Designing the Mineralization of a Wastewater Sample from a Coating Industry

Design of Fenton and photo‐Fenton reactions was partially automated by using sequential injection analysis (SIA) and response surface methodology for the treatment of a wastewater sample from a coatings industry. The extension of both Fenton and photo‐Fenton reactions was evaluated by the percentage of total organic carbon (TOC) remaining in solution after 15 min of reaction. Use of small volumes of sample and reagents, as well as easy solution handling, were the remarkable features of the proposed system. The highest percentage of TOC removal (79%) was obtained by the photo‐Fenton reaction at the following initial mass‐based concentration ratios: H₂O₂/TOC = 10, H₂O₂/FeSO₄ = 50, and pH 2.5. The best result for Fenton reaction indicated a TOC removal of only 45%, obtained at H₂O₂/initial TOC = 20, H₂O₂/FeSO₄ = 30, and pH 2.5. The SIA system was designed to dispense reagents to the sample flasks and to drive the sample intended to photo‐Fenton reaction through a homemade photo‐reactor. Modifications in chemical parameters of the reactions were achieved via the software commanding the SI system, without the need for physical reconfiguration of reagents around the selection valve.     

Color Removal from Synthetic Textile Wastewater by Sono‐Fenton Process

In this study, the oxidative decolorization of C.I. reactive yellow 145 (RY 145) from synthetic textile wastewater including RY 145 and polyvinyl alcohol by Fenton and sono‐Fenton processes which are the combination of Fenton process with ultrasound has been carried out. The effects of some operating parameters which are the initial pH of the solution, the initial concentration of Fe²⁺, H₂O₂, and the dye, temperature, and agitation speed on the color and chemical oxygen demand (COD) removals have been investigated. The optimum conditions have been found as [Fe²⁺] = 20 mg/L, [H₂O₂] = 20 mg/L, pH 3 for Fenton process and [Fe²⁺] = 20 mg/L, [H₂O₂] = 15 mg/L, pH 3 for sono‐Fenton process by indirectly sonication at 35 kHz ultrasonic frequency and 80 W ultrasonic power. The color and COD removal efficiencies have been obtained as 91 and 47% by Fenton process, and 95 and 51% by sono‐Fenton processes, respectively. Kinetic studies have been performed for the decolorization of RY 145 under optimum conditions at room temperature. It has been determined that the decolorization has occurred rapidly by sono‐Fenton process, compared to Fenton process.     

Optimization of a Photo‐assisted Fenton Oxidation Process: A Statistical Model for MDF Effluent Treatment

In the present study, the effects of initial COD (chemical oxygen demand), initial pH, Fe²⁺/H₂O₂ molar ratio and UV contact time on COD removal from medium density fiberboard (MDF) wastewater using photo‐assisted Fenton oxidation treatment were investigated. In order to optimize the removal efficiency, batch operations were carried out. The influence of the aforementioned parameters on COD removal efficiency was studied using response surface methodology (RSM). The optimal conditions for maximum COD removal efficiency from MDF wastewater under experimental conditions were obtained at initial COD of 4000 mg/L, Fe²⁺/H₂O₂ molar ratio of 0.11, initial solution pH of 6.5 and UV contact time of 70 min. The obtained results for maximum COD removal efficiency of 96% revealed that photo‐assisted Fenton oxidation is very effective for treating MDF wastewater.     

Degradation of Phenol in Aqueous Solution by Fenton,Sono‐Fenton and Sono‐photo‐Fenton Methods

The present work focuses on the performance of Fenton, sono‐Fenton, and sono‐photo‐Fenton processes for the oxidation of phenol present in aqueous solution. The effects of H₂O₂ concentration, Fe²⁺ concentration, pH, and initial phenol concentration on the oxidation of phenol were studied. The optimum Fe²⁺ and H₂O₂ concentrations for the Fenton process were 45 and 800 mg/L, respectively. For the sono‐Fenton process, the optimum Fe²⁺ and H₂O₂ concentrations were 30 and 800 mg/L, respectively. The optimal conditions for the sono‐photo‐Fenton process were found to be 20 mg/L of Fe²⁺ and 700 mg/L of H₂O₂. The optimum pH was found to be 3 for the processes investigated in the present study. The analysis of results showed that the sono‐photo‐Fenton method reduced the Fe²⁺ concentration by 30–50% and the H₂O₂ concentration by 12.5%. It was found that the sono‐photo‐Fenton technique showed better performance than the Fenton and sono‐Fenton processes for the oxidation of phenol. A lumped kinetic model was used to predict the chemical oxygen demand reduction and the model was found to fit the data.     

