A Green and Efficient Process for the Stepwise Extraction of Cu, Ni, Co, Zn, and Mn from Nickel Laterites Based on the Novel Solvent Extraction System of DNNSA-NNPA

Developing a novel extraction process for battery minerals-nickel laterites is a key aspect of building a resilient and low-carbon future, as the current process produces heavy metal residues, electrolytic wastewater, and toxic gases, while also facing issues of long process flow and low resource utilization. The primary bottlenecks in the process stem from the low separation coefficients and poor selectivity of commercial extractants. In this paper, a novel synergistic solvent extraction (SSX) system, dinonylnaphthalenesulfonic acid (DNNSA)-N,N-bis(pyridin-2-ylmethyl)tetradecan-1-amine (NNPA), has been proposed to address the bottlenecks. Based on the DNNSA-NNPA SSX system, a novel hydrometallurgical process has been proposed for the stepwise extraction of valuable metals from nickel laterites. In the proposed process, Cu, Ni, Co, and Zn were directly extracted from the nickel laterite leachate, reducing their concentrations to below 1 mg/L. The enriched metals were subsequently separated as CuSO4, NiSO4, CoSO4, and ZnSO4 solutions, each with a purity exceeding 99.9%. Thereafter, Cr, Fe(III), and Al were sequentially removed from the raffinate through stepwise precipitation, achieving their preliminary separation. Mn was then selectively extracted from the resulting precipitate–mother liquor, yielding a high-purity MnSO4 solution (>99.9%). This integrated approach enables the comprehensive resource extraction of nickel laterites. Systematic mechanistic studies and pilot plant tests demonstrate that the novel extraction process significantly improves metal ion separation coefficients, avoids coprecipitation losses of Ni and Co, simplifies the process flow, avoids hazardous waste generation, reduces energy consumption, and improves resource utilization.