Discoloration of wastewater in a continuous electro-Fenton process using modified graphite electrode with multi-walled carbon nanotubes/surfactant

Enhanced in situ H2O2 electrosynthesis and leachate concentrate degradation through side-aeration and modified cathode in an electro-Fenton system

The active graphite felt (GF) catalytic layer was effectively synthesized through a wet ultrasonic impregnation-calcination method, modified with CB and PTFE, and implemented in a pioneering side-aeration electrochemical in-situ H2O2 reactor. The optimal mass ratio (CB: PTFE 1:4) for the modified cathode catalytic layer was determined using a single-factor method. Operating under optimum conditions of initial pH 5, 0.5 L/min air flow, and a current density of 9 mA/cm2, the system achieved a remarkable maximum H2O2 accumulation of 560 mg/L, with the H2O2 production capacity consistently exceeding 95 % over 6 usage cycles. The refined mesoporous structure and improved three-phase interface notably amplified oxygen transfer, utilization, and H2O2 yield. Side aeration led to an oxygen concentration near the cathode reaching 20 mg/L, representing a five-fold increase compared to the 3.95 mg/L achieved with conventional bottom aeration. In the final application, the reaction system exhibited efficacy in the degradation of landfill leachate concentrate. After a 60-minute reaction, complete removal of chroma was attained, and the TOC degradation rate surpassed 60 %, marking a sixfold improvement over the conventional system. These results underscore the substantial potential of the system in H2O2 synthesis and environmental remediation.

Approaches for filtrate utilization from synthetic gypsum production

Waste recycling and industrial wastewater treatment have always been of interest. A green approach was developed for the filtrate of synthetic gypsum production from water treatment coagulation sediments and spent sulfuric acid. Due to the high concentration of iron sulfate, concentrated filtrate showed good coagulation results, which were 5% lower than pure iron sulfate. In addition, a high concentration of iron facilitates its use as a precursor for synthesizing magnetic sorbents and photocatalysts. Such materials were synthesized by the solution combustion synthesis method. Oil sorption capacity reached 1.8 g/g, comparable to some synthetic materials and higher than sorption materials based on natural materials. Photodegradation of acid telon blue dye after 90 min of irradiation time was 82.7% with catalyst derived from filtrate compared to the just dye solution with 17.6% efficiency. The reaction rate constant for the photocatalyst sample was up to 11.4-fold higher compared with only UV treatment. The neutralized filtrate containing sulfur, calcium, magnesium, and sodium has been tested as a complex fertilizer. The results of bioindication for oil radish showed up to a 15% increase in the shoot length. A number of techno-economic indicators show that such an approach is advantageous from a technological, environmental, and economic point of view.

A new photoelectrochemical cell coupled with the Fenton reaction to remove pollutant and generate electricity under the drive of waste heat

The water and energy crises are becoming increasingly serious with rapid population and economic development. It is urgent to develop new wastewater treatment technologies with high efficiency and low energy consumption. Herein, a solar-salinity nexus cell (called PRC) integrated by a photocatalytic fuel cell and reverse electrodialysis was combined with the Fenton reaction. The PRC-Fenton process can extract electrons from organic wastewater driven by salinity gradient energy for power generation and wastewater remediation in two chambers. The Fenton cathode MOF(2Fe/Co)-GO/GF with good electrocatalytic and photocatalytic activity was developed and optimized in a three-electrode system. GO doping obviously enhanced the catalytic activity and stability of the Fenton cathode. The pollutant (ampicillin, AMP) was simultaneously removed in both anode and cathode chambers of the PRC-Fenton system. AMP removal by the MOF(2Fe/Co)-GO/GF cathode remained above 95% in a wide range of pH values (3.0-7.0). The output current of the PRC-Fenton process was 1.7-2.4 mA. Compared to similar systems, PRC-Fenton is suitable for treating toxic and refractory organic pollutants with green energy in two chambers and generating electricity.

