Upcycling spent Ni–Cd battery for selective synthesis of nanoparticles to harness into electro-conductive thin films: An eco-friendly approach for e-waste management

Abstract

Inspired by Sustainable Development Goal-12 (responsible consumption and production) to reduce e-waste, an environment friendly extraction of Cd, Ni and Co from Ni–Cd spent batteries have been reported here using ammonium chloride as a chlorinating agent for the first time. Multiple parameters i.e. dose of chlorinating agent, roasting time, and temperature has been optimized that resulted in extraction of 99.93 % Cd, 90.1 % Ni and 84.81 % Co. Metal enriched leachate was then subjected to unique precipitation steps that resulted in synthesis of Cd nanoparticles, Co3O4·NiO composite nanoparticles, and NiO nanoparticles, characterized through XRD and FESEM-EDX. Synthesized nanoparticles were further employed in the fabrication of electro-conductive nano thin films via Layer by Layer (LbL) technique. Film buildup of six novel architectures was monitored using an Ellipsometer. Homogenous film growth was tailored by optimizing ratio, concentration and dipping time of nanoparticles and polymer solutions. Conductivity studies revealed that imbedding synthesized nanoparticles impart significant conductive behavior in thin films with maximum conductivity of 1.8 × 10−4 S/cm, in addition to exhibiting appreciable resistance against 0.1 M HCl, 0.1 M NaOH and acetone. Contact angle and AFM images revealed that the films were slightly wettable and homogenous respectively. Conclusively not only Cd, Ni and Co were successfully recycled from Ni–Cd spent batteries employing greener technique but were also harnessed into robust nano-thin films with focus towards electro-conductivity based applications.