Effect Of Copper Solvent Extraction Reagents On Interfacial Interactions During Bioleaching Progress

In biohydrometallurgy process for copper extraction from sulfide ores,a small amounts of organic phase will remain in the recyclable raffinate of solvent extraction(SE)operation through dissolving and entraining as emulsion droplets.These losed organic chemicals will pollut the bioleaching site,impact the leaching bacteria and finally impede the bioleaching process.The effects of SE organic chemicals containing ketoximes and oxime extractants on the metabolism,adsorption behavior,extracellular polymer(EPS)secretion and biofilm construction of Acidithiobacillus ferrooxidans(A.ferrooxidans)and Acidithiobacillus thiooxidans(A.thiooxidans)were investigated,respectively.The results showed that the SE organic chemicals inhibited the metabolism of A.ferrooxidans and A.thiooxidans.Also,they impacted the bioleaching of chalcopyrite concentrate by A.ferrooxidans,reduced the bioleaching activity.The LIX84-ICNS inhibited the growth of this two kinds of bacteria more than LIX860N-I.Under the influence of 10% v/v LIX860N-I SE organic phase,the cells of A.ferrooxidans delayed 15 days to start the exponential growth.The rate and ratio of adsorption for the cells of A.ferrooxidans and A.thiooxidans on the surface of the sulfide ores increased in the presence of SE organic chemicals.The effect of LIX860N-I on the adsorption behaviors of two kinds of cells is more obvious than that of LIX84-ICNS.The adsorption rate and ratio of cells of A.ferrooxidans rose more obviously than that of A.thiooxidans.When the bioleaching environment was pulluted by the SE organic phase containing 15% v/v of LIX860N-I,the equilibrium adsorption rate o f the cells of A.thiooxidans and A.ferrooxidans increased by 10% and 20%,respectively.Althought the SE organic chemicals increased the adsorption rate and ratio of bacterial cells,they did not promote the growth and leaching efficiency of bacteria.Meanwhile,more natrojarosite may precipitated under the influence of the SE organic chemicals,which hindered the bioleaching process.A.ferrooxidans bacteria attached the surface of pyrite ore no-polluted by SE organic phase mainly in the way of evenly dispersed single cell.When the surface of pyrite ore was contaminated by the SE organic phase,the number of A.ferrooxidans cells adsorbed in a unit area increased,and the way of single cell adsorption is rare,displased by the aggregating adsorption.Under the influence of LIX84-ICNS,the cells are densely packed around a circumference,and a small number of chains are observed.Under the influence of LIX860N-I,more A.ferrooxidans cells adsorbed mainly in chains and the cell chains interlinked to each other.The attached cells dispersed more uniformly than under the influence of LIX84-ICNS.The attachment pattern of the cells is similar to the appearance of the organic droplets on the surface of the ore,indicated that lipophilic mechanism is an important reason for the SE organic phase to promote the cell attachment.In the unpolluted environment,the secretion of EPS for the cells of A.thiooxidans and A.ferrooxidans were exuberant,and the irregular biofilm covered the cell community was found on the ore surface.Under the effect of SE organic chemicals,the EPS on the cells' surface decreased.Under the influence of LIX84-ICNS,a few cells were encapsulated by translucent substances,and some bacteria were uncovered.Under the influence of LIX860N-I,no biofilm was found,and almost all of the cells were uncovered.Under the impacts of copper SE organic chemicals,the secretion of macromolecules protein and polysaccharides in EPS for A.ferrooxidans and A.thiooxidans decreased on the whole(except that the secretion of protein in EPS for A.thiooxidans bacteria increased when polluted by 10%LIX860N-I organic phase).The secretion of each component in EPS for A.ferrooxidans and A.thiooxidans decreased more under the influence of LIX860N-I than under LIX84-ICNS.The antagonism of A.thiooxidans cells to copper SE organic chemicals to membrane damage was worse than A.ferrooxidans cells.Different copper extractant had different effects on the attachment behavior,metabolic activity,EPS secretion and biofilm formation of different bacteria.