Treatability of Dye Solutions Containing Disperse Dyes by Fenton and Fenton‐Solar Light Oxidation Processes

This study attempts to explore the possibility of treating dye solutions containing Disperse Yellow 119 and Disperse Red 167 by Fenton and Fenton under solar‐light oxidation processes. Experiments were conducted to examine the effects of various operating conditions on the performance of the treatment systems. The Fenton results showed that 98.6% spectral absorption coefficient (SAC) and 90.8% chemical oxygen demand (COD) removals were proved at pH 3, 50 mg/L Fe²⁺, and 75 mg/L H₂O₂, 15 min oxidation time for Disperse Yellow 119. After 40 min solar irradiation time during Fenton process the SAC removal was 99.1%. COD reduction of about 98.3% was observed at the same time. It was also obtained as 97.8% SAC and 97.7% COD removal with pH 3, 75 mg/L Fe²⁺, 100 mg/L H₂O₂, and 25 min oxidation time for Disperse Red 167 at this optimum conditions. For Disperse Red 167 during Fenton under solar light process, after 40 min of solar irradiation time the SAC and COD reduction were obtained 99.3 and 98.4%, respectively.     

Degradation of Monoazo Pigments Red 53:1 and Red 48:2 by Fenton,Photo‐Fenton and UV/Peroxide Reactions

The degradation reactions of two monoazo pigments, namely, Red 53:1 and Red 48:2, by Fenton, photo‐Fenton and UV/H₂O₂ systems have been studied. The efficiencies of the Fenton reactions increased with temperature, but the formation of solid agglomerates was observed when the reactions were carried out above 50°C indicating a coagulant action of Fe⁺² or Fe⁺³. Photo‐Fenton reactions irradiated by sunlight presented the best rate constants for cleavage of the azo bond and the naphthalene rings. The UV/H₂O₂ system exhibited the highest efficiency with respect to the consumption of H₂O₂. The presence of a carbonyl group in the ortho position of the naphthol ring hampered the oxidation of pigment Red 48:2 by hydroxyl radicals. This finding may be explained in terms of the acceptor character of the COOH group, and suggests the formation of a complex containing two six‐membered rings between Fe⁺³ and the pigment molecule.     

Mineralization of Catechol by Fenton and Photo‐Fenton Processes

Catechol is one of the most abundant phenolic components of olive mill wastewaters. In this article, the mineralization of this compound in synthetic aqueous solutions by the Fenton and photo‐Fenton processes is studied. It has been found that for 1.44 mM catechol, the total organic carbon of solutions is reduced about 94.4% at best after 60 min of Fenton treatment at optimized conditions of pH 3.0, 0.2 mM Fe²⁺, 7.09 mM H₂O₂, and 25°C. A faster and overall mineralization is attained by applying photo‐Fenton with UVA irradiation. o‐Benzoquinone, 1,2,3‐trihydroxybenzene and 1,2,4‐trihydroxybenzene were identified by GC–MS as primary quinonic and polyhydroxylated derivatives. Small amounts of generated carboxylic acids like muconic, maleic, malonic, acetic, oxalic, and formic acids were detected by ion‐exclusion chromatography. The Fe(III) complexes of these acids persist in the medium under Fenton conditions, while their photolysis by UVA light and that of other by‐products account for by the faster degradation and total mineralization achieved in the photo‐Fenton process. A reaction sequence for catechol mineralization by Fenton and photo‐Fenton involving all intermediates detected is proposed.     