Decolorization and Degradation of Methyl Orange Azo Dye in Aqueous Solution by the Electro Fenton Process: Application of Optimization

In a batch reactor, the EF advanced oxidation decolorization of aqueous solutions of methyl orange MO, a commercial azo reactive textile dye, was investigated in the presence of two different electrodes. The evaluation included various operational variables such as the IC current intensity (60 mA, 80 mA, and 100 mA), initial concentration of pollutant MO (20 mg/L, 40 mg/L, and 60 mg/L), initial pH of solution (3, 5, and 7), temperature of solution (20 °C, 30 °C, and 50 °C), and initial concentration of catalyst [Fe2+] (0.1 mM, 0.2 mM, and 0.3 mM) on the discoloration rate. A Box-Behnken Design of Experiment (BBD) was used to optimize the parameters that directly affect the Electro-Fenton (EF) process. Under the optimal experimental conditions such as [Fe2+] = 0.232 mM, pH = 3, IC = 80 mA, [MO] = 60 mg/L, and T = 30 ± 0.1 °C, the maximum discoloration rate achieved was 94.9%. The discoloration of the aqueous MO solution during the treatment time was confirmed by analysis of the UV-visible spectrum. After a review of the literature on organic pollutant degradation, the EF system provided here is shown to be one of the best in terms of discoloration rate when compared to other AOPs.

Recent progress in treatment of dyes wastewater using microbial-electro-Fenton technology

Globally, textile dyeing and manufacturing are one of the largest industrial units releasing huge amount of wastewater (WW) with refractory compounds such as dyes and pigments. Currently, wastewater treatment has been viewed as an industrial opportunity for rejuvenating fresh water resources and it is highly required in water stressed countries. This comprehensive review highlights an overall concept and in-depth knowledge on integrated, cost-effective cross-disciplinary solutions for domestic and industrial (textile dyes) WW and for harnessing renewable energy. This basic concept entails parallel or sequential modes of treating two chemically different WW i.e., domestic and industrial in the same system. In this case, contemporary advancement in MFC/MEC (METs) based systems towards Microbial-Electro-Fenton Technology (MEFT) revealed a substantial emerging scope and opportunity. Principally the said technology is based upon previously established anaerobic digestion and electro-chemical (photo/UV/Fenton) processes in the disciplines of microbial biotechnology and electro-chemistry. It holds an added advantage to all previously establish technologies in terms of treatment and energy efficiency, minimal toxicity and sludge waste, and environmental sustainable. This review typically described different dyes and their ultimate fate in environment and recently developed hierarchy of MEFS. It revealed detail mechanisms and degradation rate of dyes typically in cathodic Fenton system under batch and continuous modes of different MEF reactors. Moreover, it described cost-effectiveness of the said technology in terms of energy budget (production and consumption), and the limitations related to reactor fabrication cost and design for future upgradation to large scale application.

Removal of salicylic acid by electrochemical processes using stainless steel and platinum anodes

Salicylic acid is an important pharmaceutic and widely used in plant hormones and personal care products. Peroxicoagulation (PC) method has recently been employed in treatment of various pollutants. In general, carbon-based cathode materials such as graphite and carbon fiber are used for in situ H₂O₂ production and stainless steel (SS316-L) anode for low iron production in PC studies as an efficient system modification. This study was conducted to investigate salicylic acid removal efficiency of electrochemical processes. Stainless steel was used as anode in this study. It was believed that the oxidation effect of stainless steel could be responsible for partial removal of salicylic acid. In this study, stainless steel anode and graphite or carbon fiber cathodes were employed in PC treatments for removing salicylic acid from aqueous solution, and some model trials were also made to investigate the in-situ Fe²⁺ and H₂O₂ production performance. Present findings revealed a total organic carbon (TOC) removal of 30.5% and salicylic acid removal of 69.5% at optimized conditions. The EF system modification used in the study can be proposed as an easy, low-cost and effective treatment alternative for treatment of pharmaceutical industry wastes such as salicylic acid.

