Recovery of Valuable and Hazardous Metals (Ni, Co, and Cd) from Spent Ni–Cd Batteries Using Polyvinyl Chloride (PVC) in Subcritical Water

Abstract

In recent years, recycling of waste Ni–Cd batteries has drawn substantial attention due to the severe environmental pollution they cause and to avoid the dissipation of valuable metals. Although a considerable amount of research has been conducted, efficient recycling of valuable and hazardous metals from waste Ni–Cd batteries through an environment-friendly and economical process is still a challenge. The present study focuses on leaching of valuable and hazardous metals from waste Ni–Cd battery powder via a PVC-assisted subcritical water extraction method. The effects of various factors, such as time, temperature, liquid/solid ratio, and mass ratio (PVC:Ni–Cd battery powder), on the recovery efficiencies of Ni, Cd, and Co are also investigated. After metal extraction, the solid residues were analyzed by XRD, XPS, FT-IR, FE-SEM, and EDS element mapping to anticipate the chemical compounds before and after the recycling experiment. Meanwhile, ICP-OES analysis was used to determine the metal content in the leachate. The ICP-OES results showed that more than 96.38, 92.98, and 99.96% of Ni, Cd, and Co, respectively, were satisfactorily recovered from the waste Ni–Cd battery powder under the optimized conditions: 300 °C temperature, 120 min reaction time, 15 mL/g liquid/solid ratio, and 1:3 Ni–Cd battery powder:PVC mass ratio. The results obtained from this study suggest that the applied subcritical water extraction could be an efficient, environment-friendly, and sustainable technology for the recovery of valuable and hazardous metals from waste Ni–Cd batteries.