reduction were obtained at pH 5. The best decolourisation results were obtained with basic AC samples (AC_N 2 and AC_H 2 ). Comparing the rates of single dyes, MY10 was the faster reduced (12 ± 2.3 d -1 ) and RR2 the slowest (1.3 ± 0.1 d -1 ). In fact, MY10 was almost completely decolourised in 1 day. Colour removal of 80% was obtained for DB71 at a rate of 5.6 ± 0.3 d -1 . AO7 and RR2 were the most resistant to degradation (~ 60 %).

The effective treatment of dye-laden industrial effluents remains a critical challenge in environmental engineering. This study introduces a novel hybrid system integrating ultrasound (US) and nanofiltration (NF) technologies for the removal of Remazol Brilliant Blue Reactive (RBBR) dye from aqueous solutions. RBBR, a widely used textile dye, poses significant environmental and health risks due to its persistence and toxicity. For the first time, the influence of pH on the performance of a hybrid US-NF system for RBBR removal, including byproduct formation and membrane fouling was systematically investigated. Initially, the US and NF processes were optimized independently by systematically varying key parameters such as US frequency, exposure time, membrane pressure, and solution pH. Ultrasonic treatment at 575 kHz resulted in 79 % reduction in absorbance and 58 % total organic carbon (TOC) removal at pH 3 after 90 min, indicating partial oxidation of the dye. NF alone consistently removed over 99 % of the dye across all tested pH values, though a flux decline of 16 % was observed at pH 3 due to fouling. The hybrid US-NF system maintained over 99 % dye rejection while completely eliminating flux decline at an optimal pH of 3, significantly outperforming the standalone NF process. Degradation by-products were confirmed via mass spectrometry and Fourier-transform infrared spectroscopy, highlighting the complementary role of NF in removing potential intermediates. These results demonstrate the potential of US-NF coupling as a robust and sustainable approach for advanced treatment of dye-contaminated wastewater, contributing to the development of cleaner industrial processes and improved water reuse practices.

This article describes the potential of KMnO 4 for oxidation of the thiazine dye (Toluidine blue TB) in an acidic medium. The effect of different operational parameters like initial concentration of dye, potassium permanganate, pH, ionic strength, catalyst, acids and temperature were investigated spectrophotometrically at l max = 613 nm. The results showed a complete removal of the TB with mineralization of the dye solution. Smooth and complete decoloration was observed in the presence of monobasic acid (HCl) as compared to the H 2 SO 4 where little color removal was observed. Pb was found to be an effective catalyst in oxidation for complete and fast decolorization with mineralization. No significant change at elevated temperatures showed that an intermediate complex degraded with slight change in the temperature. UV/ visible spectrophotometry and GC mass analysis showed an intermediate activated complex demethylated sulophooxide of TB which later on degraded into smaller fragments.

BACKGROUND: Nitrogen doped titanium dioxide (N-TiO 2), iron doped titanium dioxide (Fe-TiO 2), and undoped titanium dioxide (TiO 2) nanocatalysts were synthesized using sol-gel method aided with ultrasound (US). The effects of duty cycle, US-power, and US irradiation time on catalyst characteristics were investigated so as to establish the best synthesis conditions. RESULTS: The optimum parameters for minimum mean size of catalyst particles were 60% duty cycle, 100 W power, and 20 min as irradiation time. X-Ray diffraction (XRD) analysis revealed that the primary phase of all nanocatalysts was anatase with crystallite size as 46.29 nm, 54.32 nm, and 56.17 nm for N-TiO 2 , Fe-TiO 2 , and undoped TiO 2 , respectively. Field electron scanning electron microscopy (FE-SEM) images confirmed that N-TiO 2 is a mixture of TiO 2 microspheres and rice-like structures whereas Fe-TiO 2 and undoped TiO 2 were spherical. X-ray photoelectron spectroscopy (XPS) study showed that both N-TiO 2 and Fe-TiO 2 exhibited minor shifts to lower binding energies when compared to the spectra of undoped TiO 2. The application studies for obtained catalysts using simple ultrasonic horn and disc horn coupled with oxidants revealed best results (51.67% reduction in COD) using disc horn for N-TiO 2 catalyst obtained using ultrasound at pH of 12 and addition of a 20 mL per L-1 dose of H 2 O 2. CONCLUSION: Doping TiO 2 with metal and non-metal ions coupled with using ultrasound in synthesis improved the catalytic activity with maximum COD reduction of commercial effluent obtained for disk horn + N-TiO 2 + H 2 O 2 based approach.

