Effect Of Toxic Organic Chemicals In Copper Solvent Extraction On A.Ferrooxidans

With the consumption of high-grade and manageable mineral resources, the resources crisis become more and more serious, reasonable full exploitation of mineral resources is significance. Hydrometallurgy operations have developed rapidly due to being environmentally friendly and low production costs, simple process handling etc.Biological leaching-solvent extraction-electrowinning operation is a typical technology of bioleaching copper. However the key limiting of the application of this technology is the leaching efficiency is too low. In fact, the circulation of the raffinate which loaded organic chemicals will definitely reach and pollute the bioleaching environment inhibiting the metabolism and bioleaching ability of the bacteria. In this paper, we study the effect of organic chemicals and the toxic component from copper solvent extraction on Acidithio-bacillus ferrooxidans in depth. It is great important to optimize bioleaching bacteria and improve bioleaching copper efficiency.With the increase of extractant concentration and extraction time, the metabolism of A.ferrooxidans and its bioleaching ability gradually decreased. The Fe2+-oxidation rate decreased by 75% in the presence of 15% extraction solvent. The strongest inhibition effect was shown after the first extraction cycle and 300rpm stirring extraction. Cells grown in culture solutions with solvent extraction chemicals exhibited differences in cell morphology and ultrastructure as compared to control cells. The cells were shortened and intracellular vacuoles increased.Being long-term touched with the acidic aqueous feed and strip reagent, Lix984N can be degraded gradually by such reaction mechanisms as Beckmann rearrange, hydrolyzing, oxidizing and sulfonating. With the increase of touched time between organic phase and acid, the bacteriostatic action of organic phase on A.ferrooxidans performance first reduce and then rise. The inhibition effect of organic phase touched acid 40-50 hours on A.ferrooxidans was minimum. This is due to that the antibiotic substances are degraded gradually after long term touch, so the inhibitions become reduce. Many kinds of amphiphiles containing such hydrophilic group as carbonyl, carboxyl, hydroxyl or acylamine are produced during the reagent degradations completely. The amphiphiles can destroy the cell membrane structure, so the inhibition of organic would strengthen.With the standing of raffinate, the entrained and dissolved organic phase will decrease because demulsification, volatilization and degradation. However the bacteriostasis of organic phase still can’t eliminate with the standing of raffinate.4-Nonylphenol which formed as modifier exists in LIX984N, studies have shown that with the increase of 4-Nonylphenol concentration, the metabolism of A.ferrooxidans and its bioleaching ability gradually decreased. The time of Fe2+oxidation completely delayed 48 hours in the presence of 4.3×10-5mol/L 4-NP, and the Cu bioleaching efficiency decrease by 10%. Cells grown in the culture solutions with 4-NP exhibited differences in cell ultrastructure as compared to control cells. The cell wall and plasma membrane become extremely blurred, The cell cytoplasm were highly clustered in the middle.The results suggest that the extraction process must consider its effect on bioleaching in practice. This may help to improve the whole bioleaching process.