Given the increasing use of seawater containing primary ions (e.g. Na and Cl) and secondary ions (e.g. Ca and Mg) in flotation plants to counteract the global freshwater scarcity, more and more studies have been performed to determine the impacts of seawater on mineral flotation behaviors. From a new and practical niche, this study aimed to determine the natural floatability of chalcopyrite in the presence of Ca as a secondary ion by considering the alterations of surface hydrophobicity from both the aspects of surface oxidation and metal ion precipitation. Through true collectorless flotation, Cyclic Voltammetry analyses, calcium speciation and Cryogenic X-ray Photoelectron Spectroscopy measurements, this study identified that the true flotation recovery of chalcopyrite was much lower in CaCl solutions than in NaCl solutions even with the same ionic strengths. While the presence of NaCl enhanced chalcopyrite surface oxidation to produce hydrophobic and hydrophilic products, the presence of CaCl inhibited chalcopyrite surface oxidation through the formation of CaCO precipitate which not only served as a passive layer but also being hydrophilic itself. As a result, the surface hydrophobicity on chalcopyrite was determined by the amount of oxidation products in NaCl solutions, but it was determined by the amount of CaCO precipitate in CaCl solutions. Despite the larger amount of CaCO precipitate in CaCl solutions with ionic strengths of 0.7 and 1.2 M, compared to deionized water and CaCl solution with an ionic strength of 0.1, the true flotation recovery of chalcopyrite was higher. This was attributed to much smaller air bubbles generated in CaCl solutions with high ionic strengths of 0.7 and 1.2 M, promoting bubble-particle collision and hence the true flotation of chalcopyrite.

中文翻译：

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识别氯化钙溶液中黄铜矿的真正无捕收剂浮选

鉴于浮选厂越来越多地使用含有一次离子（例如Na和Cl）和二次离子（例如Ca和Mg）的海水来应对全球淡水短缺问题，越来越多的研究已经进行，以确定海水对矿物浮选的影响行为。本研究从一个新的实用领域出发，旨在通过从表面氧化和金属离子沉淀两个方面考虑表面疏水性的变化，确定在 Ca 作为二次离子存在下黄铜矿的自然可浮性。通过真正的无捕收剂浮选、循环伏安分析、钙形态和低温 X 射线光电子能谱测量，本研究发现，即使离子强度相同，氯化钙溶液中黄铜矿的真正浮选回收率也比氯化钠溶液中低得多。虽然 NaCl 的存在增强了黄铜矿表面氧化，产生疏水性和亲水性产物，但 CaCl 的存在通过形成 CaCO3 沉淀来抑制黄铜矿表面氧化，CaCO3 沉淀不仅充当钝化层，而且本身也具有亲水性。因此，黄铜矿的表面疏水性由 NaCl 溶液中氧化产物的量决定，而由 CaCl 溶液中 CaCO 沉淀的量决定。尽管离子强度为0.7和1.2 M的CaCl溶液中CaCO沉淀量较多，但与去离子水和离子强度为0.1的CaCl溶液相比，黄铜矿的真实浮选回收率较高。这是由于在具有 0.7 和 1.2 M 高离子强度的 CaCl 溶液中产生的气泡要小得多，促进了气泡与颗粒的碰撞，从而促进了黄铜矿的真正浮选。