Solar Photocatalytic Decolorization and Detoxification of Industrial Batik Dye Wastewater Using P(3HB)‐TiO2 Nanocomposite Films

Solar photocatalytic decolorization and detoxification of batik dye wastewater using titanium dioxide (TiO₂) immobilized on poly‐3‐hydroxybutyrate (P(3HB)) film was studied. The effects of initial dye concentration, catalyst concentration, P(3HB) film thickness, and fabrication methods of the nanocomposite films were evaluated against methylene blue, a standard organic dye. It was observed that 0.4 g of P(3HB)‐40 wt% TiO₂ removed 96% of the color under solar irradiation. P(3HB) and TiO₂, mixed concurrently in chloroform followed by stirring for 24 h showed a more even distribution of the photocatalyst on the polymer surface and yielded almost 100% color removal. The photocatalytic films were able to completely decolorize real industrial batik dye wastewater in 3 h and induced a chemical oxygen demand (COD) reduction of 80%. Reusability of the 0.4 g P(3HB)‐40 wt% TiO₂ film in decolorizing the batik dye wastewater was also possible as it gave a high consistent value of decolorization percentage (>80%) even after the sixth repeated usage. Recovery step of the photocatalysts was also not required in this simple treatment system. The decolorized batik dye wastewater had less/no toxic effects on mosquito larvae, Aedes aegypti, and microalgae, Scenedesmus quadricauda indicating simultaneous detoxification process along with the decolorization process.     

Pickling Waste as an Inexpensive Iron Source for Fenton Oxidation of Synthetic Dye Bath Waste

A simple, low cost, highly effective, and useful Fenton oxidation treatment of synthetic dye bath waste with pickling liquor as a source of iron (Fe²⁺ catalyst) is reported. Optimizations of contact time, Fe²⁺ and H₂O₂ doses are carried out. Oxidative de‐colorization and degradation of Reactive Blue 4 and Reactive Orange 16 was measured in terms of decrease in absorbance at their wavelength of maximum absorption (RB4, 599 nm; and RO16, 493 nm) and also as reduction in chemical oxygen demand (COD). Approximately, 62% COD was removed in 2 h at optimized doses of Fe²⁺ (8.95 mM) and H₂O₂ (61.8 mM) by using pickling waste as a source of Fe²⁺ catalyst. Similar performance efficiency was observed when neat FeSO₄ was used as a source of Fe²⁺, indicating that pickling liquor can be a low cost source of Fe²⁺ to treat synthetic dye bath waste by Fenton method.     

Spinel Ferrite Mediated Photo‐Fenton Degradation of Phenolic Analogues: A Detailed Study Employing Two Distinct Inorganic Oxidants

The present work demonstrates the applicability of ferrites as photo‐Fenton catalysts for deterioration of different phenolic derivatives. To analyze optimal reaction conditions, experiments are performed with four magnetic spinel ferrites MFe₂O₄ (M = Co, Cu, Ni, and Zn) and two inorganic oxidants, i.e., hydrogen peroxide (HP) and potassium peroxymonosulfate (PMS). The reactions are performed using p‐nitrophenol as phenolic probe. CuFe₂O₄ and CoFe₂O₄ possessed excellent ability to activate HP and PMS, respectively, among all four synthesized catalysts. A noteworthy aspect of two oxidizing agents is that the concentration of PMS used during the reaction is four times less than HP. Further, the broad pH activity of PMS provides a significant advantage over HP. The optimal reaction conditions, when HP is the oxidant in the photo‐Fenton degradation, are 0.50 g L^?1 MFe₂O₄, pH 2.5, and 8.8 mM HP. Although PMS is active in a wide pH range (2–10), adequate reaction conditions are 0.50 g L^?1 MFe₂O₄, natural pH, and 2.2 mM PMS. The photo‐Fenton activity of ferrites is extended to the degradation of different nitro‐ and chloro‐analogs of phenol (2‐nitrophenol, 3‐nitrophenol, 4‐nitrophenol, 2,4‐dinitrophenol, 2,4,6‐trinitrophenol, 2‐chlorophenol, 3‐chlorophenol, 4‐chlorophenol, 2,4‐dichlorophenol) with only two ferrites (CuFe₂O₄ and CoFe₂O₄). A comparative study is performed with the two oxidants (HP and PMS) with positive results. Finally, stability and reusability of magnetic ferrites as catalysts are also studied to prove their use in phenolic solution treatment.     

