Degradation kinetics of azo dye, Acid Blue 161 (AB161), by Fenton and photo-Fenton processes in aqueous solution was investigated. At pH 3.5, the effects of H2O2, Fe2+, and H2O2/Fe2+ molar ratios, on the AB161 decolorization kinetic rates, were evaluated. Experimental results confirmed that the optimal H2O2/Fe2+ molar ratio of 12 is close to the theoretical value of 11 as predicted by previously developed model. The influence of azo bond loading (L azo bond), from 0.25 to 1.0, and pH values from 2.5 to 4.0 were evaluated on AB161 decolorization kinetic rates. A correlation between the natural logarithm of the decolorization rates and L azo bond was established at the different pH values. The decolorization rate increased linearly with decreasing L azo bond, in the order of pH: 3.5 > 3.0 > 2.5 > 4.0. UV radiation of Fenton processes increases degradation of AB161 more than 40 % due to the regeneration of Fe2+ through photo-catalytic reactions. This phenomenon was confirmed by measuring H2O2 concentration during the photo-Fenton processes. The results suggest that Fenton processes can effectively decolorize or degrade wastewater containing azo dye, AB161. Photo-Fenton processes may further increase the degradation efficiency of AB161 by 40 %.

Background and purpose: Paraquat (PQ) is a bipyridinium herbicide that is very soluble in water. This non-selective contact herbicide is widely used in agriculture for weed control. In addition to the environmental impact, paraquat affects the entire body, especially the respiratory system, central nervous system and lymph nodes. In this study degradation of paraquat was investigated using Fenton and Fenton like processes.Materials and methods: This research was an experimental study in laboratory scale batch reactor (1L). During these processes, the effects of pH, Fenton and Fenton like agent concentrations (Fe2+, Fe3+ and H2O2) and initial concentration of paraquat in the removal efficiency were studied. The residual PQ concentration and the amount of organic carbon removal were measured by HPLC (259nm) and TOC measurement device, respectively.Results: Fenton like and Fenton processes could remove 86.44% and 84.53% of paraquat under optimal condition (pH=3, H2O2=29.4 mM, Fe=0.9 mM, PQ=0.194 mM) in 120 minutes, respectively. The TOC removal in Fenton like and Fenton processes was 52.15% and 45%, respectively. The PQ removal by Fenton and Fenton like process followed a pseudo-first order reaction kinetic model.Conclusion: Fenton process showed better performance in removal of PQ than Fenton process. So, it can be used as an appropriate and a supplementary treatment process in removing PQ from aqueous solution or final purification in a longer reaction time.

Background: Fenton (Fe2+and H2O2) and modified Fenton (Fe3+and H2O2) are two popular methods used in advanced oxidation processes (AOP) and degradation of persistent organic pollutants (POPs), such as dye compounds. In these processes, Fe2+and Fe3+as catalysts and H2O2 as the oxidizing agent are added to the reactor.Objectives: The aim of the current study is to assess the abovementioned methods for removal of Reactive Red 198 and Blue Reactive 19 from aqueous solutions.Materials and Methods: This research was carried out using lab-scale. After preparation of RB-19 and RR-198 stock solutions (1000 ppm), optimum pH and temperature were determined within the range of (3-11) and (15oC-40oC) respectively, and specific amounts of Fe2+ and Fe3+ (0.8, 1, 3, 7, 14 and 32 mM) were prepared by adding FeSo4.7H2O and FeCl3, and H2O2 30% W/W (2, 5, 11, 23, 47 and 94 mM) were added to the solutions to establish the H2O2/Fe2+, Fe3+molar ratios. Standard jar tests were conducted using jar test apparatus. After sedimentation time, samples were filtered through a 0.45 mm fiber membrane, and then final dye concentrations were measured using a UV/VIS spectrophotometer.Results: The highest dye removal efficiency in both Fenton and modified Fenton methods were obtained at the optimum pH=3, optimum reaction time of 10 minutes, optimum temperature at 25oC and H2O2/Fe2+and H2O2/Fe3+concentrations of 11.3 and 5.1 mM, respectively.In the Fenton reaction the maximum efficiency was obtained at 94.70% and 99.31% for reactive red 198 and reactive blue 19, respectively.Moreover, by the modified Fenton method the maximum removal efficiency for reactive red 198 and reactive blue 19 was 94.8% and 99.43%.Conclusions: Fenton and modified Fenton processes could be used as very effective methods for removal of reactive red 198 and blue reactive 19 from aqueous solutions.

