Synergistic decontamination mechanisms of copper smelting slag-derived Fe-Al oxides/biochar composite for Cu-Ni Co-contaminated systems

Abstract

Cu(II) and Ni(II) are common toxic heavy metals in water, posing significant risks to both ecosystems and human well-being. A novel magnetic adsorbent, CBS700, was synthesized using industrial copper slag and biomass waste to treat wastewater contaminated with Cu(II) and Ni(II). The heavy metal removal process adhered to the pseudo-second-order kinetic model and the Langmuir isotherm model. CBS700 exhibited maximum adsorption capacities of 135.15 mg/g for Cu(II) and 133.87 mg/g for Ni(II) at the optimal pH. Competitive adsorption was observed during the removal of Cu(II) and Ni(II). CBS700 primarily adsorbs Cu(II) and Ni(II) through six mechanisms: physical adsorption (pore filling), surface complexation (Al-O, Fe-O, and -OH groups), cation exchange (Ca²⁺, K⁺, Mg²⁺, and Na⁺), hydrogen bonding (-OH, CC, CO, C-O, Al-O, and Fe-O), oxidation, and precipitation. The influence of various components on the adsorption energy (E_ads) of Cu(II) and Ni(II) followed the order: Fe-O > Al-O > -OH > pristine biochar. With a saturation magnetization of 18.92 emu/g, CBS700 can be efficiently separated from wastewater. This research introduces an innovative and efficient approach for treating wastewater contaminated with Cu(II) and Ni(II), alongside the novel resource utilization of copper slag.