Microbial fuel cells (MFCs) represent a transformative technology at the intersection of wastewater treatment and renewable energy, offering a sustainable pathway to achieve Sustainable Development Goals 6 (clean water and sanitation) and 7 (affordable and clean energy). Despite significant advancements, scaling up MFCs for industrial application remains challenging due to efficiency limitations, biofilm stability and material performance. This study employs the TRIZ patent literature review (TRIZ-PLR) methodology to systematically analyze 1513 active patents related to MFC innovations, identifying key technological contradictions and evolutionary trends. The research highlights advancements in nanomaterials, multichamber reactor configurations and optimized flow dynamics as critical enablers for enhancing power output and microbial activity. Unlike conventional reviews, this study provides a structured, patent-based innovation roadmap, offering actionable insights for researchers and industry stakeholders. By bridging academic research with industrial applicability, our findings inform scalable MFC integration into circular economy frameworks, reinforcing their potential for sustainable energy production and waste management.

Dyes are those synthetic and natural compounds which applied in form of aqueous based solutions with many additives to strong attachment of dye molecule with a fabric for persistence the colour on it while pigments are usually insoluble. There are various methods of dye all over the world for dye fabrications. Dyes fabrication processes require thousands liters of water for coloring materials which need very small amount of it and remaining water discharged as a dye waste water and become hazardous to ecology. As an effluent from textile and printing industries having remaining dyes and several additives it become one of the central sources with severe pollution complications worldwide and hard to treat by conventional Chemical/Biological processes. This complex nature of dye wastewater can be converted into less harmless/useful by products along with conventional biological treatment, chemical treatment or set of chemical treatments like Advanced Oxidation processes are used. This ...

Lawrence K. Wang, Mu-Hao Sung Wang, Yung-Tse Hung (2021). Integrated Natural Resources Research, Springer Cham, NY, USA; 651 pages, ISBN:  978-3-030-61001-2; https://doi.org/10.1007/978-3-030-61002-9    ....    ABSTRACT:  The book will be useful to environmental resources engineers, researchers, water treatment plant managers, chemical engineers, industrial plant managers, and environmental conservation agencies. This book includes 12 chapters: (1) Fenton Oxidation and Biological Activated Carbon Treatment for Recycling Biotreated Coking Plant Wastewater; (2) Composting for Food Processing Wastes; (3) Treatment of Wastewaters from Chemical Industries; (4) Agricultural Waste as a Low-Cost Adsorbent; (5) Waste Vegetable Oils, Fats, and Cooking Oils in Biodiesel Production;  (6) Physicochemical Treatment Consisting of Chemical Coagulation, Precipitation, Sedimentation, and Flotation; (7) Water Quality Control of Tidal Rivers and Estuaries; (8) First Wave of Flotation Technology Evolution: Once the World’s Largest DAF-Filtration Plant and Its Hydroelectric Facility;  (9) Cationic Surfactant Analysis with Good Laboratory Practice and Waste Management; (10) Treatment of Laundry Wastewater by Physicochemical and Flotation Processes;  (11) Book Reviews: Natural Resources; and (12) Glossary of Water Quality, Treatment, and Recovery.

The aqueous degradation of Reactive Yellow 84 (RY84) by potassium peroxydisulfate (K 2 S 2 O 8) has been studied in laboratory scale experiments. The effect of the initial concentrations of potassium peroxydisulfate and RY84, pH and temperature on RY84 degradation were also examined. Experimental data were analyzed using first and second-order kinetics. The degradation kinetics of RY84 of the potassium peroxydisulfate process followed the second-order reaction kinetics. These rate constants have an extreme values similar to of 9.493 mM À1 min À1 at a peroxydisulfate dose of 4 mmol/L. Thermodynamic parameters such as activation (Ea) and Gibbs free energy (DG°) were also evaluated. The negative value of DG o and E a shows the spontaneous reaction natural conditions and exothermic nature.

A nanocrystalline anatase hydrate (Titanhydrat-0, TH) is a highly efficient catalyst for low intensity sonochemical degradation of 4-chlorophenol (4-CP). The initial disappearance rate of 4-CP increases by a factor of 95 under the TH dosage of 0.5 g dm À3. After 120 min of ultrasonic irradiation 63% of 4-CP is completely mineralized under the TH dosage of 0.5 g dm À3. However, in homogeneous sonochemical degradation, no mineralization at all occurs. Moreover, we deduce that the process of sonochemical mineralization mainly occurs at the interface region of TH. The process of sonocatalytic degradation is simple and inexpensive, and appears to be a potentially powerful method of remediation of contaminants in water.

