Leaching Kinetics of Willemite in Ammonia-Ammonium Chloride Solution

• Published in: Metallurgical and materials transactions. B, Process metallurgy and materials processing science Process metallurgy and materials processing science, 2011-08, Vol.42 (4), p.633-641
• Main Authors: Ding, Zhiying, Yin, Zhoulan, Wu, Xifei, Hu, Huiping, Chen, Qiyuan
• Format: Article
• Language: English
• Subjects: Ammonia; Applied sciences; Characterization and Evaluation of Materials; Chemical reactions; Chemistry and Materials Science; Chlorides; Diffusion; Diffusion rate; Exact sciences and technology; Leaching; Materials Science; Mathematical models; Metallic Materials; Metals. Metallurgy; Nanotechnology; Particle size; Production of metals; Reaction kinetics; Solvent extraction processes; Structural Materials; Surfaces and Interfaces; Thin Films; Zinc
• ISSN: 1073-5615; 1543-1916
• DOI: 10.1007/s11663-010-9472-3

The leaching kinetics of willemite in ammonia-ammonium chloride solution was investigated. The effects of the ammonia-ammonium ratio, particle size, temperature, and total ammonia concentration on the leaching rate of willemite were determined. The results show that the optimum ammonia-ammonium ratio is 1:2 over the studied range. The zinc extraction increases with the reduction of particle size and with the increase of temperature and the total ammonia concentration. Leaching kinetics indicate that the grain pore model could be adopted to describe the leaching process, and diffusion is the main rate-controlling step. The apparent activation energy was determined to be 54.47 ± 6.39 kJ/mol and a reaction order with respect to NH 3 (aq) was 3.16 ± 0.40, both of which are likely a result of the parallel nature of the chemical reaction and diffusion in porous solids, even if the chemical reaction is not the rate-controlling step.