Work package 3 (WP3) – Hydrometallurgical treatment of ultrafine IBA particles

Incineration bottom ash is a heterogeneous material composed of numerous mineral phases. This gravel-like material contains both fine and very fine particles together with bigger fragments of glass and ceramics. Organic fraction is also present. Together with these major components, numerous elements are presents in trace quantities. Metals like copper, zinc, nickel, chromium, rare earths, PGMs can be found in concentration up to several thousands of ppm.

Within ReFina project the feasibility of trace metals recovery by hydrometallurgy approach, based on their successive leaching, separation and recovery, is currently developed. The first process step, called leaching, is based on the dissolution of metallic elements and is traditionally carried out using very diverse leaching agents with the objective to obtain the metals under an ionic form within a solution (either as ionic species – cations or anions or neutral complexes). Amongst them inorganic or organic acids, bases, complexing agents, oxidizers … can be cited. The chosen leaching agent should be cheap, available at big quantities, the least toxic possible, efficient and if possible selective. As all these criteria are rarely met all, several metals could be found then in the solution and several separation steps (such as solvent extraction, ion exchange …) might be necessary prior to final recovery by precipitation or electro-deposition under a solid form.

The choice of the leaching agent and the subsequent separation techniques is fully dependent on the composition of the solid matrix and the cost and time requirements. The number of elements to recover and their requested purity are also important parameters to be considered. Within the Refina project copper and zinc have been chosen is elements of interest and their recovery from the received matrix is currently developed. The leaching step is carried out under column configuration to mimic heap leaching conditions and the selective recovery from of both elements from the leachate is being optimized.