Neutral Red was subjected to two different oxidative processes, namely the photo-oxidative process and the Fenton process. The dye was found to undergo substantial and rapid decoloration by both the methods. Conditions were optimized in both the sets of experiments to achieve the most efficient dye decoloration. Additionally the effects of added anions on dye decoloration were examined and it was found that in both cases, the chloride ions caused a significant decrease in the decoloration rate. The kinetics data in both the cases fitted well to the first-order equation. A comparison of the effects of various anions on the decoloration rate revealed dramatic differences in apparent rate constant of decoloration of the dye especially in the presence of phosphate ions. Additionally the Fenton process was found to be more efficient in decolorizing the dye as compared to the photo-oxidative process.

The degradation of Reactive Black 5 (KN-B) in water using double-dielectric barrier discharge (DDBD) was studied. Experimental results showed that the KN-B degradation rate increased as the initial pH decreased. Low concentrations of Fe2+ enhanced the degradation, whereas high concentrations of Fe2+ hindered the degradation. The results showed that DDBD did not noticeably reduce total organic carbon but did reduce the pH value and improve the biodegradability of the solution significantly. Furthermore, the UV–Vis spectra of the dye showed that the chromophore group was damaged and that the solution was decolorized after the 10-min degradation process.

Highlights: •O3-based AOPs constitutes a good process to treat textile wastewater. •The wastewater matrix caused lack of summary effect of O3, UV and H2O2 within AOPs. •Ozone treatment was not influenced by textile auxiliaries. •Textile wastewater treated by AOPs can be reused as a brine for the next dyeing.

Wastewater-based microbial fuel cell is a promising green technology that can potentially be used to treat recalcitrant wastewater such as textile wastewater through in situ Fenton oxidation while generating net positive energy. One of the main features of this technology is the use of membranes for isolating the cathode chamber for in situ H 2 O 2 production (thus in situ Fenton oxidation). The challenges in this technology include membrane fouling and resistance, pH splitting, oxygen diffusion, substrate crossovers, effect of Fenton's reagents and high cost of commercially available membranes. Therefore, this paper critically analyzes each challenge in detail to access their direct or indirect effects on the overall performance. Exploration of new materials and modifications of existing materials has produced cost-efficient and reliable membranes. However, their application in in situ Fenton oxidation has not been demonstrated. It is concluded that the use of membranes with high hydrophilicity, small pore size and materials enriched with sulfonated groups is suitable for in situ H 2 O 2 production in the cathode chamber. Moreover, use of cleaning agents such as H 2 O 2 or H 2 SO 4 recovers the membrane performance for in situ H 2 O 2 production. Thus, it offers a green technology because in situ H 2 O 2 can be used for membrane cleaning and energy produced can be used for aeration of the cathode chamber.

In the present study, a comparison of central composite design (CCD) and Taguchi method was established for Fenton oxidation.Dyeini, Dye : Fe+2, H2O2 : Fe+2, and pH were identified control variables while COD and decolorization efficiency were selected responses.L9orthogonal array and face-centered CCD were used for the experimental design. Maximum 99% decolorization and 80% COD removal efficiency were obtained under optimum conditions.Rsquared values of 0.97 and 0.95 for CCD and Taguchi method, respectively, indicate that both models are statistically significant and are in well agreement with each other. Furthermore, Prob >Fless than 0.0500 and ANOVA results indicate the good fitting of selected model with experimental results. Nevertheless, possibility of ranking of input variables in terms of percent contribution to the response value has made Taguchi method a suitable approach for scrutinizing the operating parameters. For present case, pH with percent contribution of 87.62%...

Application of the Fenton process for textile wastewater treatment is limited due to high treatment cost, substantially contributed by the un‐availability of cheap hydrogen peroxide. Therefore, alternative methods for hydrogen peroxide production are in demand. One such option is in situ hydrogen peroxide production using a wastewater based microbial fuel cell (WBMFC). However, not much have been published regarding in situ production of hydrogen peroxide for textile wastewater treatment in a WBMFC. Therefore, in this work the concept, advantages, challenges and prospects of using WBMFC to treat textile wastewater by simultaneously producing hydrogen peroxide (hence in situ hydrogen peroxide) and power are reviewed. The concept of WBMFC is the reduction of oxygen in the presence of electrons and protons from the anode chamber to produce hydrogen peroxide with simultaneous power production. This review confirms that use of dual chambers, proton exchange membrane, domestic or municipa...

