Sustainable Process to Recover Metals from Waste PCBs Using Physical Pre-Treatment and Hydrometallurgical Techniques

Abstract

Printed Circuit Boards (PCBs) are an essential component of electronic devices. The digitalization and upgrading of gadget generates lots of PCB-containing electronic waste. Conserving resources and protecting the environment requires the recycling of such e-waste. This paper focuses on the recovery of metals from waste PCBs using physical pre-treatment and hydrometallurgical processes. Initially, the waste PCBs were pre-treated and beneficiated to separate the metallic and non-metallic fractions. The metallic concentrate obtained was leached using nitric acid (a strong oxidative agent) to dissolve the metals. The system was fully jacketed with a scrubber and condenser to prevent the emission of toxic gases into the environment. The process parameters, such as the effect of acid concentration, pulp density, temperature, time, etc., were studied, optimized, and scientifically validated. The kinetics of leaching fitted well with the following shrinking core models: XB = kc.t for Cu, (1 − (1 − XB)1/2) for Ni, and 1 − 3(1 − XB)2/3 + 2(1 − XB) for Pb. The activation energy was 19.42 kJ/mol. The tin left in the residue was treated separately. The developed process is useful for recovering metals from waste PCBs and has the potential to be commercialized after conducting scale-up studies.