Sulfur-modified Pleurotus ostreatus spent substrate biochar enhances the removal of cadmium in aqueous solution: Characterization, performance, mechanism

Cadmium (Cd) is a toxic metal element that adversely affects water bodies and poses a threat to the ecological environment and human health. In this experiment, Pleurotus ostreatus spent substrate (P) was used as the initial material to prepare Pleurotus ostreatus spent substrate biochar (PB) at a high temperature of 500 C, and then modified with CS2 and NaOH to obtain sulfur-modified Pleurotus ostreatus spent substrate (SP) and sulfur -modified Pleurotus ostreatus spent substrate biochar (SPB) to remove Cd(II) in aqueous solution. The adsorp-tion of Cd(II) on the four materials follows the Langmuir isotherm model and the pseudo-second-order kinetic model. After modification with sulfur, the specific surface area and pore volume of both modified materials were significantly increased, and the adsorption capacity for cadmium was enhanced. The equilibrium adsorption capacity of SPB was 55.9636 mg g-1, and the maximum adsorption capacity of SPB was 443%, 369% and 229% of that of P, SP and PB, respectively. Single factor batch adsorption experiments and characterization results showed that the adsorption of cadmium on SPB was mainly due to the interaction of cadmium and organic sulfides, the precipitation of cadmium hydroxide and carbonate, and the formation of Cd-C pi bonds.