Removal of Methylene Blue from Aqueous Solutions by Using Nance (Byrsonima crassifolia) Seeds and Peels as Natural Biosorbents

Contamination of effluents with chemicals is a serious problem that impacts human health. Methylene blue is a cationic dye found frequently in industrial and urban sewages. In this work, dried grinded seeds and peels of nance were used as biosorbents in aqueous solutions at pH 7 and 10 (simulating urban and textile effluents) finding that Langmuir and Freundlich isotherms adequately described the sorption. Adsorption efficiencies were larger than 98% in all cases and slightly lower at pH 7 due to the closeness with the point of zero charge (pzc) of seeds and peels of nance (5.96 and 3.42, respectively). In all cases, Langmuir adsorption was favorable (RLa < 1), and Gibbs free energy of adsorption was negative indicating spontaneity, and since these values were larger than −80 but lower than 0 kJ/mol, the MB removal process was mainly due to physical interactions, a characteristic of physical adsorption. No significant differences were found amongst bulk mass transfer coefficients for the adsorption of both sorbents, indicating that both bioadsorbents had the same hydrodynamic and driving forces as well as depicted similar MB-adsorbent affinities. Interaction of MB with adsorbents was corroborated by FTIR spectroscopy, and the sorption was evidenced by scanning electron microscopy and image analysis which indicated that both adsorbents had fractal structures.

Carbonaceous cathode materials for electro-Fenton technology: Mechanism, kinetics, recent advances, opportunities and challenges

Electro-Fenton (EF) technique has gained significant attention in recent years owing to its high efficiency and environmental compatibility for the degradation of organic pollutants and contaminants of emerging concern (CECs). The efficiency of an EF reaction relies primarily on the formation of hydrogen peroxide (H₂O₂) via 2e^─ oxygen reduction reaction (ORR) and the generation of hydroxyl radicals (^●OH). This could be achieved through an efficient cathode material which operates over a wide pH range (pH 3-9). Herein, the current progresses on the advancements of carbonaceous cathode materials for EF reactions are comprehensively reviewed. The insights of various materials such as, activated carbon fibres (ACFs), carbon/graphite felt (CF/GF), carbon nanotubes (CNTs), graphene, carbon aerogels (CAs), ordered mesoporous carbon (OMCs), etc. are discussed inclusively. Transition metals and hetero atoms were used as dopants to enhance the efficiency of homogeneous and heterogeneous EF reactions. Iron-functionalized cathodes widened the working pH window (pH 1-9) and limited the energy consumption. The mechanism, reactor configuration, and kinetic models, are explained. Techno economic analysis of the EF reaction revealed that the anode and the raw materials contributed significantly to the overall cost. It is concluded that most reactions follow pseudo-first order kinetics and rotating cathodes provide the best H₂O₂ production efficiency in lab scale. The challenges, future prospects and commercialization of EF reaction for wastewater treatment are also discussed.

Gas diffusion electrodes for H2O2 production and their applications for electrochemical degradation of organic pollutants in water: A review

Nowadays, it is a great challenge to minimize the negative impact of hazardous organic compounds in the environment. Highly efficient hydrogen peroxide (H₂O₂) production through electrochemical methods with gas diffusion electrodes (GDEs) is greatly demand for degradation of organic pollutants that present in drinking water and industrial wastewater. The GDEs as cathodic electrocatalyst manifest more cost-effective, lower energy consumption and higher oxygen utilization efficiency for H₂O₂ production as compared to other carbonaceous cathodes due to its worthy chemical and physical characteristics. In recent years, the crucial research and practical application of GDE for degradation of organic pollutants have been well developed. In this review, we focus on the novel design, fundamental aspects, influence factors, and electrochemical properties of GDEs. Furthermore, we investigate the generation of H₂O₂ through electrocatalytic processes and degradation mechanisms of refractory organic pollutants on GDEs. We describe the advanced methodologies towards electrochemical kinetics, which include the enhancement of GDEs electrochemical catalytic activity and mass transfer process. More importantly, we also highlight the other technologies assisted electrochemical process with GDEs to enlarge the practical application for water treatment. In addition, the developmental prospective and the existing research challenges of GDE-based electrocatalytic materials for real applications in H₂O₂ production and wastewater treatment are forecasted. According to our best knowledge, only few review articles have discussed GDEs in detail for H₂O₂ production and their applications for degradation of organic pollutants in water.

