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Mechanisms of Surface Passivation during Galena Leaching by Hydrogen Peroxide in Acetate and Citrate Solutions at 25–50 °C
ACS Sustainable Chemistry & Engineering ( IF 7.1 ) Pub Date : 2020-09-16 , DOI: 10.1021/acssuschemeng.0c04272 Fatemeh Nikkhou 1 , Fang Xia 1 , Manuel Knorsch 1 , Artur P. Deditius 1
ACS Sustainable Chemistry & Engineering ( IF 7.1 ) Pub Date : 2020-09-16 , DOI: 10.1021/acssuschemeng.0c04272 Fatemeh Nikkhou 1 , Fang Xia 1 , Manuel Knorsch 1 , Artur P. Deditius 1
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Organic solutions are promising lixiviants for fast and environmentally sustainable Pb extraction from ore minerals at low temperatures. However, engineering of novel leaching flowsheets has been hindered by poor understanding of the leaching mechanism, particularly the formation of surface-passivating phases. Here, we studied leaching of galena (PbS), the most abundant Pb ore mineral, in citrate and acetate solutions at 25–50 °C. The results show faster and higher Pb extraction in citrate solutions than in acetate solutions. For example, leaching of 53–106 μm galena particles at 35 °C for 2 h achieved 69.3% Pb extraction in a pH 7 citrate solution but only 30.1% in a pH 3 acetate solution. Investigation of solid residues by SEM, EDS, quantitative powder X-ray diffraction, and Raman spectroscopy proved the formation of a porous yet poorly permeable layer of anglesite during acetate leaching by pseudomorphic replacement of galena and subsequent overgrowth, hindering further leaching after 55.6% Pb extraction. In contrast, in citrate solutions, no anglesite was observed, but the formation of an impermeable thin Pb-oxide layer caused surface passivation after 87.1% Pb extraction. Our experimental results and thermodynamic calculations suggest that Pb-citrate complexes [e.g., Pb2(C6H5O7)22–, Pb(C6H5O7)24–, and Pb(C6H5O7)−] are far more effective than Pb-acetate complexes [e.g., Pb(CH3COO)+ and Pb(CH3COO)2] in suppressing the precipitation of anglesite because of the high solubility of Pb-citrate complexes in sulfate-rich solutions. This work provides a scientific basis for developing greener approaches such as in situ leaching and heap leaching for recovering Pb from galena-bearing ores.
中文翻译：
25–50°C的乙酸盐和柠檬酸盐溶液中过氧化氢浸出方铅矿的表面钝化机理
有机解决方案有望在低温下从矿石中快速，环境可持续地提取铅，成为有希望的毒药。但是，由于对浸出机理的了解不足，特别是表面钝化相的形成，阻碍了新型浸出流程的工程化。在这里，我们研究了在25–50°C的柠檬酸盐和乙酸盐溶液中方铅矿（PbS）（最丰富的Pb矿石矿物）的浸出。结果表明，与乙酸盐溶液相比，柠檬酸盐溶液中的Pb提取更快且更高。例如，在35°C下浸出53–106μm方铅矿颗粒2 h，在pH 7柠檬酸盐溶液中铅的提取率为69.3％，而在pH 3乙酸盐溶液中仅为30.1％。通过SEM，EDS，粉末X射线定量衍射对固体残留物进行研究 拉曼光谱法和拉曼光谱法证明，方铅矿的假晶置换和随后的过度生长会在醋酸盐浸出过程中形成角质位多孔但渗透性差的层，从而阻碍了55.6％Pb提取后的进一步浸出。相反，在柠檬酸盐溶液中，未观察到角位，但是在87.1％的Pb萃取后，不可渗透的Pb-氧化物薄层的形成导致表面钝化。我们的实验结果和热力学计算表明，柠檬酸铅复合物[例如，Pb 2（C 6 H 5 O 7）2 2–，Pb（C 6 H 5 O 7）2 4–和Pb（C 6 H 5 O 7）− ]比乙酸铅复合物有效得多。 [例如，Pb（CH 3 COO）+和Pb（CH 3 COO）2]，因为Pb-柠檬酸盐络合物在富含硫酸盐的溶液中具有高溶解度，因此可以抑制角位沉淀。这项工作为开发更绿色的方法提供了科学依据，例如原位浸出和堆浸以从方铅矿矿石中回收铅。
更新日期：2020-09-28
中文翻译：
25–50°C的乙酸盐和柠檬酸盐溶液中过氧化氢浸出方铅矿的表面钝化机理
有机解决方案有望在低温下从矿石中快速，环境可持续地提取铅，成为有希望的毒药。但是，由于对浸出机理的了解不足，特别是表面钝化相的形成，阻碍了新型浸出流程的工程化。在这里，我们研究了在25–50°C的柠檬酸盐和乙酸盐溶液中方铅矿（PbS）（最丰富的Pb矿石矿物）的浸出。结果表明，与乙酸盐溶液相比，柠檬酸盐溶液中的Pb提取更快且更高。例如，在35°C下浸出53–106μm方铅矿颗粒2 h，在pH 7柠檬酸盐溶液中铅的提取率为69.3％，而在pH 3乙酸盐溶液中仅为30.1％。通过SEM，EDS，粉末X射线定量衍射对固体残留物进行研究 拉曼光谱法和拉曼光谱法证明，方铅矿的假晶置换和随后的过度生长会在醋酸盐浸出过程中形成角质位多孔但渗透性差的层，从而阻碍了55.6％Pb提取后的进一步浸出。相反，在柠檬酸盐溶液中，未观察到角位，但是在87.1％的Pb萃取后，不可渗透的Pb-氧化物薄层的形成导致表面钝化。我们的实验结果和热力学计算表明，柠檬酸铅复合物[例如，Pb 2（C 6 H 5 O 7）2 2–，Pb（C 6 H 5 O 7）2 4–和Pb（C 6 H 5 O 7）− ]比乙酸铅复合物有效得多。 [例如，Pb（CH 3 COO）+和Pb（CH 3 COO）2]，因为Pb-柠檬酸盐络合物在富含硫酸盐的溶液中具有高溶解度，因此可以抑制角位沉淀。这项工作为开发更绿色的方法提供了科学依据，例如原位浸出和堆浸以从方铅矿矿石中回收铅。
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