The main objective of this work was to study the degradation of Acid Orange 7 (AO7) dye in aqueous solution by hydrogen peroxide using HFe 2.5 P 2 W 18 O 62 23.H 2 O as a catalyst. HFe 2.5 P 2 W 18 O 62 23.H 2 O is a recyclable DAWSON-type heteropolyanion. Effects of various experimental parameters of the oxidation reaction of the dye were investigated. The studied parameters were the initial pH, the initial H 2 O 2 concentration, the catalyst mass, and the dye concentration. The optimum conditions had been determined, and it was found that efficiency of degradation obtained was about 100%. The optimal parameters were: initial pH 4; [H 2 O 2 ] 0 = 2 mM; catalyst mass 0.01 g; concentration of dye 30 mg/L. Infrared spectroscopy analysis of the HFe 2.5 P 2 W 18 O 62 23.H 2 O catalyst indicates that the catalyst showed good stability for degradation of AO7 even after second cycle.

The effectiveness of peroxymonocarbonate ( HCO 4 − ) on the degradation of Reactive Blue 19 (RB19) textile dye was investigated in this study. The formation kinetics of HCO 4 − produced in situ in a H 2 O 2 − HCO 3 − system was studied to control the experimental conditions for the investigation of RB19 degradation at mild conditions. The effects of metallic ion catalysts, the pH, the input HCO 3 − and Co2+ concentrations, and UV irradiation were studied. The obtained result showed that Co2+ ion gave the highest efficiency on accelerating the rate of RB19 degradation by the H2O2– HCO 3 − system. In the pH range of 7–10, the higher pH values resulted in faster dye degradation. The reaction orders of the RB19 degradation with respect to Co2+ and HCO3– were determined to be 1.2 and 1.7, respectively. The UV irradiation remarkably enhanced the radical formation in the oxidation system, which led to high degradation efficiencies. The COD, TOC removal, and HPLC results clearly revealed co...

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Abstract: The photocatalytic degradation of lissamine fast yellow has been carried out in the aqueous suspension of ZnO under artificial light. The effects of process parameters such as catalyst loading, H 2 O 2, FeCl 3, etc., on the extent of degradation have been studied. The ...

Microbial fuel cells (MFCs) are typically designed as a two-chamber system with the bacteria in the anode chamber separated from the cathode chamber by a polymeric proton exchange membrane (PEM). Most MFCs use aqueous cathodes where water is exposed to air to provide dissolved oxygen to electrode. To increase energy output and reduce the cost of Microbial Fuel Cells, charcoal electrode (locally prepared) at the composition of 2:1 charcoal/cement ratio was used. Ammonia fertilizer plant liquid effluent was used as the substrate, while the bacteria present in the wastewater were used as the biocatalyst. The cells were operated at room temperature with pH of 6.68. The anode and cathode chambers were kept under anaerobic and aerobic conditions respectively. The cell 3 setup with electrode area of 3.63×10-3 m 2 was observed to have the highest power density of 134.5455mW/m 2 and current density of 181.8182mA/m 2 while cell 4 setup with electrode area of 3.63×10-3 m 2 was observed to have the least power density of 108.9807mW/m 2 and current density of 126.7218mA/m 2 .

Advanced oxidation processes are eco-friendly methods of destroying organic pollutants by using semiconductor and visible light. Photocatalytic degradation of methylene violet has been investigated in aqueous heterogeneous suspension. The results indicated that potocatalytic reaction was enhanced in alkaline medium. The degradation of dye depends on several parameters such as initial concentration of the dye, catalyst loading, pH, electron acceptors and light intensity. COD removal was measured at regular intervals to quantify the mineralization of methylene violet. Sunlight has also been effectively used to degrade methylene violet.

The production of an efficient, reusable, stable and easily separable catalyst in the ozonation process through a reliable procedure is one of the essential requirements of the catalytic ozonation process (COP). In this study, the nano-MgO/CNT/Graphite composite was synthesized to use as a new catalyst in the COP. Synthesis of the nano-MgO/CNT/Graphite was carried out based on the extreme vertices mixture design (EVMD) using three components; MgO nanoparticles, carbon nanotubes (CNTs) and Graphite. Based on EVMD, 9 compositions were produced. For assessing the catalytic activity of synthesized compositions, pesticide manufacturing plant wastewater (PMPW) (initial COD=617 mg/L and TOC = 121) was treated in COP with new synthesized catalytic. The highest COD and TOC removal and destruction efficiencies were attained with composition C-9. The surface area of the optimum nano-MgO/CNT/Graphite was calculated to be had 221.631 m 2 g −1 and a high density of basic surface functional groups. Kinetics of PMPW oxidation indicated that the rate of COD and TOC removal efficiencies in the optimum nano-MgO/CNT/Graphite/O 3 process were 12.73 (13.24/1.04 mg COD/L.min) and 7.11 (1.44/0.2 mg TOC/L.min) times as high as those in the single ozonation (SOP), respectively. Clearly, the optimum nano-MgO/CNT/Graphite showed a significant ability in catalysis of the ozonation process of organic materials by means of increasing O 3 decomposition and % OH production. The synthesized optimum nano-MgO/ CNT/Graphite was reusable because of the stability and durability of the catalytic activities.

