School of Minerals Processing and Bioengineering, Central South University, Changsha410083, China.
Hunan Provincial Key Laboratory of Complex Copper Lead Zinc Associated Metal Resources Comprehensive Utilization, Hunan Research Institute for Nonferrous Metals, Changsha410100, China.
Langmuir. 2023 Feb 14;39(6):2182-2191. doi: 10.1021/acs.langmuir.2c02651. Epub 2023 Jan 30.
Quartz, a common inorganic nonmetallic mineral, is usually removed or purified by beneficiation, normally flotation. Given the strong polarity of the quartz surface, it is easy to hydrate to form a hydroxylation layer, which makes it impossible to float quartz with sodium oleate (OL) used alone. An ideal flotation method for quartz is preactivation with Ca, followed by collection with OL. Herein, the effects of surface hydroxylation on the adsorption of the anionic collector OL on the quartz surface before and after Ca activation are systematically investigated by density functional theory (DFT) calculations. The results show that the displacement adsorption of surface hydroxyl substituted by OL is not feasible in thermodynamics, and the OL can only bind to the H atoms of the hydroxylated quartz surface via hydrogen bonds, namely, hydrogen binding adsorption. Due to the electrostatic repulsion and steric hindrance effect induced by the surface hydroxylation structure, the adsorption ability of OL on the quartz surface mediated by hydroxyl bridges is very weak, which is insufficient to realize quartz floating. However, Ca ions are easily adsorbed on the hydroxylated quartz surface, providing favorable active sites for subsequent adsorption of OL, thus becoming a credible solution for the industrial flotation of the strong hydrophilic mineral quartz. These findings shed some new insights for accurately understanding the flotation mechanism of strongly hydrophilic oxide minerals and are beneficial to promoting the development of mineral flotation fundamentals.
石英是一种常见的无机非金属矿物，通常通过选矿（通常是浮选）来去除或提纯。鉴于石英表面的强极性，它很容易水合形成羟基化层，这使得单独使用油酸钠（OL）浮选石英变得不可能。对于石英来说，一种理想的浮选方法是先用 Ca 进行预活化，然后再用 OL 进行收集。本文通过密度泛函理论（DFT）计算系统研究了表面羟基化对 Ca 活化前后阴离子捕收剂 OL 在石英表面吸附的影响。结果表明，OL 取代表面羟基的置换吸附在热力学上是不可行的，OL 只能通过氢键与羟基化石英表面的 H 原子结合，即氢键吸附。由于表面羟基化结构引起的静电排斥和空间位阻效应，羟基桥介导的 OL 在石英表面的吸附能力非常弱，不足以实现石英浮选。然而，Ca 离子很容易被吸附在羟基化的石英表面上，为随后 OL 的吸附提供了有利的活性位，从而为工业浮选强亲水矿物石英提供了可靠的解决方案。这些发现为准确理解强亲水氧化物矿物的浮选机制提供了一些新的见解，有利于促进矿物浮选基础理论的发展。