Medical laboratory wastewater treatment by electro-fenton process: Modeling and optimization using central composite design

Medical laboratory wastewaters arising from diagnosis and examination units show highly toxic characteristic. Within the scope of the study, removal of the wastewater's toxicity and increasing BOD₅ /COD ratio of the medical laboratory wastewaters through electro-Fenton (EF) process were investigated. In the study, central composite design was applied to optimize the process parameters of EF for COD, BOD₅ , and toxicity unit (TU) removal. Based on ANOVA, H₂ O₂ /COD was found to be significant parameter for COD removal, whereas current, reaction time, and H₂ O₂ /COD were determined to be significant parameters for BOD₅ and TU removal. Optimum conditions (pH value of 3.4, current 3 A, reaction time 33.9 min, and H₂ O₂ /COD of 1.29) were determined, and predicted removals of COD, BOD_5, and TU were found to be 55.1%, 42.5%, and 99.7% and experimental removals were found to be 53.4%, 41.2%, and 99.5%, respectively. TU value of the wastewater decreased from the value of 163-0.815, and BOD₅ /COD value increased from the value of 0.32-0.39. The results of the study indicate that EF process is an effective treatment option for COD, BOD_5, and especially toxicity removal from medical laboratory wastewater. PRACTITIONER POINTS: Electro-Fenton process was applied medical laboratory wastewater with highly toxic characteristic. Response surface methodology approach using central composite design was employed for modeling. 53.4%, 41.2%, and 99.5% of COD, BOD_5, and toxicity removals were achieved under statistically optimized conditions. TU value of the wastewater decreased from the value of 163-0.815. BOD₅ /COD value increased from the value of 0.32-0.39.

Degradation of glyphosate herbicide by an electro-Fenton process using carbon felt cathode

An electro-Fenton system, which consists of a Pt gauze anode and a commercial carbon felt cathode, is commonly employed to generate in situ hydrogen peroxide, hydroxyl radical and regenerate ferrous catalyst for glyphosate degradation (a widely used herbicide in Vietnam) in aqueous solution. The absorbance measurements used to determine the glyphosate concentration during the electrolysis proved that glyphosate was degraded by pseudo-first-order kinetic. The influence of pH, current density, catalyst concentration and initial content of the glyphosate on mineralisation efficiency were studied by monitoring the total organic carbon (TOC) and hydrogen peroxide concentration during electrolysis. The results show that the maximal removal percentage of glyphosate was 91.91% with applied current density of 10 mA cm-2, pH 3, 0.1 mM Fe2+, 0.05 M Na2SO4, and 0.1 mM glyphosate in 40 min. The degrading rate constant of glyphosate degradation was calculated to be kapp = 0.063 min-1. In this 91.91% removal, 81.65% of glyphosate was mineralised and the remainder consists of intermediates produced during the electro-Fenton process.

Fabrication of multi-walled carbon nanotubes and carbon black co-modified graphite felt cathode for amoxicillin removal by electrochemical advanced oxidation processes under mild pH condition

Hydrogen peroxide (H₂O₂) electrogenerated via two-electron oxygen reduction reaction at cathode plays an important role in electrochemical advanced oxidation processes for organic pollutants removal from wastewater. Herein, multi-walled carbon nanotubes and carbon black co-modified graphite felt electrode (MWCNTs-CB/GF) was prepared as an efficient cathode for H₂O₂ electrogeneration and amoxicillin removal by anodic oxidation with hydrogen peroxide (AO-H₂O₂) and electro-Fenton (EF) under mild pH condition. Besides, the physicochemical and electrochemical properties of MWCNTs-CB/GF were characterized by scanning electron microscopy, N₂ adsorption and desorption experiment, contact angle measurement, X-ray photoelectron spectroscopy, and linear sweep voltammetry. Compared with GF, MWCNTs-CB/GF showed a higher H₂O₂ generation of 309.0 mg L^-1 with a current efficiency of 60.9% (after 120 min) and more effective amoxicillin removal efficiencies of 97.5% (after 120 min) and 98.7% (after 30 min) in AO-H₂O₂ and EF (with 0.5 mM Fe²⁺) processes, under the condition of current density 12 mA cm^-2 and initial pH 5.5. Meanwhile, the TOC removal efficiency was 45.2% during EF process after 120 min. Anodic oxidation, H₂O₂ oxidation, and methanol capture indicated that ∙OH generated via electro-activation reaction at MWCNTs-CB/GF and Fenton reaction in solution played the dominant role in amoxicillin removal. Moreover, the TOC removal was associated with ∙OH generated during Fenton reaction in the solution. The major intermediates of AMX degradation by EF process were identified using LC-MS and the possible degradation pathways were proposed containing of β-lactam ring opening, hydroxylation reaction, decarboxylation reaction, methyl groups in the thiazolidine ring oxidation reaction, bond cleavage, and rearrangement processes. All of the above results proved that MWCNTs-CB/GF was an excellent cathode for AMX degradation under mild pH condition.

