Zero-valent iron supported on expanded graphite from spent lithium-ion battery anodes and ferric chloride for the degradation of 4-chlorophenol in water

Abstract

Zero-valent iron supported with expanded graphite (ZVI/EG) were successfully prepared from ferric chloride and the graphite of spent lithium-ion battery (LIB) using carbothermic reduction as a new approach for recycling spent LIB. ZVI/EG composites synthesized with different ZVI mass ratios were used as catalysts for the 4-chlorophenol (4-CP) removal from water by heterogeneous Fenton reactions. ZVI/EG composites showed a BET specific surface area of 11.295 m2 g−1. ZVI/EG synthesized from expandable graphite and ferric chloride with mass ratio of 2:1 (ZVI/EG-2) showed the highest removal percentage of 4-CP, being 97% in 1 h. The degradation rate fitted to a pseudo first-order model better, and reached 0.0527 min−1 for ZVI/EG-2. Moreover, ZVI/EG-2 showed high reactivity for 4-CP removal even in the sixth reuse cycle, being 82%. Hydroquinone and 4-chlorocatechol were identified as the intermediate products of 4-CP degradation. Increasing the ZVI/EG-2 dosage can enhance the 4-CP removal percentage through offering more reactive sites and Fe2+ ions. Acidic pH values favorited the 4-CP removal due to the high H+ concentrations, while Alkaline pH value inhabited the 4-CP removal. A higher temperature increased the rate of •OH formation and enhanced the 4-CP removal percentage. At a fixed dosage of the ZVI/EG-2, the ratio of available reactive sites was less at higher initial concentrations. These results prove the possibility of synthesizing high active and stable ZVI/EG catalysts using graphite from spent LIB and ferric chloride. These catalysts show promising prospective for the 4-CP removal in water, with comparable activities to others previously reported.