LEACHING Zn FROM THE LOW-GRADE ZINC OXIDE ORE IN NH3-H3C6H5O7-H2O MEDIA

Abstract

-In this research, the effect of different citric acid concentrations, ammonia concentration, temperature, leaching time, stirring speed and liquid-to-solid ratio on the zinc leaching from low-grade zinc oxide ore in a NH 3 -H 3 C 6 H 5 O 7 -H 2 O system were studied. The results showed that the zinc leaching rate is only 4.7% when the citric acid concentration is 0 M, and the leaching efficiency of Zn increased with increasing citric acid concentration. Under the conditions: citric acid concentration of 1.0 M, ammonia concentration of 6 M, temperature of 25 °C, leaching time of 60 min, stirring speed of 300 rpm and the starting solid-to-liquid ratio of 1:5, 81.2% of Zn is leached. The mineralogical changes of the low-grade zinc oxide ores during the processes were characterized by X-ray fluorescence (XRF), X-ray powder diffraction (XRD), Scanning Electron Microscopy associated with Energy Dispersive Spectroscopy (SEM-EDS) and Fourier transform infrared spectroscopy (FT-IR). From the evidence we deduced that citric ions complexed with zinc ions, forming a Zn-citrate complex. As a result, the zinc leaching rate was improved without the risk of pollution or pretreatment. This makes it as a good choice for a more ecological treatment of hemimorphite.

Studies on zinc recovery from technogenic waste

“…%) and manganese (1.5 -5.6 wt. %) as main other metals [10,11]. Citric acid [12] and ammonia-citric-acid-water [13] systems were also studied.…”

Removal of Heavy Metals (Lead, Cadmium and Iron) from Low-Grade Nanoscale Zinc Oxide Using Ammonium Carbonate Solution as a Leaching Agent

“…The leach-solvent p-extraction process route is a latest economical method used for the removal of heavy metal impurities from commercial low-grade ZnO [4]. Low grade ZnO can also be treated with conventional acidic heap leaching process [5] but ammonia and alkaline leaching is the selective system for purification of ZnO because of significant operating cost and environmental concern [6].…”