METAL RECOVERY FROM E-WASTE BY CLAYS AND ACTIVATED CARBON

The growing global population and industrialization are driving an increasing demand for essential resources, particularly in key sectors such as the transition to climate neutrality and the development of innovative technologies. In this context, waste from electrical and electronic equipment (WEEE) represents a significant source of valuable materials. E-waste comprises various types of materials, including critical raw materials, plastics, and precious metals, each with different composition and recovery potential. The strategic raw materials are of particular interest, infact they play a vital role in the development of technologies for climate neutrality, aerospace, and safety sectors. These materials can be recovered and refined from e-waste, providing an alternative to environmentally damaging conventional mining practices. However, a large percentage of e-waste materials are currently discarded or lost, resulting in the waste of valuable metals and resources. To mitigate the environmental impact of traditional mining, several innovative techniques for material recovery are being explored, including pyrometallurgical, hydrometallurgical, and biotechnological methods. Among these, hydrometallurgy offers several promising technologies for metal separation, with solid-liquid adsorption standing out due to its high recovery efficiency, rapid extraction time, and the large quantities of adsorbents that can be utilized. This study investigates the adsorption of metal ions from a complex leachate solution derived from the leaching of milled mobile phone printed circuit boards (PCBs). The solution was analysed via ICP-OES (Inductively Coupled Plasma – Optical Emission Spectroscopy) to determine its composition. The multi-ions leachate was then exposed to two different sorbents, clay and activated carbon, both in their pristine and modified forms, while maintaining a fixed sorbent/solution ratio. ICP-OES analysis of the post-treatment solution allowed for the calculation of uptake efficiency for the different metals contained in the waste. The findings indicate the different behaviour of the sorbents towards the various ions. All the sorbents show the same uptake efficiency (of 100 wt.%) towards tin, while a different affinity is shown towards the uptake of copper: the clay reaches 1 wt.% of efficiency, while the other sorbents exceed 50 wt.%. Additionally, a release experiment was conducted under acidic conditions (pH = 1) to assess the release efficiency of each sorbent. Given that the leachate solution exhibited an extremely high concentration of copper (90 wt.%), a modified experimental setup was proposed, incorporating an electrodeposition step prior to adsorption. This new step significantly reduced the copper concentration from 21.5 g/L down to 1.58 g/L, reducing the amount of metal ions present in the solution.