Leaching-Extraction Process Of Low-Grade Zinc Oxide

With the depletion of easily processed zinc sulphide ore and high-grade zinc oxide coupled with the rapid development of the economy, low grade zinc has become an important material in the zinc smeltering and the economical utilization of low grade zinc has increasingly become an urgent issue. Low grade zinc ore is studied in this paper from the perspectives of thermodynamics and kinetics in the separation and enrichment of zinc and a direct leaching-extraction process was proposed. The basic contents and results were shown as follows:Agitation leach and heap leach were compared in this paper. It was shown in agitation leach experiments that the dosages of sulfuric acid and liquid-solid ratio are the main factors influencing zinc leaching yield. The yield increases with the increment of sulfuric acid and liquid-solid ratio. The acid addition method, agitation intensity, leaching time, particle size and reaction temperature also has influence on the zinc extraction. Under suitable conditions, the agitation leach yield could reach to 99.02%. The column leach results indicated that the leach yield could reach to 86.03% in nine weeks. Compared with agitation leach, heap leach is favorable in the leaching of low grade zinc ore with the advantages of low impurity yield and low acid consumption. Thermodynamics analysis of leach process suggests that acid leach of zinc oxide was exothermic reaction and equilibrium constant has great thermodynamics boost. Kinetics results show that leach process is controlled by diffusion process and categorized as restricted kernel module.D2EHPA was used as the extractant and 260 kerosene used as diluent in the extraction process. It is shown in zinc extraction condition experiments and cascade experiments that with 20% extractant concentration, phase ratio O/A 3:2, extraction intensity 200r/min, zinc extraction yield could reach to 38.19% in 10 minutes. The extraction yield could reach to 98.83% after five-stage countercurrent extraction under favorable conditions. Sulfuric acid could re-extract zinc from organic phase and render the separation of zinc and iron, thus provide suitable feed for the electro-winning process.