Recycling or the treatment of e-waste is a global concern. There are several processes based on different technologies like pyrometallurgical, mechanical, and hydrometallurgical processes available for recycling. Each of these processes has disadvantages such as generation of flu gases, effluents, and being energy-intensive. There is a need to develop a safe, eco-friendly, and economically feasible process to recover metals from PCBs.

In this work, our first objective was to develop a hydrometallurgical process for treating PCB with nitric acid by recovering metals as metal salts sequentially. The focus is on tin, lead, and copper, which are present in significant quantities in PCBs. The process is scalable and is based on exploiting the physio-chemical interactions between the different metals and the acid. Tin and lead present in the solder are selectively dissolved at low acid concentrations (2-2.5 M). Further copper is recovered by dissolving in 4 M HNO3 or in ammoniacal solution.

For scaling up, our second objective was to do fundamental studies of metal dissolution kinetics to know various reactions involved and reaction time. For this, we did controlled experiments on copper dissolution in nitric acid. A kinetic model was developed and unknown parameters in the model were estimated by using particle swarm optimization technique. This kinetic modeling will help us in designing reactors and absorption column (NOx absorption).

Further to make the process economically viable, our third objective was on recovering copper as stable copper nanoparticles. These nanoparticles were synthesized in both batch and continuous mode without any inert atmosphere and were found to be stable for at least 8 months.

Further, for synthesizing monodispersed nanoparticles, the focus was to incorporate multiphase flow (Segmented flow) where each slug acts like a microreactor. In literature, Oil-water immiscible system was used for generating segmented flow. Due to the presence of the organic phase, the applications of nanoparticles become limited. Our fourth objective was to use Aqueous Two-Phase System (ATPS) for generating segmented flow in millichannels. Hydrodynamics of ATPS in millichannel were studied in detail and then nanoparticle synthesis was performed in segmented flow.