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4371048 
Journal Article 
Recovery of zinc and the regeneration of the complexation agent from the NH4Cl-NH3-NTA system 
Rao, S; Zhang, D; Yang, T; Ling, H; Liu, W; Chen, Lin 
2017 
Yes 
Hydrometallurgy
ISSN: 0304-386X 
ELSEVIER SCIENCE BV 
AMSTERDAM 
169 
508-514 
WOS:000401878200060 
In this work, the leaching behavior of the major components, i.e., Zn, Pb and Fe, of refractory hemimorphite in an ammonium chloride-ammonia-nitrilotriacetic acid (NH4Cl-NH3-NTA) system was investigated in detail. The thermodynamic analysis of the Zn2+-NTA(3-)-Cl--NH3-H2O and Pb2+-NTA(3-)-Cl--NH3-H2O systems demonstrated that the predominant zinc and lead species in the leaching solution were the ZnNTA(NH3)(2)(-) and PbNTA(-) complexes, respectively. The results of the leaching experiments indicated that more than 85% of Zn, 60% of Pb and less than 3% of Fe were leached from refractory hemimorphite using 2 mol/L NH3-2 mol/L NH4Cl-0.15 mol/L NTA as the leaching agent at 40 degrees C with a liquid-solid ratio of 10 mL/g. Moreover, a feasible method for zinc recovery and ligand regeneration was proposed: the ZnNTA(NH3)(2)(-) complex leaching solution was transformed into a zinc chloride solution through ammonia distillation and an acidity adjustment process. More than 96.0% of the NTA was recovered when the leaching solution pH was reduced to 1.0. (C) 2017 Elsevier B.V. All rights reserved. 
Leaching; Complexes; Recovery; Regeneration