Abstract:
Recovery of metals from e-waste forms a major focus of circular economy thinking and aligns well with the Sustainable Development Goals (SDG). While hydrometallurgical extraction from electronic printed circuit boards (PCBs) is well established, the separation of metals from the leach liquors, which are complex mixtures, remains a challenge. To achieve selective separation, ion exchange resins with chelating functional groups were employed in the present study. Batch and column studies for selective recovery of Cu2+ from a given mixed metals leach solution were conducted using Dowex M4195 resin, and both the adsorption isotherm and kinetics were studied. The process involves three major steps: selective recovery of Cu2+ by M4195 at low pH and elution with H2SO4; sorption of Ni2+ from the raffinate by Dowex M4195 at pH 2 and removal of Fe3+ from raffinate. The batch experimental results showed appreciable and selective recovery of copper (51.1%) at pH 0.7 and 40.0% Ni2+ was sorbed from raffinate at pH 2.0 with co-adsorption of Fe3+ as impurity. The batch adsorption data could be fitted with both Langmuir and Freundlich isotherms and exhibited pseudo-second-order kinetics. Column studies agreed with the Yoon-Nelson model and indicated that Cu2+ break-through time in the column decreased with an increase in flowrate from 3.0 to 10.0 min/mL and decreased in sorption capacity, while it was delayed with increased bed heights from 20 to 30 mm. Complete elution of Ni2+ was obtained with 2.0 M H2SO4 after selective elution of trace impurities with dilute HCl. Iron in the raffinate was removed via the addition of Ca (OH)2 at pH 4.0 leaving Zn-Al in the solution.