Electro‐Fenton Treatment of Photographic Processing Wastewater

In this work, the treatment of photographic processing wastewaters (PPW) by electro‐Fenton process has been investigated. The Influence of operating conditions on kinetics and efficiency of electro‐Fenton process has been evaluated using carbon felt cathode and platinium (Pt) or boron‐doped diamond (BDD) anode. The results of electro‐Fenton treatment of PPW have shown that nearly complete removal of total phenols was obtained for all combinations with pseudo‐first rate constants of 0.07, 0.012, and 0.018/min for carbon felt/Pt, carbon felt/BDD and Pt/BDD cathode/anode combinations, respectively. The combination of carbon felt cathode with BDD anode achieved the highest total organic carbon (TOC) removal of 90%, while it did not exeed 40% for carbon felt/Pt combination. Increasing current intensity and Fe²⁺ dose enhances the efficiency of electro‐Fenton process. However, increasing pH decreases TOC removal during the treatment of PPW by electro‐Fenton process. The highest efficiency of electro‐Fenton process using BDD anode can be explained by the contribution of direct and indirect oxidation routes in the degradation mechanism of organics including (i) oxidation via hydroxyl radicals generated from the catalytic decomposition of H₂O₂ and from water discharge on BDD anode, (ii) direct oxidation of certain organic compounds on BDD anode, and (iii) mediated oxidation with inorganic oxidants electrogenerated from anodic oxidation of supporting salts.     

Oxidative Degradation of Orange II Dye in Water with Raw and Acid‐Treated ZnO,and MnO2

Commercial ZnO, MnO₂, and their acid‐treated forms were used as catalysts for oxidative degradation of Orange II dye in water. ZnO and MnO₂ were treated with 0.5, 0.75, or 1.0 N aqueous H₂SO₄. The acid treated oxides were found to be highly effective in bringing about degradation of Orange II in water. As much as 68.7% of the dye in an aqueous solution of 1 mg/L concentration could be degraded with untreated ZnO as the catalyst. The degradation increased to 79.5% with 1.0 N acid treated ZnO as the catalyst when the reaction was carried out at room temperature for 240 min. The catalytic activity was slightly affected by the solution pH in the range of 2.0–8.0. With MnO₂ as the catalyst, there was only 12.7% degradation of the dye, but this increased up to 100% when 0.5 N acid treated MnO₂ was used as the catalyst. It was found that a catalyst loading of 5.0 g/L of raw and acid‐treated ZnO and a loading of 0.5 g/L of raw and acid‐treated MnO₂ could bring about almost 100% degradation of Orange II in water in an interaction time of 240 min at room temperature.     

Reductive Dechlorination of PCBs Using Photocatalyzed UV Light

Feasibility of photocatalytic dechlorination of PCB‐138 and Aroclor‐1254 using platinum loaded TiO₂ (P25) in an alkaline 2‐propanol medium has been investigated. Experiments were conducted in batch mode using a Rayonet photo‐reactor under aerated and deaerated conditions with black lamps emitting around 350 nm as light source. Two forms of platinum deposition were investigated: Photochemically loaded P25 as well as addition of potassium hexachloroplatinate into the reaction medium. Partial dechlorination of PCBs was observed after 7 h of irradiation with pure TiO₂ as catalyst when the reaction vessel was kept open to air. Complete dechlorination was observed after 5 h of irradiation in a deaerated environment. Enhanced photocatalytic efficiency was observed when platinum deposited P25 was used as catalyst, with the best result being obtained when aqueous potassium hexachloroplatinate was added into the reaction medium. Lower potassium hexachloroplatinate concentration (0.1 mM) yielded better performance.     