Background: The growth of population, improvement of quality of life and the development of industries have led to increase in the rate of urban and industrial waste. As the leachate of the waste has a lot of pollution, influences harmfully human health and the environment. Researches have shown that the advanced oxidation processes (AOPs) such as Fenton and Fenton-related processes can reduce chemical oxygen demand (COD) of the leachate effectively.Materials and Methods: In this paper, the rate of decrease in the total suspended solids (TSS) of leachate from a composting facility in Isfahan was studied using electrochemical, Fenton and electro- Fenton processes. These processes were conducted at reaction times 0, 20, 40, and 60 minutes, with the currents of 0.5, 1 and 1.5A and hydrogen peroxide dosages 1000, 2000, and 3000 mg/L.Results: In the three mentioned processes, the most TSS removal was observed at the first 40 minute of the reactions. Among the studied processes, the electro-Fenton removed up to 92.4% of the TSS and was recognized as the most effective method. Furthermore, electrochemical and Fenton removed 41.7% and 60.3% of the TSS, respectively.Conclusion: Therefore, decreasing the TSS of leachate could change its qualities and reduce the leachate pollution and the adverse environmental effects.

In this project decolorization and mineralization of synthetic wastewater containing acid red 33 (AR33) was investigated by Fenton and photo Fenton processes in a batch photo reactor. A comparative assessment using Fenton and photo Fenton processes was performed after initial optimization studies such as varying pH, the concentration of pollutant, peroxide and iron. The color removal and mineralization efficiency of AR33 were calculated by Spectrophotometric and chemical oxygen demand (COD) tests. The degradation efficiency in photo Fenton process (98.5% in 10 min of reaction) was higher than Fenton ones (97.5% in 30 min). After 60 min of reaction, the removal of COD in photo Fenton and Fenton processes was 71% and 37.5%, respectively. Therefore, photo Fenton was the most effective process in partial mineralization of AR33. Kinetic constants were evaluated using pseudo first order equations to obtain the rate constant, K.

This research used the Fenton-like oxidation method to decompose the cationic and anionic resins. Acid digestion and the fenton method were also studied to compare the results. Acid digestion and Fenton methods did not show desirable results, so the research was focused on Fenton like process. For this purpose, Cu 2+ was used as a catalyst and H2O2 as an oxidant. Five parameters including temperature, pH, Cu2+ concentration, H2O2 addition flow rate, and time were studied to obtain the optimum value for the decomposition of fresh resin. It was found that the optimum values were as follows: temperature: 75,C, Cu 2+ concentration: 0. 3 M, H2O2 addition flow rate: 0. 5 ml/min for cationic and 0. 25 ml/min for anionic resin, and time: 2 hours. By optimization of the parameters decomposition weight percent of 88% was obtained for cationic resin and 83% for anionic resin. The optimum condition was applied for the actual sample, a mix of cationic and anionic resin from the Tehran research reactor. The decomposition percent of 81% was achieved. The resins were characterized before and after decomposition by FTIR and SEM, which showed the decomposition. COD analysis showed that only 2% of decomposed resin was maintained in the solution, and 98% was converted to CO and H2O.

In this study, Chemical Oxygen Demand (COD) from a pharmaceutical wastewater (PhW) was reduced by several techniques such as electro-Fenton (EF), photo electro-Fenton (PEF) and activated sludge (AS) processes and the obtained data were compared with each other. The effects of several parameters such as pH, current density, H2O2/Fe2+ molar ratio, volume ratio of H2O2/PhW, reaction time and UVA light were studied on the COD reduction through the EF and PEF processes. The Box-Behnken Design (BBD) under Response Surface Methodology (RSM) was applied to design and then optimize these processes. The optimal conditions for 87% of COD removal through the EF process were at pH of 3. 27, current density of 57 mA/cm2, H2O2/Fe2+ molar ratio of 3. 5, volume ratio of H2O2/PhW of 1. 34 ml/l and reaction time of 56. 32 min while the optimal conditions for 91. 6% of COD removal through PEF process were at pH of 3. 5, current density of 57. 5 mA/cm2, H2O2/Fe2+ molar ratio of 3. 81, volume ratio of H2O2/PhW of 1. 5 ml/l, reaction time of 10. 12 min and 6 W UVA light while 77. 70% of COD removal was obtained by the AS process with residence time of 1020 min. According to the kinetic study, the second order reaction (with high R2 data) could properly model the EF and PEF processes.