Microwave activated persulfate oxidation of leachate subsequent to optimized chemical coagulation

Abstract

In this study, a chemical coagulation process in which alum and poly aluminum chloride (PAC) were used as coagulants were applied to the leachate and the process operating conditions were optimized with the response surface method and Box-Behnken design. Operating parameters of the chemical coagulation process were coagulant dose, initial pH, and reaction time while COD and UV254 removal were model responses. The COD removal obtained statistically under the optimum conditions determined by the model was 58.1% and 54.2% for alum and PAC, respectively. The experimental COD removal efficiencies were 56.9% and 50.8% for alum and PAC, respectively. Based on the results of the coagulation process, alum was selected as the coagulant. As a second step, persulfate oxidation activated by the microwave method was applied to the leachate. The effect of initial pH, microwave power, reaction time, and PS dose on COD and UV254 removal by persulfate oxidation was determined using the conventional optimization method. The COD and UV254 removal obtained in 3 min reaction time under the conditions of microwave power 450 W, pH 5, and 5 g/L persulfate dose was 51.7% and 55.4%, respectively. As a result of the combined coagulation and oxidation process, a total of 79.2% COD removal and 92.1% UV254 removal from leachate was provided.