Removal of organic matter from wastewater using M/Al-pillared clays (M = Fe or Mn) as coagulants

Investigation of the deactivation and regeneration of an Fe2O3/Al2O3•SiO2 catalyst used in catalytic ozonation of coal chemical industry wastewater

Catalyst deactivation is an ongoing concern for industrial application of catalytic ozonation processes. In this study, we systematically investigated the performance of a catalytic ozonation process employing Fe₂O₃/Al₂O₃•SiO₂ catalyst for the treatment of coal chemical industry (CCI) wastewater using pilot-scale and laboratory-scale systems. Our results show that the activity of the Fe₂O₃/Al₂O₃•SiO₂ catalyst for organic contaminant removal deteriorated over time due to formation of a dense and thin carbonaceous layer on the Fe₂O₃ catalyst surface. EPR and fluorescence imaging analysis confirm that the passivation layer essentially inhibited the O₃-catalyst interaction thereby minimizing formation of surficial ^•OH and associated oxidation of organic contaminants on the catalyst surface. Calcination was demonstrated to be effective in restoring the activity of the catalyst since the carbonaceous layer could be efficiently combusted during calcination to re-establish the surficial ^•OH-mediated oxidation process. The combustion of the carbonaceous layer and restoration of the Fe layer on the surface on calcination was confirmed based on SEM-EDX, FTIR and thermogravimetric analysis. Cost analysis indicates that regeneration using calcination is economically viable compared to catalyst replacement. The results of this study are expected to pave the way for developing appropriate regeneration techniques for deactivated catalysts and optimising the catalyst synthesis procedure.