Abstract:

The COMAN process introduces a selective hydrometallurgical route for recovering copper, cobalt and manganese from mining tailings and secondary resources. The process flowsheet combines beneficiation (including comminution, classification, gravity, and flotation) with sustainable bioleaching, followed by a purification stage designed for high selectivity and product purity.

This work describes the solution purification and metals recovery stages of the COMAN process. Bioleachates from sulphidic resources typically contain Fe(III) at concentrations that complicate recovery of Cu and other critical metals. The widely used hydroxide precipitation of Fe(III) (with CaCO₃ as a reagent) often leads to coprecipitation losses of Cu and Co and excessive generation of gypsum waste. To mitigate coprecipitation of target metals and decrease waste generation, the COMAN process removes iron as a phosphate phase (FePO₄). The iron removal is followed by selective sulphide precipitation using H₂S gas to recover Cu, Zn, Co, and Mn. The sulphide route provides highly selective separation and favourable filtration characteristics while limiting the addition of foreign cations, although complete avoidance is not possible. Where pH control is required, ammonium-based reagents are preferred so that added NH₄⁺ can be recovered and recycled.

The study integrates batch experiments to identify the optimal operating parameters (pH, redox, and reagent consumption) with continuous validation to demonstrate process stability and scalability. The COMAN flowsheet offers a practical approach for hydrometallurgical treatment of bioleachates—reducing reagent consumption and improving impurity management while simultaneously minimising waste.

This work is supported by the European Union’s Framework Programme for Research and Innovation 'Horizon Europe', with the METALLICO project [Grant number 101091682]

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Mr. Pirkka Ollonqvist