Using oiltea camellia shells, a typical agricultural waste, in Hunan as feedstock, Na2SiO3 solution was used to impregnate oiltea camellia shells and modified biochar was prepared under oxygen-limited conditions. We have studied the adsorption efficiencies of Cd in solution by different biochars and the resistance efficiencies of Cd activity in soil by biochars coupled with flooding. Scanning electron microscopy, Brunauer-Emmett-Teller analysis, and Fourier transform infrared spectroscopy were used to reveal the physicochemical properties of the biochars. The results showed that compared with the camellia oil shell biochar, the modified camellia oil shell biochar (MBC) obtained more special surface areas and functional groups, which showed stronger adsorptive capacities for Cd. A waterlogging soil incubation experiment showed that flooding could simultaneously increase the soil pH values and decrease the acid-soluble Cd component. More available Cd was transformed into the residual state as the flooding time increased, and biochar addition coupled with flooding could lead to further improvement of acid-soluble Cd transformation to the residual state and reduce the acid-soluble Cd content. The concentration of acid-soluble Cd was significantly negatively correlated with the increase in biochar dosage. At 60 d of flooding, the acid-soluble Cd content was 0.33 mg·kg-1 (a decreased amplitude of approximately 45.0%) in 5.0% additional of MBC disposal. Thus, sodium silicate-modified biochar is a novel and effective material for the remediation of Cd-contaminated water and soil, and the research results provide a reference for the resource recovery of Camellia oleracea organic waste.
Keywords: Cd formation; additive amount; flood experiment; modification with sodium silicate; oiltea camellia shells.