Sun Kangkang, Nguyen Cuong V, Nguyen Ngoc N, Ma Xiaozhen, Nguyen Anh V
School of Chemical Engineering, The University of Queensland, Brisbane, Queensland 4072, Australia.
School of Chemical Engineering, The University of Queensland, Brisbane, Queensland 4072, Australia.
J Colloid Interface Sci. 2023 Apr 15;636:413-424. doi: 10.1016/j.jcis.2023.01.038. Epub 2023 Jan 9.
Flotation of water-soluble KCl and NaCl minerals in brines is significant for K-fertilizer production, but its mechanism is controversial. Dissolved salt ions are expected to change the physicochemical properties of solvents, interfaces, and collector colloids, thereby affecting flotation significantly.
Flotation experiments of KCl and NaCl crystals in brines were conducted using potassium and sodium laurates as collectors. Contact angle (CA) and surface tension measurements, X-ray photoelectron spectroscopy (XPS) analysis, and molecular dynamics simulations (MD) were applied to gain a molecular understanding of changing interfacial properties and crystal-collector colloid interactions in the presence of dissolved ions in terms of salt flotation.
While K ions activate the NaCl crystal flotation, Na ions depress the KCl crystal flotation, in agreement with the studies of CA, XPS, and MD results with these crystals. XPS results showed no collector adsorption at crystal surfaces which is a requirement of conventional flotation and presents a new theoretical challenge. We argue the crucial role of ion specificity: Na-laurate colloids adsorb at the bubble surface as a monolayer but solvent-separated from KCl crystals, inhibiting their flotation, or in interactive contact with NaCl crystals, enhancing their flotation. Increasing K concentration weakens NaCl crystal hydration, increasing Na-laurate colloid attraction with crystals for better flotation. The Contact Interactive Collector Colloid (CICC) and Solvent-separated Interactive Collector Colloid (SICC) hydration states are critical to salt crystal flotation via collector colloid-crystal attraction by dispersion forces.
水溶性氯化钾和氯化钠矿物在卤水中的浮选对钾肥生产具有重要意义，但其机理存在争议。溶解的盐离子预计会改变溶剂、界面和捕收剂胶体的物理化学性质，从而显著影响浮选。
以月桂酸钾和月桂酸钠为捕收剂，进行了氯化钾和氯化钠晶体在卤水中的浮选实验。应用接触角（CA）和表面张力测量、X射线光电子能谱（XPS）分析以及分子动力学模拟（MD），从盐浮选的角度，对溶解离子存在时界面性质的变化以及晶体 - 捕收剂胶体相互作用进行分子层面的理解。
钾离子能活化氯化钠晶体浮选，而钠离子则抑制氯化钾晶体浮选，这与对这些晶体的接触角、XPS和MD结果的研究一致。XPS结果表明在晶体表面没有捕收剂吸附，这是传统浮选的一个必要条件，并且提出了一个新的理论挑战。我们认为离子特异性起着关键作用：月桂酸钠胶体以单层形式吸附在气泡表面，但与氯化钾晶体被溶剂隔开，抑制其浮选，或者与氯化钠晶体相互接触，增强其浮选。增加钾离子浓度会减弱氯化钠晶体的水化作用，增强月桂酸钠胶体与晶体的吸引力，从而实现更好的浮选。接触式相互作用捕收剂胶体（CICC）和溶剂分离式相互作用捕收剂胶体（SICC）的水化状态对于通过分散力实现捕收剂胶体 - 晶体吸引力的盐晶体浮选至关重要。
