Performance of sludge-based activated carbon to remove COD from mature landfill leachate: the influence of carburant and activator

This paper describes the preparation of several sludge-based activated carbons (SACs) from sewage sludge with different carburants and activators. A comparative study of COD removal efficiency from the mature leachate by different SACs, and the effects of different carburants and activators on the COD removal performance of SACs are discussed. The results show that COD removal efficiency from the mature leachate by the prepared SACs reaches 72.06% to 85.61%, and the adsorption process was composed of monolayer adsorption and multilayer adsorption, with predominantly multilayer adsorption. The best performance in adsorption efficiency was given by the SAC prepared by using corn stalks as the carburant and ZnCl2 as the activator: a dosage of 2%, adsorption time of 40 min, and pH = 4, led to a COD removal efficiency of 82.25%. Corn straw as the carburant was more positively significant in improving the adsorption performance of SACs: the surface of that SAC was dominated by basic functional groups, and a larger q L of 227.27 mg/g was obtained, which is 3.68 times that of the SAC prepared with Brassica oleracea as the carburant. From the perspective of the activator, ZnCl2 had the best activation effect. Though SAC prepared with K2CO3 as its activator obtained the largest q L of 231.05 mg/g, the apparent adsorption rate was slow, and the adsorption time was much longer than those of the SACs prepared with ZnCl2 and KOH.