Photocatalytic degradation of pollutants under solar light irradiation is an economically viable process and a very promising clean wastewater treatment technology. The aim of this study is to evaluate photocatalytic degradation of Reactive Black 5 (RB5) under natural sunlight irradiation with TiO2 as photocatalyst. The effects of initial concentration of RB5, dosage of TiO2, with/without solar irradiation, with/without air sparging and pH solution were examined. The decolorization rate improved with a higher dosage of TiO2, with sunlight irradiation and air sparging, and under acidic solution. The photocatalytic process not only decolorized the RB5 but also mineralized the intermediate products completely.

In this investigation, nano ZnO was sonochemically synthesized by a novel method using a methionine precursor. A narrow size distribution (41-50 nm) of nano ZnO was achieved that was immobilized on perlite and applied as a catalyst in catalytic ozonation. The catalyst was characterized by fourier transform infrared spectroscopy, BET surface area, and field emission scanning electron microscope. The ozonation of recalcitrant Remazol black 5 (RB5) di-azo dye solution by means of the synthesized catalyst was investigated in a bubble column slurry reactor. The influence of pH values (7, 9, 11), catalyst dosage (8, 12, 15, 20 g L −1) and reaction time (10, 20, 30, 60 min) was investigated. Although the dye color was completely removed by single ozonation at a higher reaction time, the applied nanocatalyst improved the dye declorination kinetics. Also, the degradation of the hazardous aromatic fraction of the dye was enhanced five-times by catalytic ozonation at a low reaction time (10 min) and a neutral pH. The second-order kinetics was best fitted in terms of both RB5 color and its aromatic fraction removal. The total organic carbon analysis indicated a significant improvement in the mineralization of RB5 by catalytic ozonation using the nano-ZnO/perlite catalyst.

Methane is a widely available energy resource that can be obtained biologically as well as via natural gas. However, using methane as a fuel in low-temperature fuel cells has been a challenge due to the high thermodynamic stability of methane. In the current study, the feasibility of utilizing methane in a low-temperature microbial fuel cell (MFC) containing a pure culture of Methylococcus capsulatus without the addition of any supplementary electron mediators was studied. Two salt bridge fuel cell configurations were successfully operated. Electrochemical Impedance Spectroscopic studies showed that the biofilm on the anode took approximately one day to stabilize and continued to operate at full power for 7 test days. This work demonstrates the possibility of generating electricity using methane as the sole carbon source at room temperature with M. capsulatus pure culture as a direct electron-transporting MFC biocatalyst.

In this investigation, nano ZnO was sonochemically synthesized by a novel method using a methionine precursor. A narrow size distribution (41-50 nm) of nano ZnO was achieved that was immobilized on perlite and applied as a catalyst in catalytic ozonation. The catalyst was characterized by fourier transform infrared spectroscopy, BET surface area, and field emission scanning electron microscope. The ozonation of recalcitrant Remazol black 5 (RB5) di-azo dye solution by means of the synthesized catalyst was investigated in a bubble column slurry reactor. The influence of pH values (7, 9, 11), catalyst dosage (8, 12, 15, 20 g L −1) and reaction time (10, 20, 30, 60 min) was investigated. Although the dye color was completely removed by single ozonation at a higher reaction time, the applied nanocatalyst improved the dye declorination kinetics. Also, the degradation of the hazardous aromatic fraction of the dye was enhanced five-times by catalytic ozonation at a low reaction time (10 min) and a neutral pH. The second-order kinetics was best fitted in terms of both RB5 color and its aromatic fraction removal. The total organic carbon analysis indicated a significant improvement in the mineralization of RB5 by catalytic ozonation using the nano-ZnO/perlite catalyst.

