Enhanced Adsorption Performance of Zn/Co-Modified Biochar for Cu(II) and Cd(II)

This study aims to improve the removal efficiency of heavy metal ions from wastewater. We utilized agricultural residues derived from Camellia oleifera shell and combined them with zeolitic imidazolate frameworks (ZIFs) precursors for synergistic modification. By introducing active components such as Zn and Co in situ using chemical reagents, followed by pyrolysis, co-carbonization, and KOH activation treatments, we prepared nine types of functionalized biochar (BCX-T). Their structural characteristics and adsorption performance toward Cu-(II) and Cd-(II) were systematically characterized. The results showed that BC8-500 exhibited an adsorption capacity of 31.61 mg/g for Cu-(II), a 2.1-fold increase compared to unmodified biochar; BC9-500 exhibited an adsorption capacity of 111.43 mg/g for Cd-(II), a 6.4-fold increase. The adsorption process was primarily driven by chemical adsorption and multilayer adsorption. The removal of Cu-(II) by BC8-500 was mainly achieved through complexation, whereas the removal of Cd-(II) by BC9-500 was primarily achieved through CdCO₃ precipitation. This study provides a theoretical basis for the effective utilization of agricultural and forestry residues, as well as for the mitigation and management of environmental pollution.