Passivation remediation of weakly alkaline Cd-contaminated soils using combined treatments of biochar and sepiolite

Abstract Background Cadmium (Cd) pollution in agricultural soils has become a priority environmental concern globally. A reasonable application of passivators is critical to address the problem. In this study, we examined the remediation effects of rice husk biochar (rBC) and sepiolite (Sep) as single and combined (rBC + Sep) treatments on Cd pollution in a weakly alkaline soil using three maize cultivars (Liyu 16, Zhengdan 958, and Sanbei 218) as test crops. We also explained the mechanisms involved in the remediation effects. Results The pseudo-second-order kinetic equation and Langmuir model could well describe the adsorption process of rBC + Sep for Cd2+. Compared with the control treatment (CK), soil available Cd concentration decreased by 29.51–36.34% under rBC + Sep treatment (p 0.05). Conclusions The application of 0.2% rBC + 0.5% Sep composite passivation material to weakly alkaline Cd-contaminated soil can effectively reduce the Cd concentration of soil and maize.