Catalytic wet oxidation of the pretreated synthetic pulp and paper mill effluent under moderate conditions

In the present study, catalytic wet oxidation (CWO) was investigated for the destruction of organic pollutants in the thermally pretreated effluent from a pulp and paper mill under moderate temperature and pressure conditions. The thermal pretreatment studies were conducted at atmospheric pressure and 368 K using copper sulfate as a catalyst. The thermal pretreatment reduced COD by about 61%. The filtrate of the thermal pretreatment step was used at pH 8.0 for CWO at 383–443 K temperature and a total pressure of 0.85 MPa for 4 h. Catalysts used for the reaction include copper sulfate, 5% CuO/95% activated carbon, 60% CuO/40% MnO2, and 60% CuO/40% CeO2. Maximum COD reduction was found to be 89% during CWO step using 5% CuO/95% activated carbon with a catalyst loading of 8 g l−1 at 443 K and 0.85 MPa total pressure. Overall COD reduction for the pretreatment and the CWO was found to be 96%. Besides this, 60% CuO/40% CeO2 catalyst also exhibited the similar activity as that of obtained with 5% CuO/95% activated carbon catalyst at 423 K temperature and 0.85 MPa total pressure. The pH of the solution during the experimental runs decreases initially due to the formation of carboxylic acid and then increases due to the decomposition of acids.