COLUMN BIOLEACHING OF A LOW-GRADE NICKEL-BEARING SULFIDE ORE

摘要

Yellow Mountain Deposit belonging to GobiMin Inc is located in the Chinese Tianshan and Altayrnorogenic belts, Hami, Xinjiang Province, NW China. Indicated Mineral Resources of its reservernare estimated at 12 million tonnes averaging 0.40 per cent nickel. Mineralogical examination andrnchemical analysis indicated that the Yellow Mountain ore is a type of high Fe, low Mg and low Nirnsulfide ore: the main sulfide minerals are ～8.0 per cent pyrrhotite (Fe_(1-x)S), ～1.0 per cent pentlanditern((Fe, Ni)_9S_8), ～0.6 per cent chalcopyrite (CuFeS_2), ～0.5 per cent pyrite (FeS_2), and ～0.2 per centrnviolarite((Fe, Ni)_3S_4); the main gangue minerals are ～48 per cent olivine, ～28 per cent antigorite,rn～3 per cent chlorite, ～2 per cent talc, ～2 per cent tremolite, and～1.5 per cent magnetite; the chemicalrnanalysis of the ore sample are Ni 0.40 per cent, Co 0.016 per cent, Cu 0.24 per cent, Fe 12.4 perrncent, S 5.6 per cent, MgO 9.6 per cent, CaO 1.80 per cent, SiO2 48.5 per cent and Al_2O_3 10.3 perrncent. Preliminary results of the shake flask test showed that pyrrhotite is easily leached and thernhigh concentration of ferric iron would hamper the growth of bacteria which will bring a negativernimpact on the bioleaching conversely. This work aims to set up a method to prevent the negativernimpact of the ferric ion on the bioleaching of the ore. Two method were combined to prevent thernnegative impact of the ferric ion, they are adaptation of the mixed bacteria to iron ion and bleedingrnthe off-solution periodically to control the levels of iron ion (depending on the tolerance of thernmicroorganisms to the ferric ion) in the leaching solution. Using a mixed mesophiles composed ofrnAcidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans underrnroom temperature, a nickel recovery of 93 per cent and a cobalt recovery of 85 per cent were achievedrnin 280 days column bioleaching process with an average nickel concentration in the leaching solutionrnof 2.6 g/L. The results showed that the negative effect of the ferric ion can be successfully controlledrnand the nickel can be bioleached successfully from theYellow Mountain ore.