In the flotation of water-soluble minerals (e.g., NaCl and KCl crystals), the high ionic-strength environments alter the typical interfacial interactions and challenge the applicability of conventional flotation theories. Here, we report an intriguing effect of Pb(II) ions on the flotation of NaCl and KCl crystals in brines using sodium/potassium laurate as collectors. We revealed contrary effects of Pb(II) ions on flotation recoveries of NaCl crystals and KCl crystals. Pb(II) ions strongly enhance the NaCl crystals recovery but show no considerable effect on KCl crystals recovery. Interestingly, such activation is observed exclusively for Pb(II), not for Ca, Mg, Ba, and Cu. Our analysis using XPS and XRD rules out the adsorption of lead on crystal surfaces but reveals a significant presence of lead on the collector colloids via ion substitution. In particular, we unveil a crucial role of interfacial hydrogen bonding between Pb(II) ions in the collector colloids and the outward-pointing OH groups of surface-bound water on NaCl crystals. These hydrogen bonds sustain a strong bubble-particle attraction for high recovery of NaCl crystals. No similar hydrogen bonding is possible for KCl crystals which causes a poor recovery of this salt. These insights provide hints to tailoring the flotation conditions to enable efficient separation of water-soluble minerals, which is the core interest of the potash industry.

中文翻译：

---

铅离子对脂肪酸捕收剂胶体浮选 NaCl 晶体对 KCl 晶体的独特选择性活化作用


在水溶性矿物（例如氯化钠和氯化钾晶体）的浮选中，高离子强度环境改变了典型的界面相互作用，并对传统浮选理论的适用性提出了挑战。在这里，我们报道了 Pb(II) 离子对使用月桂酸钠/钾作为捕收剂的盐水中 NaCl 和 KCl 晶体浮选的有趣影响。我们揭示了 Pb(II) 离子对 NaCl 晶体和 KCl 晶体浮选回收率的相反影响。 Pb(II) 离子强烈提高 NaCl 晶体的回收率，但对 KCl 晶体的回收率没有显着影响。有趣的是，这种激活仅在 Pb(II) 中观察到，而在 Ca、Mg、Ba 和 Cu 中则没有。我们使用 XPS 和 XRD 进行的分析排除了晶体表面上铅的吸附，但通过离子取代揭示了收集器胶体上大量存在铅。特别是，我们揭示了捕收剂胶体中的 Pb(II) 离子与 NaCl 晶体上表面结合水的向外指向的 OH 基团之间的界面氢键的关键作用。这些氢键维持了强大的气泡-颗粒吸引力，从而实现了氯化钠晶体的高回收率。 KCl 晶体不可能形成类似的氢键，这会导致该盐的回收率较差。这些见解为调整浮选条件以实现水溶性矿物的有效分离提供了线索，这是钾肥行业的核心利益。