Treatment of cadmium and zinc-contaminated water systems using modified biochar: Contaminant uptake, adsorption ability, and mechanism

Cd and Zn contamination in water occurs frequently that threatens water supply, human health, and food production. MnFeB, a novel absorbent biochar modified using KMnO4 and hematite, was prepared and used for the treatment of Cd2+ and Zn2+solutions. MnFeB exhibits a rough surface structure, large specific surface area, higher total pore volume, massive functional groups, and abundant iron oxide, all of which contribute to higher Cd2+ and Zn2+ adsorption capacity. In single metal systems, maximum Cd2+ and Zn2+ adsorption capacities of MnFeB were 1.88 and 1.79 times higher than those of unmodified biochar (CSB). The maximum Cd2+ and Zn2+ adsorption capacities of MnFeB were 2.73 and 2.65 times higher than CSB in the binary metal system. Key adsorption mechanisms of Cd2+ and Zn2+ by MnFeB included electrostatic interaction, co-precipitation, π-π interaction, complexation, and ion exchange. Thus, MnFeB can be used as a novel absorbent to treat Cd and Zn-polluted water.