Preparation Of Cu-based Hydrotalcite And Its Catalytic Activity In Wet Oxidation

In the study, the research progress on the highly concentrated organic compounds wastewater treathment was reviewed. The preparation, characterization,mechanism of the precursor CuMg Al O catalysts were systematically studied. The effect of catalytic wet peroxide oxidation reaction conditions on the performance of the catalysts was studied. The catalytic performance and stability of the Cu MgAl LDH type catalyst was studied, meanwhile, the possible pathway of the degradation of the Methyl orange was studied. Moreover, the relationship between the structure of the Cu Mg AlO catalysts and the catalytic activity was studied. So the research on new high-efficiency catalysts to treat difficult degradation organic matter with CWPO is imperative.Firstly, Cu MgAl LDH was synthesized by using impregnation method with “structure memory effect”. The properties of CuMg Al LDH were characterized via XRD、FT-IR、SEM、TG-DTA and EDS. Compared with the Mg Al LDH, the thickness of the Cu MgAl LDH layer increased, the degree of crystallinity of the Cu Mg Al LDH reduced and the thermal stability declined. The mechanism of the Cu Mg Al LDH formation was discussed, the results showed that its mechanism can be summed up as dissolution-precipitation-diffusion mechanism.Next, the processing parameters of the methyl orange degradation with Cu Mg AlO500 were optimized in the CWPO. The Cu MgAlO500 catalysts showed the better activity(above 95%) under the conditions of temperature 50°C, reaction time 120 min, dosage of H2O2 6 mL, catalyst loading of 1.5g·L-1 and pH 6. And, the response surface analysis indicated that the predicted optimum decolorization efficiency of methyl orange was above 99% under the conditions of 120 min, 1.5 g·L-1 CuMg Al O500, temperature 55 oC, dosage of H2O2 6 mL and pH value 6.And again, the catalytic performance and stability of the Cu MgAl LDH type catalyst was studied.The results showed that the highest decolorization efficiency of methyl orange reached 99.7% by the CuMg AlO catalyst with 2:1 of Mg/Al molar ratio, cacliation temperature 500 oC and Cu2+ concentration of 0.01 mol·L-1, respectively. At the end of the reaction, the loss amount of copper was 3.4 mg·L-1. The decolorization mechanism of methyl orange was investigated by FT-IR、UV-Vis and GC-MS. The results showed the conjugated structure of methyl orange was cracked firstly, and its product were a series of single benzodiazepines intermediate. And the benzodiazepines intermediate was further decomposed.Finally, CuMg AlO type catalyst was synthesized by using impregnation and “structure memory effect” method. The properties including surface area, crystal phase composition, surface profile, and reducibility of the catalysts were characterized by XRD, SEM, BET and H2-TPR. The catalytic activity for CWPO of methyl orange was investigated. Moreover, the relationship between the surface structure and the catalytic activity was studied. The results showed that the Cu of Cu Mg AlO type catalyst using “structure memory effect” method was highly dispersed into Mg AlO and the it had lower reduction temperature and high reactivity. Nearly 100% decolorization efficiency was achieved in CWPO of methyl orange at 55 oC, dosage of H2O2 6 mL and catalyst loading of 1.5 g·L-1.