Nitrogen and sulfur co-doped biochar derived from peanut shell with enhanced adsorption capacity for diethyl phthalate

Doping of nitrogen and sulfur on biochar (NS-B) was investigated by a novel and improved method for diethyl phthalate (DEP) removal. The preparation parameters including pyrolysis temperature and size of peanut shell biochar as well as thiourea/biochar mass ratio were selected as independent variables at three levels by applying the Box-Behnken design. The ANOVA results indicated that thiourea/biochar mass ratio exhibited the most significant effect. The comprehensive effects of the three factors on DEP removal efficiency were further elaborated, combining with the characterization results of the obtained NS-B materials. The formation of the pyridinic N and oxidized S groups examined by XPS was responsible for enhancing the DEP removal efficiency. The adsorption kinetic model fitting illustrated that large micropores and numerous adsorption sites improved the adsorption capacity of NS-B. According to the adsorption isotherm model fitting, NS-B (temperature 375 °C, size 300 mesh and thiourea/biochar mass ratio 0.1) possessed much higher maximum adsorption capacity for DEP (14.34 mg g−1) than biochar (6.57 mg g−1). NS-B exhibited excellent reusability towards DEP removal after five times recycling. Moreover, NS-B also had the potential in peroxydisulfate activation. These findings provide new insights into the environmental implications of NS-B.