In this investigation, nano ZnO was sonochemically synthesized by a novel method using a methionine precursor. A narrow size distribution (41-50 nm) of nano ZnO was achieved that was immobilized on perlite and applied as a catalyst in catalytic ozonation. The catalyst was characterized by fourier transform infrared spectroscopy, BET surface area, and field emission scanning electron microscope. The ozonation of recalcitrant Remazol black 5 (RB5) di-azo dye solution by means of the synthesized catalyst was investigated in a bubble column slurry reactor. The influence of pH values (7, 9, 11), catalyst dosage (8, 12, 15, 20 g L −1) and reaction time (10, 20, 30, 60 min) was investigated. Although the dye color was completely removed by single ozonation at a higher reaction time, the applied nanocatalyst improved the dye declorination kinetics. Also, the degradation of the hazardous aromatic fraction of the dye was enhanced five-times by catalytic ozonation at a low reaction time (10 min) and a neutral pH. The second-order kinetics was best fitted in terms of both RB5 color and its aromatic fraction removal. The total organic carbon analysis indicated a significant improvement in the mineralization of RB5 by catalytic ozonation using the nano-ZnO/perlite catalyst.

Wastewater from the textile industry containing a high concentration of organic and inorganic chemicals has strong color and residual chemical oxygen demand (COD). Therefore, advanced oxidation processes (AOPs) are very good candidates to treat textile industry wastewater. In this study, we investigated the effect of different types of AOPs supported with hydrogen peroxide (H 2 O 2) for the treatment of viscose fibers dyeing wastewater. Fenton, photo-Fenton, and Fenton-supported subcritical water oxidation (FSWO) processes were chosen as AOPs to compare the treatment efficiency of viscose fibers dyeing wastewater. The effects of solution pH, Fe 2þ concentration, and H 2 O 2 concentration on the treatment of viscose fibers dyeing wastewater were tested. The maximum color and COD removal efficiency was obtained corresponding to pH 2.5 for all oxidation methods when methylene blue (MB) dye solution was used. However, the maximum efficiencies were obtained at pH 3.0 for real textile wastewater decolorization. The MB dye removal efficiency was increased to 97.22, 100, and 100% for Fenton, photo-Fenton, and FSWO processes, respectively, when the addition of H 2 O 2 concentration was adjusted to 125 mg/L. However, the maximum color removal efficiencies of viscose fibers dyeing wastewater were obtained 56.94, 61.26, 64.11% for Fenton, photo-Fenton, FSWO processes, respectively. As a result, the FSWO showed maximum color removal efficiencies.

In this study, the photo‐Fenton process was used to identify degradation conditions of Reactive Blue 19 (RB19) and Reactive Red 21 (RR21). The effects of pH, initial H2O2 and FeSO4 concentrations, time, and UV light intensity in determining the degradation rate were studied. The optimal conditions for the degradation of 0.156 mmol L−1 RB19 and 0.036 mmol L−1 RR21 in water were found to be: pH 4, 0.1 mL 30% H2O2 for RB19 and RR21, 0.2 mL 0.5% FeSO4 for RB19 and 0.1 mL 0.5% FeSO4 for RR21, 20 mL volume, and a temperature of 20°C. Optimal conditions were applied to synthetic dye wastewater using small amounts of H2O2 in 1 L for degradation. The degree of degradation efficiency of synthetic wastewater by the photo‐Fenton process was found to be >95% within 10 min.

The photocatalytic performance of copper ferrite graphene oxide catalyst, CFXGO (CF: Copper ferrite, CuFe 2 O 4 ; GO: Graphene oxide; X: GO weight percentage) was tested for photo Fenton-like oxidation of Reactive Black 5 by using UV light irradiation. The effect of the graphene oxide content in the catalyst structure on dye removal efficiency was tested by comparing the performances of the catalysts with different weight ratios of graphene oxide varying between 5 and 90%. The catalysts were characterized by Scanning Electron Microscopy, X-Ray Diffraction, Brunauer-Emmett-Teller method, and, Vibrating Sample Magnetometer. The influences of catalyst loading, initial pH, and, the H 2 O 2 concentration were investigated in the presence of CF90GO catalyst, which has 90% graphene oxide content. According to the parametric studies, 98.2% decolorization and 82.8% TOC removal efficiencies were achieved in 2 h for the treatment of 50 mg/L RB5 solutions when the catalyst loading, the initial pH, and, the initial hydrogen peroxide concentration were 0.275 g/L, 7, and, 5.5 mM, respectively.

Reactive Black 5 was effectively degraded by the CWAO using LaNiO 3 catalyst. The most suitable reaction conditions were 1 g/L of LaNiO 3 , 50 C, 1 atm, and pH ¼ 3. 65.4% degradation and 89.6% decolorization efficiencies were achieved. The toxicity of the dye solution was reduced remarkably after the treatment.

