ZnCl2 modified biochar derived from aerobic granular sludge for developed microporosity and enhanced adsorption to tetracycline

In this study, biochar derived from aerobic granular sludge was modified by ZnCl2 (Zn-BC) to improve the adsorption performance of tetracycline (TC). The surface area, pores, and functional groups of Zn-BC were characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area, Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) and the effects of initial pH, TC concentration, and temperature on TC adsorption performance were analyzed. At the same time, the adsorption kinetics, isotherms, thermodynamics and diffusion models were studied. The results showed that the BET surface area and micropore volume of Zn-BC were 852.41 m2·g-1 and 0.086 cm3·g-1, respectively. The maximum adsorption performance of TC was 93.44 mg·g-1, and it was less influenced by pH. The adsorption of TC on Zn-BC agreed well with the pseudo-second-order model and the Langmuir isotherm. The thermodynamic parameters indicated that the adsorption process was a spontaneously endothermic reaction.