GO/PEDOT:NaPSS modified cathode as heterogeneous electro-Fenton pretreatment and subsequently aerobic granular sludge biological degradation for dye wastewater treatment

Heterogeneous electro-Fenton (EF) technology has been wildly applied for the treatment of wastewater containing dyes and other organic pollutants. However, biologically treatment should be further applied after heterogeneous electro-Fenton process in order get better effluent quality. In the present study, a simple electropolymerization method using poly (3,4-ethylenedioxythiophene) (PEDOT) and graphene oxide (GO) was applied for graphite felt (GF) electrode modification as cathode in EF system, and coupling subsequently aerobic granular sludge (AGS) biological treatment for dye wastewater treatment. The modified electrode was characterized by scanning electron microscopy (SEM), Raman spectrum, and cyclic voltammetry (CV). Data implied that much higher H₂O₂ productivity, current response and coulomb efficiency (CE) were achieved by using GO/PEDOT:NaPSS modified GF. The results could be ascribed to the synergistic effect between PEDOT and GO that accelerated the electron transfer rate. Moreover, the H₂O₂ production capacity remained over 84.2% after 10-times reuses for GO/PEDOT:NaPSS modified GF, indicating that GO significantly improved the stability and life of electrode. Compared with the single system, the total organic carbon (TOC) and chemical oxygen demand (COD) removal efficiencies of the combined system degradation methylene blue (MB) wastewater were significantly improved. Therefore, this modified GF could be used as a potentially useful cathode in heterogeneous EF technology for actual wastewater treatment and the combined system have a promising engineering application value in MB wastewater degradation field.

Fe-Nanoporous Carbon Derived from MIL-53(Fe): A Heterogeneous Catalyst for Mineralization of Organic Pollutants

Catalytic electrodes were prepared via carbonization of MIL-53(Fe) on the surface of porous carbon felt electrodes (CF) for use in wastewater treatment by the heterogeneous electro-Fenton (EF) process. The best results were obtained when the carbon felt was pretreated with nitric acid, enhancing the affinity of the MIL-53(Fe) for the surface. Following a series of optimization experiments, carbonization conditions of 800 °C for 5 h were used to form Fe-nanoporous carbon (MOFs@CF). The as-prepared electrodes were used as both cathode and heterogeneous catalyst in the EF process for the mineralization of exemplar dye Acid Orange 7 (AO7). Total organic carbon (TOC) removal of 46.1% was obtained within 8 h of electrolysis at around neutral pH (6.5) and the electrode retained over 80% of its original efficiency over five treatment cycles.

Transformation products and degradation pathway of textile industry wastewater pollutants in Electro-Fenton process

In this study, pollutants from textile industry wastewater were transformed/oxidized using Ti/RuO₂ electrode by Electro-Fenton (EF) method in a continuous reactor. The performance was evaluated in terms of % COD removal, % color removal and energy consumed. Electrolysis time, retention time, current, and ferrous sulphate concentration as Fenton catalyst were selected as EF process parameters. To determine the optimum operating conditions multiple response optimization with desirability approach based on central composite design under response surface methodology was used. Spectrophotometric and GC-MS analysis were performed to identify the degraded/transformation compounds, and on this basis degradation mechanism during EF process as well as disposability of treated wastewater was analyzed. Further, bioassay test of treated textile wastewater was conducted for toxicity analysis in view of its disposal quality. Results showed that all the components of textile wastewater were totally eliminated/transformed in lower molecular weight compounds after EF treatment of textile effluent. Further, bioassay test analysis confirmed the nontoxic nature of treated wastewater.

