Enhancing cadmium removal efficiency through spinel ferrites modified biochar derived from agricultural waste straw

Water pollution caused by heavy metals poses a serious threat to the ecological environment and human health, which requires the exploration of efficient, economical and convenient methods to solve such urgent problems. In this work, agricultural waste straw was prepared and modified by spinel bimetal through sol-gel method to obtain novel MnFe2O4 loaded biochar with the purpose of efficiently cadmium (Cd) removal from water. Results showed that the as-prepared composites showed much higher Cd adsorption capacity as compared to the original biochar (127.37 vs 25.73 mg/g). Further investigation showed that the integrity of crystal plane structure contributes to the appearance of net-like pore and the 18-fold enlarged specific surface area. Strong anti-interference ability of the spinel loaded biochar was observed in binary and quaternary systems through adsorption affinity investigation using separation factor (αMetalCd, Metal=Pb, Zn, Cu). Due to its magnetic properties, the adsorbent was easily separated and recovered from aquatic solutions, and the adsorption capacity showed little decrease after five cycles. This work provided the references for resource utilization of agricultural wastes and its application in wastewater treatment.