Adsorption performance of food waste biochar for Cu²⁺， Zn²⁺， and Pb²⁺

To effectively address the issue of heavy metal contamination in aquatic ecosystems， this study employed food waste （FW） as the raw material to produce food waste biochar （FWB） through pyrolytic carbonization. The adsorption performance of FWB for Cu²⁺， Zn²⁺， and Pb²⁺ was examined. In a single-metal system， the adsorption capacities of FWB for Cu²⁺， Zn²⁺， and Pb²⁺ were 40.283 mg/g， 37.082 mg/g， and 51.565 mg/g， respectively. Compared with the single heavy metal system， the adsorption performance of FWB was found diminished in the multi-metal system， which was attributed to the competitive adsorption reaction between the ions. The order of adsorption preference of FWB for the heavy metals was determined to be Cu²⁺ > Pb²⁺ > Zn²⁺. Based on the aforementioned characterization， the adsorption mechanism of FWB for the three heavy metals was inferred to include complexation with oxygen‑containing functional groups， ion exchange， and carbonate precipitation. Notably， the adsorption mechanism of Ca in FWB for Cu²⁺ differed from that for the other two heavy metals： Ca complexed with Cu²⁺ to form a Cu-containing precipitation structure， whereas ion exchange primarily occurred between Ca and Zn²⁺ and Pb²⁺.