Rolling-made gas diffusion electrode with carbon nanotube for electro-Fenton degradation of acetylsalicylic acid

H₂O₂ production plays an important role in electro-Fenton process for pharmaceutical and personal care products (PPCPs) degradation. In this work, carbon nanotube (CNT) was attempted to make a gas diffusion electrode (GDE) by rolling method to achieve a high H₂O₂ production and current efficiency, and it was further used as electro-Fenton cathode for the degradation of acetylsalicylic acid (ASA) as one kind of PPCPs. The optimal amount of catalyst layer was 0.15 g CNT and 93.75 μL PTFE, obtaining the production of H₂O₂ of 805 mg L^-1 in 0.05 mM Na₂SO₄ solution at 100 mA after 180 min. The degradation of ASA by electro-Fenton on such a CNT-GDE cathode was studied, and some important parameters such as current, pH as well as the dosage of Fe²⁺ were optimized. The degradation ratio of ASA could achieve almost 100% after 10 min and the TOC removal ratio was 62% at 1 h under the condition of 100 mA and pH 3, showing a great potential for the treatment of PPCPs.

In-situ synthesis of 3D GA on titanium wire as a binder- free electrode for electro-Fenton removing of EDTA-Ni

Ethylenediaminetetraacetic acid (EDTA) could form stable complexes with toxic metals such as nickel due to its strong chelation. The three-dimensional (3D) macroporous graphene aerogels (GA), which was in-situ assembled by reduced graphene oxide (rGO) sheets on titanium wire as binder-free electrode, was presented as cathode for the degradation of EDTA-Ni in Electro-Fenton process. The X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM) and Brunauer-Emmett-Teller (BET) results indicated 3D GA formed three dimensional architecture with large and homogenous macropore structure and surface area. Cyclic Voltammetry (CV), Linear Sweep Voltammetry (LSV) and Rotating Ring-disk Electrode (RRDE) results showed that the 3D GA cathode at pH 3 displayed the highest current density and electrochemical active surface area (ECSA), and better two-electron selectivity for ORR than other pH value, confirming the 3D-GA cathode at pH 3 has the highest electrocatalytic activity and generates more H₂O₂. The factors such as pH, applied current density, concentration of Fe²⁺, Na₂SO_4, and aeration rates of air were also investigated. Under the optimum conditions, 73.5% of EDTA-Ni was degraded after reaction for 2h. Mechanism analysis indicated that the production of OH on the 3D GA cathode played an important role in the removal of EDTA-Ni in the 3D GA-EF process, where the direct regeneration of Fe²⁺ on the cathode would greatly reduce the consumption of H₂O₂. Therefore, it is of great promise for 3D-GA catalyst to be developed as highly efficient, cost-effective and durable cathode for the removal of EDTA-Ni.

Ultrahigh yield of hydrogen peroxide and effective diclofenac degradation on a graphite felt cathode loaded with CNTs and carbon black: an electro-generation mechanism and a degradation pathway

A new graphite felt cathode loaded with carbon nanotubes and carbon black was developed.

Alkaline electrochemical advanced oxidation process for chromium oxidation at graphitized multi-walled carbon nanotubes

Alkaline electrochemical advanced oxidation processes for chromium oxidation and Cr-contaminated waste disposal were reported in this study. The highly graphitized multi-walled carbon nanotubes g-MWCNTs modified electrode was prepared for the in-situ electrochemical generation of HO₂^-. RRDE test results illustrated that g-MWCNTs exhibited much higher two-electron oxygen reduction activity than other nanocarbon materials with peak current density of 1.24 mA cm^-2, %HO₂^- of 77.0% and onset potential of -0.15 V (vs. Hg/HgO). It was originated from the highly graphitized structure and good electrical conductivity as illustrated from the Raman, XRD and EIS characterizations, respectively. Large amount of reactive oxygen species (HO₂^- and ·OH) were in-situ electro-generated from the two-electron oxygen reduction and chromium-induced alkaline electro-Fenton-like reaction. The oxidation of Cr(III) was efficiently achieved within 90 min and the conversion ratio maintained more than 95% of the original value after stability test, offering an efficient and green approach for the utilization of Cr-containing wastes.

