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

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 degrees 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.