Effect of heating on structure and leaching characteristics of a zinc carbonate ore


Kumas C., OBUT A.

PHYSICOCHEMICAL PROBLEMS OF MINERAL PROCESSING, vol.57, no.5, pp.23-32, 2021 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 57 Issue: 5
  • Publication Date: 2021
  • Doi Number: 10.37190/ppmp/140096
  • Title of Journal : PHYSICOCHEMICAL PROBLEMS OF MINERAL PROCESSING
  • Page Numbers: pp.23-32
  • Keywords: calcium zincate, smithsonite, sodium hydroxide leaching, zinc carbonate ore, zinc oxide, FLOWER-LIKE ZNO, ALKALINE, HYDROXIDE, PRECIPITATION, KINETICS, CRYSTALLITES, FABRICATION, PARTICLES, BEHAVIOR, GROWTH

Abstract

In this work, the structural changes occurred in a zinc carbonate (smithsonite) ore sample following heating at temperatures between 523 K and 1173 K were investigated in detail using X-ray diffraction (XRD), thermal (TG/DTA) and Fourier-transform infrared (FT-IR) spectroscopy analyses. Afterwards, the leaching characteristics of zinc from the ore sample and the heated ore samples in sodium hydroxide solutions were determined. While heating at 523 K did not cause any structural change in the ore sample, heating at 723 K completely converted smithsonite (ZnCO3) in the ore sample to zinc oxide (ZnO), which resulted lower zinc leaching efficiencies of 40.6% and 62.0% for 3 and 4 mol/dm3 NaOH concentrations, respectively, in comparison to zinc leaching efficiencies (67.2% and 70.7%) obtained for the unheated ore sample. On the other hand, due to neoformation of dissolution resistant ZnFe2O4, Ca2ZnSi2O7 and Zn2SiO4 phases during heating and formation of CaZn2(OH)(6)center dot 2H(2)O phase during leaching, the leaching efficiency of zinc further decreased to 22.2% and 31.3%, respectively, in 3 and 4 mol/dm(3) NaOH solutions for the ore sample heated at 1173 K. The formation of zinc-containing dissolution resistant phases by high-temperature heating was observed to be the only reason for the reduction in the zinc leaching efficiency (49.4% at 1173 K) at the highest NaOH concentration (8 mol/dm(3)) studied. In this work, the comparative precipitation studies were also conducted and crystalline zinc oxides with different morphologies could be precipitated at considerably high efficiencies from the selected pregnant solutions obtained following leaching.