Kinetics of Methyldiethanolamine Mineralization by Using UV/H2O2 Process

The UV/H₂O₂ is one of the popular techniques in the advanced oxidation processes (AOPs) and has been applied in the wastewater treatment during recent two decades. UV exposure on the H₂O₂ generate highly reactive hydroxyl radicals (OH^?), which are used to degrade organic contaminants through oxidation processes in wastewater. This present study involves the estimation of hydroxyl radical rate constants of methyldiethanolamine (MDEA) mineralization at different temperatures by using UV/H₂O₂ in aqueous solution. Laboratory experiments have been conducted and the profile of MDEA mineralization has been established. The hydroxyl radical rate constants and the activation energy of mineralization process have been calculated. The estimated hydroxyl rate constants and the activation energy are in good agreement with those reported in the literature.     

Anodic Oxidation as Green Alternative for Removing Diethyl Phthalate from Wastewater Using Pb/PbO2 and Ti/SnO2 Anodes

The electrochemical oxidation (EO) of diethyl phthalate (DEP) in aqueous solution was studied at Pb/PbO₂ and Ti/SnO₂ anode materials under galvanostatic‐experimental conditions. Results obtained clearly demonstrated that the anode plays a significant role for the optimization of the oxidation process, deciding the mechanisms and by‐products formed. DEP and by‐products of oxidation were also analyzed during various stages of the electrolysis reaction by HPLC and GC/MS techniques. Before the analysis by GC/MS technique, the samples were treated by solid phase microextraction (SPME) in order to concentrate the compounds from the reaction solution and identify all electrolysis intermediates. Current efficiencies (instantaneous current efficiency; ICE and total current efficiency; TCE) achieved during EO experiments were dependent on anode used and current density (20–40 mA cm^?2) at 40°C. The results obtained demonstrated that the environmental electrochemical methods can be a feasible alternative for the wastewater treatment containing hazardous phthalates.     

Characterization and advanced oxidation treatment of dyeing effluent by Fenton’s reagent

Textile effluent from dyeing process has been a serious environmental threat for years. This study was intended to evaluate the performance of Fenton’s process for the removal of chemical oxygen demand (COD), colour and turbidity. Experiments were conducted by laboratory-scale reactors fed with cotton dyeing effluent. The Fenton process employs ferrous ions and hydrogen peroxide H₂O₂ under acidic pH conditions. The experimental variables studied include doses of iron salts and hydrogen peroxide, oxidation time, pH for oxidation and coagulation. The COD, color and turbidity removal reached a maximum of 97.2, 96.8 and 84.8% respectively at a reaction time of 20 min under optimum doses of H₂O₂ and Fe²⁺. Hydrogen peroxide dose ranging from 0.5 to 2.0 mL/500 mL and FeSO₄ · 7H₂O in the range of 0.5–4.0 gm/500 mL were selected to be examined at different reaction times between 10 and 30 min. Optimum dose of hydrogen peroxide and ferrous sulphate were 2.0 mL and 1.0 gm respectively for 500 mL of sample. In this study optimized pH 4.0 and 6.0 was found effective for oxidation and coagulation respectively.     

Supported TiO2 on Kaolin,Cordierite, and Calcite for Photocatalytic Removal of Dyes from Wastewater

Kaolin, cordierite, and calcite are investigated as supports for TiO₂. The prepared TiO₂/support samples are examined for the removal of organic dyes from wastewater. The samples are preliminarily investigated to identify the optimal loaded system using synthetic wastewater containing methylene blue (MB). Data indicate that the investigated support significantly affects the photocatalytic activity of the supported TiO₂. Low photocatalytic activity toward MB degradation is observed upon using TiO₂/calcite when compared to the unsupported TiO₂. Interaction between calcite and titania species probably occurrs to produce the less photoactive CaTiO₃ amorphous species. Anatase TiO₂ is obtained upon using kaolin and cordierite as supports. The low photocatalytic performance of the TiO₂/kaolin sample is also observed. A high concentration of MB on TiO₂/kaolin surfaces blocks the photoactive sites. TiO₂/cordierite shows the highest photocatalytic activity compared to the unsupported TiO₂ as well as the other TiO₂/support samples. Rigid cordierite particles suppress the agglomeration of TiO₂ particles during the preparation, leading to a high exposed surface of TiO₂ towards light illumination. TiO₂/cordierite is investigated for the removal of organic dye from real wastewater collected from a textile dyeing factory. Color removal of up to 46% is achieved upon UV irradiation.     

