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.     

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.     

Glutamic Acid Modified Fenton System for Degradation of BTEX Contamination

The present study employed a modified Fenton system that aims to extend the optimum pH range towards neutral conditions for studying the oxidation of benzene, toluene, ethyl benzene, xylenes (BTEX) using glutamic acid (Glu) as an iron chelator. Addition of 20 mM Glu greatly enhanced the oxidation rate of BTEX in modified Fenton system at pH 5–7. A rapid mass destruction (>97% after 1 h) of BTEX as a water contaminant carried out in the presence of 500 mM H₂O₂, 10 mM Fe²⁺, and 20 mM Glu at pH 5 could be shown. The efficiency of this modified Fenton's system for mass destruction of BTEX in contaminated water was measured to estimate the impact of the major process variables that include initial concentrations of soluble Fe, H₂O₂, Glu (as metal chelating agent), and reaction time.     

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.     

Degradation of Disperse Blue E‐4R in Aqueous Solution by Zero‐Valent Iron/Ozone

Degradation of an anthraquinone dye, disperse blue E‐4R, by zero‐valent iron (ZVI)/ozone (O₃) was carried out in a series of laboratory‐scale experiments. The obtained results indicated that this method was much more effective than single ZVI or single O₃ at removal of color, chemical oxygen demand, total organic carbon, and adsorbable organic halogen. The effect of several related operational parameters, including O₃ dosage, zero valent iron dosage, temperature, pH value, and ZVI particle size were also discussed. Finally, we tried to decontaminate some actual samples with this method, which showed high treatment efficiency to the sample pretreated by conventional activated sludge.     

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.     

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.     

Carbamazepine Removal from Groundwater: Effectiveness of the TiO2/UV,Nanoparticulate Zero‐Valent Iron,and Fenton (NZVI/H2O2) Processes

Pharmaceutical compounds, widely produced and used all around the world, are partly responsible for the widespread water pollution in the environment. Carbamazepine (CBZ) is an antiepileptic drug that persists in the environment for many years. In the present study, we used the TiO₂/UV, nanoparticulate zero‐valent iron (NZVI), and NZVI/H₂O₂ treatment processes to compare efficiency of CBZ removal from water. Influence of NZVI loading, H₂O₂ concentration, TiO₂ loading, UV lamp power, and the matrix (distilled water and groundwater) on CBZ removal efficiency was evaluated using full factorial design. Results indicated that the NZVI/H₂O₂ process oxidized CBZ within 5 min. On the other hand, the NZVI process alone did not reduce CBZ concentration after 120 min of process time. The NZVI/H₂O₂ process was equally effective in CBZ removal from both distilled water and groundwater whereas the TiO₂/UV process was less effective due to the presence of ions in groundwater. CBZ removal efficiency of the TiO₂/UV process declined 30% when the matrix was changed from distilled water to groundwater. Negative divalent ions, i.e., and , were the main cause of reduction of CBZ removal efficiency from groundwater. It is likely that these two ions adsorb onto, and consequently prevent the superoxide anion and hydroxyl radical OH^? from being generated on, the surface of the TiO₂.