Preparation of efficient and economical adsorbent for Cu2+ and Pb2+ adsorption via modifying the silicon–oxygen structure of leaching residues

One eco-friendly and cheap cost leaching residue (LR) was obtained from serpentine leaching system and used to adsorb Cu2+ and Pb2+ in wastewater. LR had a large specific surface area, and uneven interface with irregular holes provided more adsorption sites. Moreover, silicon–oxygen structure of LR presented as one bridge oxygen (Q1), which was more electronegativity and act as the adsorption active site for metal actions. All these characteristics indicated that LR had good adsorption performance, whose equilibrium adsorption capacity (Qe) for Cu2+ and Pb2+ could reach to 38.85 and 27.97 mg/g, respectively. Moreover, the Qe of Pb2+ was much lower than that of Cu2+ in single or binary systems. Selective adsorption mechanism was studied by DFT calculations, the adsorption energy (Eads) of Si–O–Cu and Si–O–Pb equaled to −2.4834 and −2.1822 Ha, indicating that the interaction of Cu2+ ions with LR was stronger and more stable than Pb2+ ions. In this work, leaching residue was transformed into an efficient and cheap absorbent via modifying the silicon–oxygen structure of clay minerals.