Photocatalytic Degradation of Dye C.I. Direct Blue 78 Using TiO2 Nanoparticles Immobilized on Recycled Wool‐Based Nonwoven Material

This paper discusses the possibility of immobilization of TiO₂ nanoparticles onto recycled wool‐based nonwoven material, which can be utilized for removal of dyes from wastewater. The photocatalytic activity of TiO₂ nanoparticles deposited on the nonwoven material was evaluated in the aqueous solution of direct dye C.I. Direct Blue 78 under the UV illumination. Nonwoven material modified with TiO₂ nanoparticles provides complete removal of dye from the solution already after 4–6 h of UV illumination. However, photodegradation of the dye adsorbed on the nonwoven material was obtained within 24 h of UV illumination. The rate of dye adsorption and photodegradation depends on the amount of deposited TiO₂ nanoparticles. The increase of initial dye concentration induced decrease in photocatalytic efficiency of immobilized TiO₂ nanoparticles. The highest photodegradation rate was achieved in acidic conditions. Elevated temperatures positively affected the removal of dye from solution. Photocatalytic activity of TiO₂ nanoparticles deposited on nonwoven material was preserved after three photodegradation cycles.     

Degradation of Acid Pharmaceuticals in the UV/H2O2 Process: Effects of Humic Acid and Inorganic Salts

The presence of acid pharmaceuticals in water environments poses a potential threat to ecosystems and human health. Recent research has shown that photo oxidation processes are much more effective for removing these pharmaceuticals. However, the existence of humic acid (HA) could inhibit the clearance efficiency of this process. In this study, we investigated the photochemical degradation of six selected acid pharmaceuticals in surface water and effluent from wastewater treatment plants using the UV/H₂O₂ process. The results showed that HA can act as a photo sensitizer or a ^. OH sink, and its concentration had a significant inhibitory effect on the degradation of acid pharmaceuticals. Most of these pharmaceuticals were inhibited during this process when HA was added to deionized water solutions. In addition, the effects of chloride, bicarbonate, and nitrate on the degradation of these pharmaceuticals were different. The removal efficiency of these acid pharmaceuticals is lower in natural samples than in deionized samples because of the complex constituents in the latter.     

Treatment of a Trifluraline Effluent by Means of Oxidation‐Coagulation with Fe(VI) and Combined Fenton Processes

The amination water (AW) effluent stream from the industrial production of the trifluraline herbicide was submitted to an oxidation‐coagulation treatment with potassium ferrate, combined with advanced oxidation processes. The experimental results obtained by analysis of variance (ANOVA) for the oxidation‐coagulation‐Fenton process, evaluating the variables pH (A), Fe(VI) concentration (B), and H₂O₂ concentration (C), demonstrated that the regression equation resulting from the Response Surface Methodology (RSM) experimental design, for the quadratic model, was η_Abs (%) = 36.9– 21.58A + 8.37A² + 1.36B + 0.92B² + 1.08C + 1.52C² + 1.27AB – 1.34AC + 1.33BC. The maximum absorptiometric color reduction occurred at pH 3, with corresponding maximum amounts of iron and hydrogen peroxide. The absorptiometric color and COD reduction were 96% and 57%, respectively. For the oxidation‐coagulation‐photo‐Fenton process, the analyzed variables were pH (A), Fe(VI) concentration (B), H₂O₂ concentration (C), and temperature (D). The regression equation resulting from the quadratic model was η_Abs (%) = 38.3 – 20.2A + 8.12A² – 0.27B + 3.73B² + 0.3C + 3.6C² + 1.67D + 3.1D² + 1.72AB + 0.51AC – 1.82AD + 0.74BC – 1.11BD + 0.03CD. The ANOVA response showed that the highest absorptiometric color reduction occurred at pH 3, with respective maximum amounts of iron and hydrogen peroxide at 60°C. The maximum efficiencies achieved by the proposed treatment process for the trifluraline effluent stream were 95% and 85%, for absorptiometric color and COD reduction, respectively.