云南元江高镁红土矿矿物组成及浸出热力学分析

采用显微镜观察、X射线衍射分析和扫描电镜能谱分析等手段研究元江镍矿的矿物组成,并对矿石中有价金属的浸出反应进行热力学分析。结果表明,元江镍矿是蛇纹岩风化形成的硅酸镍矿,主要矿物组成为含镍蛇纹石、针铁矿、石英、磁铁矿以及少量的辉石、滑石和赤铁矿等,各矿物间关系密切。元江镍矿的浸出过程比较复杂,矿石中主要矿物的浸出反应很容易进行,并且有价金属浸出比较完全。

Kinetic study of high-pressure acid leaching of Mg and Ni from serpentine

Inner Mongolian serpentine ore was subjected to sulfuric acid leaching tests,and the effects of the leaching process parameters on the leaching efficiency of different metals were investigated.The leaching efficiency of Mg,Fe,Al,Ni,and Co reaches 93.98%,60.09%,82.08%,90.58%,and 94.06%,respectively,under the leaching conditions of 5 mol/L H_(2)SO_(4),liquid/solid ratio of 4 mL/g,and leaching temperature 100℃.Hence,the valuable metals in serpentine were effectively recovered by sulfuric acid leaching.The leaching behaviors of Mg,Fe,and a small amount of Al were analyzed using X-ray diffraction.The results show that the unreacted Mg and Fe remained as MgFe_(2)O_(4),and Al formed Al_(2)Si_(2)O_(5)(OH)_(4) in the leaching residue.The kinetics of Mg and Ni in the leaching process was studied respectively.The leaching kinetics of Mg conformed to the shrinking core model with an activation energy of 16.95 kJ/mol,which was controlled by the combination of the diffusion and chemical reaction.The leaching kinetics of Ni accorded with the Avrami equation with an activation energy of 11.57 kJ/mol,which was controlled by diffusion.In the study,the valuable metal elements were extracted from serpentine minerals with high efficiency and low cost,which possessed important practical values.

Enhancement of CaMoO_(4) calcine decomposition and recovery of calcium resource by HCl cycle leaching

The thermodynamic equilibrium diagrams of CaMoO_(4)-CaSO_(4)-H_(2)SO_(4)-H_(2)O,CaMoO_(4)-HCl-H_(2)O and CaSO_(4)-CaCl_(2)-HCl-H_(2)O systems at 298 K were established.The calculation results demonstrated that HCl displays a much higher solubility of CaSO_(4)than H_(2)SO_(4).The leaching mechanism of Mo from CaMoO_(4)calcine was systematically investigated from the perspective of the micro particle properties variation.HCl exhibits an excellent leaching performance for Mo from CaMoO_(4)calcine due to the elimination of surface coating and the dissolution of a mass of Mo embedded in CaSO_(4)matrix.Excellent Mo leaching efficiency of 99.7%was achieved under the optimal conditions of decomposing CaMoO_(4)calcine by 2.4 mol/L HCl with a liquid/solid ratio of 10:1 at 50°C for 60 min.Based on the experimental results,a highly efficient and green cycle leaching process of molybdenum from molybdenite was proposed,which eliminated surface coating and physical entraining,and converted most of the calcium from CaMoO_(4)calcine into high purity gypsum by-product.

pH-dependent leaching mechanism of carbonatitic chalcopyrite in ferric sulfate solution

The dissolution of a carbonatitic chalcopyrite(CuFeS2)was studied in H_(2)SO_(4)−Fe_(2)(SO_(4))_(3)−FeSO_(4)−H_(2)O at varying pH values(0.5−2.5)and 25℃ for 12 h.Experiments were conducted with a size fraction of 53−75μm.Low Cu recoveries,below 15%,were observed in all pH regimes.The results from the XRD,SEM−EDS,and optical microscopic(OM)analyses of the residues indicated that the dissolution proceeded through the formation of transient phases.Cu_(3.39)Fe_(0.61)S_(4) and Cu_(2)S were the intermediate phases at pH 0.5 and 1.0,respectively,whereas Cu_(5)FeS_(4) was the major mineral at pH 1.5 and 1.8.The thermodynamic modelling predicted the sequential formation of CuFeS_(2)→Cu_(5)FeS_(4)→Cu_(2)S→CuS.The soluble intermediates were Cu_(5)FeS_(4) and Cu2S,whilst,CuS and Cu_(3.39)Fe_(0.61)S_(4) were the refractory phases,supporting their cumulating behaviour throughout the dissolution.The obtained results suggest that the formation of CuS and Cu_(3.39)Fe_(0.61)S_(4) could contribute to the passive film formed during CuFeS_(2) leaching.

Leaching process of selenium residue

A thermodynamics analysis on the leaching process of selenium residue and discussion on the behaviors of aqueous ionic in the leaching process were carried out. Through thermodynamical calculation, the values of AG and relevant potential expressions were obtained. According to these thermodynamical data, the φ-pH diagrams of Se-H2O system at 298 and 373 K were obtained; Simultaneously, the φ-pH diagrams of SO2-H2O and SO2-Se-H2O systems were drawn at 298 K. With increasing the temperature, the stable regions of HSeO3, SeO2- and SeO2- in the φ-pH diagram of Se-H2O system become gradually large, but the limits of pH in the stable region become gradually small. The stability area of reduction precipitation in the SO2-Se-H2O system was finally determined. The results of oxidization leaching experiments of selenium residue indicate that when the mass ratio of selenium residue to sodium chlorate is 2, the concentration of sulfuric acid is 300 g/L and the residue is agitated for 3 h at leaching temperature of 80 ℃, the leaching rate of selenium could reach 97.76 %. The experimental results conform the calculated results by φ-pH diagram. The selenium reduction precipitation in oxidization-leaching solution was analyzed under the conditions of acidity of 150 g/L, the sodium sulphite concentration of 35 g/L at the reductive temperature of 23 ℃ for 120 min. And this demonstrates the thermodynamics analysis.