Selective isolation of heavy metals from spent electronic waste solution by macroporous ion-exchange resins

Highlights: • The heavy metals present in an e-waste solution were individually isolated with high precision. • Selective isolation can be applied on any complex solution containing heavy metals. • The optimal adsorption mechanism for each ion was introduced after model fitting. • The preferred location of each adsorbed ion was investigated via SEM and EDS mapping. -- Abstract: Electronic waste (e-waste) has become an urgent issue in digitally dependent world, owing to the unprecedented use of electronic devices and this has compelled the world to develop new techniques to recycle such wastes. In this work, one of problematic and high volume global waste stream, i.e., end-of-life printed circuit boards (PCBs), was examined for recycling. Using ion-exchange (adsorption/desorption) technique, heavy metals (Cu, Zn, Ni, and Pb), and Al were selectively recovered and separated. Three macroporous ion-exchange resins (Amberlite IRA 743, Lewatit TP 208, and Lewatit TP 260) were applied to extract, isolate and concentrate the heavy metals. The process factors (resin load, solution temperature and contact time) were investigated and kinetic behavior of adsorption was studied using three different models. Based on the process factors, the functionality and selectivity of the ion-exchange resins were discussed. A negligible amount of Ni and Zn adsorption on the surface of resin 743 indicates its high selectivity. This study also proves that selective isolation of hazardous elements such as Pb can be performed under specified sorption parameters. Also, the distribution of adsorbed cations throughout the resin beads was studied via elemental analysis. The distribution of Cu as the main element was not homogenous that signifies the higher practical capacity of the ion-exchanger. Finally, a stripping step was applied to modify the working media and to examine the reversibility and selectivity of the desorption process.