Copper Slag Resource Utilization: Synthesis of Nano-Zero-Valent Iron (nZVI) and Its Efficient Application in Arsenic Removal from Smelting Wastewater

Arsenic contamination presents a serious risk to both ecosystems and human health worldwide. Adsorption has emerged as an economical and effective method for treating arsenic‑laden wastewater. In this study, a nano‑zero‑valent iron adsorbent (CS‑nZVI‑PVP) was prepared using leachate from industrial copper slag as the iron source, and the effect of polyvinylpyrrolidone (PVP) addition on the adsorbent’s morphology and adsorption performance was systematically investigated. Batch experiments demonstrated that CS‑nZVI‑PVP achieved an arsenic removal efficiency of 99.64% with a maximum adsorption capacity of 1066   mg/g, reaching equilibrium within 45   min. Analysis of adsorption isotherms, kinetics, and thermodynamics indicated that the adsorption process follows a multilayer model and is spontaneous and endothermic. The adsorbent also exhibited excellent reusability, maintaining high performance over five consecutive adsorption–regeneration cycles. Mechanistic studies revealed that arsenic removal proceeds through the synergistic actions of surface complexation, electrostatic attraction, and coprecipitation. This work not only advances the resource‑oriented utilization of industrial waste but also offers an efficient and low‑cost strategy for designing adsorbents to remediate arsenic‑contaminated water.