Several processes have been used for dye and chemical oxygen demand (COD) removal from wastewater. Comparision of these methods are important in terms of efficiency and energy consumption. In recent years, advanced oxidation processes (AOPs) and electrocoagulation (EC) are the best methods for industrial dyeing wastewater treatment. In this study, comparision of energy consumption related to EC and photocatalytic process has been investigated. Effect of operational parameters on efficieny of both methods were studied. Effective parameters in EC treatment were initial pH, current density and distance between electrodes. In the photocatalytic process initial pH, photocatalyst concentration and aeration are effective parameters. Decolorization, COD removal, and energy consumption are as responses. Under the optimum conditions, decolorization and COD removal for EC and photocatalytic process were 85.57 and 34.48%, and 81.39 and 67%, respectively. Considering the same time for both metho...

h i g h l i g h t s Investigation of synergistic effects of AOPs for H 2 production and wastewater treatment processes. TiO 2 NPs utilization in combination with Fenton reactions for wastewater treatment. Wastewater treatment systems with simultaneous hydrogen production.

Nowadays, leaving industrial wastewater into receiving environment causes serious environmental problems. In this study, experimental studies on color and chemical oxygen demand (COD) removal of paper industrial wastewater were carried out. In this context, heterogeneous Fenton and photocatalytic oxidation processes were applied and removal efficiencies were compared. The Fe(III)/MnO2 catalyst containing 8% w/w of iron ion was synthesized to be used in experimental studies. The effects of parameters such as pH, catalyst amount, hydrogen peroxide concentration and reaction time were investigated. At the end of the experimental studies, 90% color and 55% COD removal efficiencies were obtained in heterogeneous Fenton process after 120 minutes reaction time under optimum conditions. After 60 minutes reaction time under the same optimum conditions, 97% color and 91% COD removal efficiencies were achieved in photocatalytic oxidation process.

The objective of this study was to investigate mineralization of hazardous water soluble azo dye Acid Orange 7 (AO7) under photocatalytic process. In this experiment, sunlight was used as the source for UV irradiation and titanium dioxide, TiO 2 as catalyst. The eff ects of some process variables on decolorization such as amount of TiO 2 , azo dye concentration and dosage of hydrogen peroxide (H 2 O 2) were examined. TiO 2-based photocatalytic degradation is an eff ective, economic and faster mode of removing azo dye AO7 from aqueous solution. The presence of sunlight enhanced the decolorization rate of AO7 and mineralized the intermediate products completely. The mineralization of AO7 was supported by the UV-Vis and ion chromatography analysis. The addition of proper amount of H 2 O 2 could optimize the decolorization rate of AO7. The photocatalytic degradation of AO7 followed fi rst-order kinetic model.

The treatment of textile wastewater (TWW) loaded with recalcitrant azo dyes in bioelectrochemical systems (BES) rather than in physicochemical processes is a low-cost and environmentally friendly process. The main objective of this study is to investigate the potential of different saline sediments collected from extreme Tunisian environments for the formation of bioanodes capable ofsimultaneous azo dyes degradation and electric current generation in synthetic (STWW) and real textile wastewaters (RTWW) characterized by a varied composition of azo dyes and a high salinity. The obtained bioanodes and anolytes were studied comparatively by electrochemical, microscopic, analytical, and molecular tools.Based on the UV–visible spectra analysis, the breakdown of the azo bond was confirmed. With RTWW, the BES achieved a chemical oxygen demand (COD) abatement rate of 85%with a current density of 2.5 A/m2. Microbial community analysis indicated that a diverse community of bacteria was active ...

Availability of clean water is of concern due to pollution and diminishing supply pollution. However, purification is possible depending on the incorporated contaminants. Domestic wastewater contains dissolved organic matter and its remediation can be done by oxidation. The best oxidation can be achieved by electron transfer the same way metabolic processes occur. This study exploited the use of a film of iron (III) doped titanium dioxide applied on an electrode which was found to be effective. Natural light conditions generated electrons that migrated through the electrode leaving behind holes which oxidized the contaminants as the excess electrons were discharged at the cathode after passing through the casted proton exchange membrane (PEM) separating the two half cells of the prepared reactor. This electrochemical method has the advantage in that the organic pollutants are oxidized to carbon dioxide with no secondary pollutants and the inorganic pollutants into insoluble matter. The assembled cell was applied to purify both synthetic and real water samples of green leafy vegetable solution from the kitchen by clarification. The clarification process was monitored by UV-Vis using distilled water as a reference to compare the light that transmitted through a sample. It was observed that the electro-oxidation process took place showing a high potential 105 mV within the first 150 min followed by degradation at a high rate. The oxidation of the organic matter was confirmed by UV-Vis analysis as well as by cyclic voltametric analysis of iron released into the solution of the synthetic samples. The electro chemical treatment of the water was then applied to purify real water samples made from a sample of 4.5 g minced of green vegetables dispersed in one liter of water (4.5 g/l). The green leafy coloured solution was clarified after 154 h of continuous oxidation. The degradation process was confirmed to be independent of intermediates or other species present in solution as it was of first order reaction kinetics. The electrochemical oxidation of organic matter in water using iron (III) doped titanium dioxide coated graphite electrode has potential application on the purification of water.