Mineralization of the textile dye acid yellow 42 by solar photoelectro-Fenton in a lab-pilot plant

A complete mineralization of a textile dye widely used in the Chilean textile industry, acid yellow 42 (AY42), was studied. Degradation was carried out in an aqueous solution containing 100mgL(-1) of total organic carbon (TOC) of dye using the advanced solar photoelectro-Fenton (SPEF) process in a lab-scale pilot plant consisting of a filter press cell, which contains a boron doped diamond electrode and an air diffusion cathode (BDD/air-diffusion cell), coupled with a solar photoreactor for treat 8L of wastewater during 270min of electrolysis. The main results obtained during the degradation of the textile dye were that a complete transformation to CO2 depends directly on the applied current density, the concentration of Fe(2+) used as catalyst, and the solar radiation intensity. The elimination of AY42 and its organic intermediates was due to hydroxyl radicals formed at the anode surface from water oxidation and in the bulk from Fenton's reaction between electrogenerated H2O2 and added Fe(2+). The application of solar radiation in the process (SPEF) yield higher current efficiencies and lower energy consumptions than electro-Fenton (EF) and electro-oxidation with electrogenerated H2O2 (E OH2O2) by the additional production of hydroxyl radicals from the photolysis of Fe(III) hydrated species and the photodecomposition of Fe(III) complexes with organic intermediates. Moreover, some products and intermediates formed during mineralization of dye, such as inorganic ions, carboxylic acids and aromatic compounds were determined by photometric and chromatographic methods. An oxidation pathway is proposed for the complete conversion to CO2.

Photocatalytic discoloration of Acid Red 14 aqueous solution using titania nanoparticles immobilized on graphene oxide fabricated plate

Textile industry consumes remarkable amounts of water during various operations. A significant portion of the water discharge to environment is in the form of colored contaminant. The present research reports the photocatalytic degradation of anionic dye effluent using immobilized TiO2 nanoparticle on graphene oxide (GO) fabricated carbon electrodes. Acid Red 14 (AR 14) was used as model compound. Graphene oxide nanosheets were synthesized from graphite powder using modified Hummer's method. The nanosheets were characterized with field emission scanning electron microscope (FESEM) images, X-ray diffraction (XRD) and FTIR spectrum. The GO nanoparticles were deposited on carbon electrode (GO-CE) by electrochemical deposition (ECD) method and used as catalyst bed. TiO2 nanoparticles were fixed on the bed (GO-CE- TiO2) with thermal process. Photocatalytic processes were carried out using a 500 ml solution containing dye in batch mode. Each photocatalytic treatment were carried out for 120 min. Effect of dye concentration (mg/L), pH of solution, time (min) and TiO2 content (g/L) on the photocatalytic decolorization was investigated.

Effective degradation of rhodamine B by electro-Fenton process, using ferromagnetic nanoparticles loaded on modified graphite felt electrode as reusable catalyst: in neutral pH condition and without external aeration

Polytetrafluoroethylene/ferromagnetic nanoparticle/carbon black (PTFE/MNP/CB)-modified graphite felt (GF) was successfully applied as cathode for the mineralization of rhodamine B (RhB) in electro-Fenton (EF) process. The modified cathode showed high decolorization efficiency for RhB solution even in neutral pH condition and without external aeration, achieving nearly complete decolorization and 89.52 % total organic carbon (TOC) removal after 270-min oxidation with the MNP load 1.2 g at 50 A/m(2). Moreover, the operational parameters (current density, MNP load, initial pH, and airflow rate) were optimized. After that, adsorption isotherm was also conducted to compare the absorption quantity of CB and carbon nanotube (CNT). Then, the surface morphologies of MNPs were characterized by transmission electron microscope (TEM), energy-dispersive X-ray detector (EDX), and Fourier transform infrared spectroscopy (FTIR); and the modified cathode was characterized by SEM and contact angle. Finally, the stability and reusability of modified cathode were tested. Result uncovered that the PTFE/MNP/CB-modified cathode has the potential for industrial application and the solution after treatment was easily biodegradable.