Abstract:To address mineralogical characteristics of complex zinc-bearing minerals associated with multiple metals, complex phase composition, and high content of alkaline gangue, new technology of mineral complex coordination extraction with the first ligand of NH3 and the second ligand of ammonia triacetic acid (NTA) was proposed. Based on analysis of physical characteristics of complex zinc-bearing minerals, dissolution process of zinc component in single ligand model and composite ligand model was calculated, Ligands and complex coordination that can coordinate dissolve zinc silicate and stability constant of system were determined. Applying the principle of the lowest solubility of NTA under isoelectric point conditions, it is proposed to recover NTA from leaching solution by distilling ammonia and adding acid. The results show that the first ligand NH3 can only coordinate to extract carbonate-bearing zinc minerals, which limits the wide application of ammoniated coordination leaching to a certain extent. Stability constant of coordination of NH4Cl-NH3-NTA (0.5 mol/L) composite system is 14.08, which is 4.62 higher than that of NH4Cl-NH3 system. N atom of amino group in NTA and O atom in carboxyl group forms a stable metal chelate with zinc ions, which promoting traditional Zn(NH3)42+ complex conversion to more stable ZnNTA(NH3)2 multi-coordination complex, and zinc leaching rate rises by 113.4%. When pH value of leaching solution is adjusted to 1.30, NTA concentration in leaching solution drops to 1.15 g/L and NTA recovery rate is 96.0%. High-efficiency complex coordination extraction technology of complex zinc-bearing minerals has important guiding significance for breaking through efficient extraction and utilization of multi-mineral phase valuable metals under mild chemical environment.