Activated carbon preparation from pyrolysis char of sewage sludge and its adsorption performance for organic compounds in sewage

Abstract

Although sludge pyrolysis has been extensively studied in sludge disposal, it is challenging to utilize sludge pyrolysis products. Here, we report a method for preparing sludge activated carbon (SAC) by activating sludge pyrolysis carbon by zinc chloride. The effect of ZnCl2 concentration, activation temperature and activation time on the activated carbon were investigated. The prepared activated carbons were characterized by thermogravimetric analysis, thermal kinetics analysis, Fourier transform infrared spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and N2 adsorption-desorption. The results show that when the ZnCl2 concentration was 8 mol/L with an activation time of 1 h at an activation temperature of 800 °C, the SAC iodine adsorption value and methylene blue adsorption value were 816.27 mg/g and 95.25 mg/g, respectively. The SAC exhibited a high BET surface area (up to 765.88 m2/g). The experimental results for simulated wastewater adsorption by SAC prepared under the above preparation conditions show that at an initial concentration of dimethyl phthalate (DMP) of 30 mg/L, addition amount of SAC of 20 mg, adsorption time of 30 min and temperature of 25 °C, the removal ratio of DMP can reach 87%. According to the data obtained, sludge pyrolysis char is a suitable precursor for activated carbon preparation. The obtained SAC could be used as a low-cost adsorbent with favorable surface properties.