Pore-expanded core-shell adsorbent for high Cu(II) adsorption: Performance and DFT mechanism

The treatment of copper laden wastewater, particularly from the electroplating industry with the Cu(II) ion concentration ranging from 100 to 300 mg/L, presents a significant challenge for achieving stringent discharge standards. This study reports the synthesis of a pore-expanded core-shell adsorbent with remarkable Cu(II) adsorption performance, accompanied by the electronic-scale investigation of its structure and behavior. This kind of adsorbent both enhances mass transfer and provides abundant chelating sites. It showed superior adsorption performance (122.55 mg/g at 318 K) which originates fundamentally from the electronic heterogeneity of its interfacial coordination environments. By integrating density functional theory (DFT) calculations with X-ray photoelectron spectroscopy (XPS), we systematically decouple the roles of distinct adsorption sites and quantify their electronic interactions with Cu(II). DFT reveals a broad distribution of adsorption energies (−1.650 to −5.989 eV) across three primary coordination modes. Our findings demonstrate that the high adsorption capacity stems from the coexistence of multiple site types: stable multidentate sites enable high metal loading, while electronically active sites with strong charge transfer ability facilitate rapid kinetics. Beyond the specific application, the synergistic strategy of pore-expanded structure and the atomic-scale mechanistic understanding established provide a paradigm for the rational design of advanced adsorbents.