Optimisation of the dissolution and crystallisation process for the recovery of nickel sulphate from industrial sludges

The European Union’s shift toward renewable energy has placed critical raw materials at the core of its industrial policy agenda, with nickel identified as a crucial component for battery technologies. As a result, the recovery of nickel from secondary sources, such as industrial wastewater, has become increasingly important to support the circular economy and reduce the EU’s dependence on primary raw materials and external suppliers. This Thesis investigates a laboratory-scale wet-chemistry process for recovering nickel in the form of sulphate from galvanic wastewater treated with supercritical water, a novel metal-recovery technology developed within the RECOVER-IT project by Circular Materials s.r.l. (Padova, Italy). In particular, the experimental work focuses on the acid dissolution and subsequent crystallisation of galvanic sludges obtained from the supercritical water treatment, aiming to explore the feasibility of producing nickel sulphate at technical- or commercial-grade purity. The findings are intended to establish a reproducible, easy-to-implement experimental basis for future scale-up operations, contributing to ongoing efforts towards a sustainable recovery pathway for critical and strategic raw materials.