Influencing Factors Of Copper Dissolution In Sandstone-type Copper Deposits:Dissolution Experiment Of Malachite

The sandstone-type copper deposit is the second largest source of copper metal only next to the porphyry copper deposit,and the malachite is one of the main copper-bearing minerals in the copper oxide of the sandstone-type copper deposit,so the study of malachite can not be ignored.In this paper,by dissolving malachite in deionized water at different times,Na₂SO₄ solution at different concentrations,NaCl solution at different concentrations,and the temperature was changed under different conditions to measure the concentration of copper ions activated when malachite was dissolved at different temperatures for different times.By comparing the concentration of copper ions dissolved in deionized water/Na₂SO₄ solution of different concentration/NaCl solution at different temperatures,the concentration of copper ions activated by malachite at the same temperature,the same dissolution time and in different solvents,the results were compared.The results of this experiment show that:1.Malachite has low solubility in H₂O,and changing temperature has almost no effect on dissolution.2.Both Na₂SO₄ solution and NaCl solution have a significant effect on the dissolution of malachite,but the dissolution effect of malachite in NaCl solution is significant.In contrast,the solubility in Na₂SO₄ solution is limited,and the concentration of the two solutions is increased can further promote the dissolution of malachite,the above rule was also verified by the dissolution of the auxiliary experimental pure copper in deionized water and NaCl solution,respectively.The phenomenon that the concentration of copper ions activated in malachite at a temperature of 250?before and after the solvent is Na₂SO₄ solution may be due to the fact that the intermediate product formed during the dissolution reaction is easily oxidized,and the malachite competes for SO₄^2-,so the ability of malachite to dissolve copper ions is reduced.The abrupt change of copper ions concentration activated before and after the temperature of 300?in the solvent of NaCl solutionm ay be due to the formation and dissociation of Cu and Cl complexes.The experimental results are consistent with the previous conclusions proposed by the previous scholars that the brine temperature involved in the mineralization of sandstone-type copper deposits is about 250?,and that high salt?NaCl eq??8%⁴0%?and low temperature?<300??can form sandstone-type copper deposits.This conclusion also well explains that sandstone copper deposits are often associated with evaporite basins,salt springs,salt crusts,salt humps and gypsum formations,and even salt deposits associated with copper mineralization.That is to say,when brine with considerable concentration passes through sandstone-type copper deposits strata,some copper-bearing minerals in copper deposits will be dissolved in an appropriate amount,re-transported and accumulated for mineralization.