An efficient approach for simultaneous CO2 mineralization and nickel separation from laterite leachate

Abstract

Currently, nickel production is mainly based on a high−carbon−footprint refining process. An alternative low−carbon nickel recovery method is vital for sustainable development. This study presented a technique for nickel separation and CO₂ mineral sequestration from a nickel and magnesium−containing leachate. Eh − pH results showed that the conditions for forming nickel−ammonium complexes closely aligned with those for magnesium carbonate formation. Thus, magnesium was selectively separated by injecting CO₂ and ammonia. Under the conditions of Mg²⁺ concentration of 0.8 mol/L, NH₃/Mg molar ratio of 8, CO₂ flow rate of 200 ml/min, injection time of 60 min, and aging time of 60 min, magnesium precipitation ratio approached 100 %, with nickel loss below 1 %. Increased concentrations of [NH₃] and [CO₂] in the solution facilitated the separation of magnesium and nickel, while promoting the precipitation of magnesium ions as porous MgCO₃·3H₂O clusters. Nickel can be recovered as NiCO₃ from the Mg − depleted solution by evaporation. This paper integrated CO₂ mineralization with the recovery of valuable nickel into a single step, maximizing nickel selectivity and minimizing CO₂ emissions.