The novelty of this work lies in the use of a real textile wastewater (RTW), without a pretreatment, without additional carbon sources and undiluted, with coupling a photocatalysis by using an unprecedented composite for this application. The collected RTW containing the azo dye Direct Black 22 (205.15 mg L −1 TOC: 672.7 mg L −1), was treated with a bacterial consortium and after 96 h the sequential photocatalysis process was employed using ZnO/Polypyrrole during 60 min. The coupling of both treatment processes resulted in a total decolorization efficiency of 95.7 % and 99.8 % of TOC degradation (8.76 mg L −1 TOC: 1.33 mg L −1). Degradation product analysis was carried out by LC-MS/MS and a degradation pathway is proposed. The textile wastewater treatment proposed in this work is an attractive alternative and it is highly recommended to apply this system before the disposal of textile effluents in water bodies.

Decolorization of C.I. Acid Orange 7 (AO7) via TiO2-assisted photocatalysis under UV illumination in the presence of H2O2 has been investigated. The effect of pH on decolorization efficiency of AO7 was investigated in TiO2/UV/H2O2 process. The performance of TiO2/UV/H2O2 system was also evaluated by using synthetic dye-bath effluent of AO7. Solar driven TiO2 photocatalysis was found significantly efficient for the decolorization and degradation of AO7. The rates of decolorization and degradation of AO7 were found to follow pseudo-first order kinetics. The electrical energy consumption of decolorization of synthetic dye-bath effluent was found to be 4.1 times higher than that of AO7 solution. Similarly, the electrical energy consumption of degradation of synthetic dye-bath effluent was 2.2 times higher than that of AO7 solution under investigated conditions. Considering one order of magnitude reduction in AO7 concentration and COD value, the cost of electrical energy for decolorization and degradation of AO7 solution and synthetic dye-bath effluent of AO7 was calculated.

In this study sunlight and UV radiation were used to compare the efficiency of decolorization of textile wastewater containing brilliant reactive red dye K-2BP (λmax = 534 nm) by the advanced oxidation process (AOP) using (H2O2/sunlight, H2O2/UV, H2O2/TiO2/sunlight, and H2O2/TiO2/UV). The results studied the effect of solution pH, applied H2O2 concentration, TiO2 concentration (nanoparticle), and initial dye concentration were studied. The experimental results showed that decolorization percentage with H2O2/sunlight and TiO2/H2O2/sunlight under the following conditions:-reaction time 150 of minutes, [ 500 ppm] H2O2, [100 ppm] TiO2, pH=3, initial dye concentration =15 ppm and at ambient temperature were 95.7% and 98.42% respectively. For the same conditions using H2O2/UV, H2O2/TiO2 /UV, the percentage of decolorization were 97.85% and 96.33% respectively. The results also indicated that the sunlight is more economic and cost-effective than UV radiation.

The discharges of the wastewater from the textile industry generate a substantial quantity of effluents which can cause various environmental problems, if disposed of without any prior treatment. Therefore, the treatment of these textile effluents is necessary. The present study aims to investigate the removal efficiency of colors from wastewater containing mixed primary direct dyes and real textile industry wastewater using PDS (Peroxydisulfate)/Fe(II)/UV process. A simulated mixture, based on an industrial recipe and containing Reactive Yellow 17 (RY17), Reactive Red 120 (RR120), and Reactive Blue 19 (RB19), was investigated. The obtained results showed that the mineralization rate is around 96.1% for RY17, 99.2% for RR120, 100% for RB19 and 80% for their mixed during 2 h of the treatment. The degradation of real textile wastewater was about 66% under similar conditions. The evaluations showed that ~ 93.82 MAD/m 3 (~ 8.64 EURO/m 3) is needed to supply the operating cost. As a vital industrial criterion, it was estimated that the conditions of initial pH of 3, [PDS] = 1 mM and T = 25 °C the highest cost effective case of the process for degrading the mixed dyes. Phytotoxicity studies revealed that the degradation products of mixed dyes and textile effluent were scarcely toxic in nature, thereby increasing the applicability of PDS/Fe(II)/UV for the treatment of textile wastewater. This will open a perspective for the reuse of treated water in crop irrigation. Based on the results of the advanced oxidation technologies experiments, it was found that PDS/Fe(II)/UV is the best treatment method for real textile wastewater.