Heterogeneous Catalyst Of Fenton-like Reaction For Degradation Of Orange Ⅱ

Dye wastewater is a typical refractory organic wastewater which has complicated composition, high color, high organic content, as well as poor biodegradability. It has great harm to the environment. Thus, seeking a cost-effective treatment method to treat dye wastewater has been a difficult problem in the water pollution treatment. Fenton’reaction is a kind of advanced oxidation technology, it has been widely used in the treatment of dye wastewater for its advantages of strong oxidation ability and fast reaction rate. However, the traditional Fenton reaction should be carried out under the condition of strong acid, and the H2O2 utilization of the syetem is very low, a lot of iron sludge were generated after the reaction, even the effluent of water is yellow, causing secondary pollution. The study found that, to some extent, Heterogeneous Fenton reaction can solve the problems existing in the traditional Fenton reaction. Moreover the heterogeneous catalysts have good reusability. Therefore, the heterogeneous Fenton catalyst has a good application prospects. Persulfate activation technologies developed in recent years that based on sulfate radicals (So4·-) is another kind of Fenton-like reaction system. Due to its mild reaction conditions, simple equipment and higl-usage of radical, can even further solve the problems existing in the traditional Fenton reaction, therefore, becoming a another hotspot in the research of Fenton-like system.In this study, persulfate oxidative degradation of Orange II simulated wastewater was studied in the presence of CuFe2O4, CuO and Fe2O3 those prepared by sol-gel combustion method based on citrate complexation. The manufacture condition was optimized, and the optimal prepared catalysts were characterized. The degradation of Orange II with these three catalysts were used to investigate the influenced factors of heterogeneous Fenton-like system. At the same time, analyze the stability of the catalyst to overall evaluate the performance of these three catalysts. The mechanism of persulfate catalyzed by better catalysts were also discussed, attempting to provide a new theoretical basis and technical support to treat dye wastewater by SO4·-.The calcination temperature and time on the effect of catalytic activity were investigated. Experiments showed that the best calcinations condition of CuFe2O4 was calcined at 400℃ for 2h. At this temperature, the best calcination time for CuO and Fe2O3 were also 2h. XRD and EDS results showed that the prepared catalysts were really CuFe2O4, CuO and Fe2O3. SEM and BET analysis showed that CuFe2O4 and CuO were nanoscale. average particle size were 52 nm and 67 nm, respectively. Fe2O3’s average particle size was 139 nm.Initial pH, persulfate dosage, initial Orange Ⅱ concentration were the important factors of heterogeneous Fenton-like by treating Orange Ⅱ. Experiments showed that the degradation effect of CuFe2O4/K2S2O8 reaction system is the highest, CuO/K2s2O8 reaction system is the seconed, while, Fe2O3/K2S2O8 reaction system is the worst.When the reaction conditions were as follows:initial concentration of Orange Ⅱ was 20 mg/L, catalysts concentration was 1g/L, K2S2O8 concentration was 0.5 g/L, the initial pH was 5.3, reaction time were 180 min, the degradation of Orange Ⅱ and TOC removal rate of these three reactive systems were 98% and 62%,97% and 50%,24% and 21%, respectively.The mechanism of persulfate catalyzed by CuO and CuFe2O4 were discussed, coming to the conclusion that the Cu element played an important role during the catalytic process. For CuO, in the acidic condition, homogeneous catalysis of Cu2+ were the main role, heterogeneous catalysis is the supplementary role; increasing the pH to weak acidic or alkaline, heterogeneous catalysis was the mainly role. For CuFe2O4, in the pH range were mainly composed of heterogeneous catalysis, when increasing the initial pH, showing a better degradation effect. Radical quenching tests concluded that the main active intermediates in the reaction system were sulfate radicals and hydroxyl radical, and the main radical species in the acidic condition were sulfate radicals, in the alkaline condition were hydroxyl radical.Stability and reusability analysis of these three catalysts showed that when they were applied to the potassium persulfate reaction system, stability and reusability of CuFe2O4was the best, CuO was the seconed, while, Fe2O3 was the worst. This study shows that CuFe2O4 is a potential heterogeneous catalys for dye wastewater treatment.