The Leaching of Dolomitic-Copper Ore Using Sulphuric Acid Under Controlled Conditions~!2010-03-15~!2010-06-17~!2010-07-21~!

Abstract

The leaching of dolomitic-copper ore using sulphuric acid under controlled conditions was studied with a view to evaluating the economic value and the effect of ore pulverisation, particle size, temperature and pH on the recovery of copper from chalcopyrite. The samples were ground and mixed with water and sulphuric acid to form an acid soluble copper content of 4.07 %, 8.14 % total copper and 22 % solids. The leaching was carried in duration of 0-6 hours. The sulphuric acid was found to be effective in recovering copper from chalcopyrite with efficiencies of 72 to 93 % for 75 micron particle size and 65 to 84% for the 212 micron sieve size at different pulverising times. The kinetics of dolomitic ore showed the reaction with H2SO4 was second order with respect to chalcopyrite and first order with respect to dolomite and was consistent with the shrinking core model. The increase in temperature produced an increase in the recovery of copper from solids into the bulk solution. The leaching was favoured at low pH values (1.8 3). Profit levels for the reversed pH numbers, high to low (low to high pH), were higher than values for leaching from low to high pH numbers (high to low pH) particularly for acid sales. Since the economic evaluation showed positive profit levels for both acid and copper sales, the process was viable. Leaching can be controlled by a number of factors in order to optimize the usage of materials. The concentration of acid, particle distribution, temperature, pulverisation and leaching duration are some of the factors that can be used. The concentration of the acid determines the pH of the slurry to be leached. Increased level of acid can allow unwanted metals to dissolve and may be leached along with the desired metal. The particle distribution has the advantage of easy separation of the desired mineral from gangue, easy expo- sure of the mineral to chemical reaction and producing the desired surface area. A finer particle distribution produces a higher leach extraction (3). The concentration of solids can affect leaching in two ways. High concentration can increase viscosity and cause blockage problems and reduce copper extraction rate due to lack of fluidity (4). Low concentration can increase the overall slurry overflow rate and this can