显微-反射傅里叶变换红外光谱研究油酸钠与胶磷矿吸附机理

红外光谱已经成为浮选药剂作用机理研究的最重要手段之一。由于矿物本身具有较强的红外吸收，传统溴化钾压片透射光谱很难检测到矿物表面吸附药剂的微弱红外信号。采用显微-傅里叶变换红外光谱仪的反射模式，测定了不同浓度油酸钠在胶磷矿表面的吸附形式，并观察了吸附形貌。结果表明，与透射红外光谱相比，反射红外光谱对表面有更高的灵敏度，能更好地揭示实际浮选药剂浓度下的吸附机理。碱性条件下当油酸钠浓度较低时，油酸离子与表面晶格钙离子发生化学吸附，吸收峰在1 552 cm-1，同时也存在油酸钙沉淀的物理吸附，吸收峰在1 570和1 535 cm-1；当油酸钠浓度超过临界胶束浓度时，胶束使得胶磷矿表面亲水，导致油酸钠溶液残留在表面，吸收峰在1 560 cm-1，掩盖了其他吸收峰；表面经水洗涤后药剂吸收峰强度大幅减弱，是由于残留的油酸钠和物理吸附的油酸钙被洗掉。另外，随着油酸钠浓度增大，药剂二维形貌由点状吸附聚集为片状吸附，覆盖面积增大，但并不是完全覆盖，这与矿物表面异质性有关。以上研究结果有利于理解磷矿石提磷或铁矿石脱磷浮选体系中捕收剂与胶磷矿的作用机理。

Adsorption of Oleate on Collophane Surface Studied by Microscopic Reflectance Infrared Fourier Transform Spectroscopy

Infrared spectral analysis technology has become one of the most important research techniques in the field of action mechanism of flotation reagents. Due to the high adsorptivity of mineral, it is difficult to detect the weak signal of adsorbed reagents on mineral surface by traditional transmission infrared KBr disc spectroscopy. In this study, the adsorption form and morphology of oleate on collophane surface were measured by microscopic reflectance infrared Fourier transform at various oleate concentrations. We found that the reflectance infrared spectroscopy had greater sensitivity for adsorbed oleate species on surface when being compared with transmission infrared technique, which was more suitable to reveal the adsorption mechanism at normal flotation concentrations of oleate. The results showed that the chemisorbed oleate at a single peak of 1 552 cm-1 and calcium oleate precipitate physically adsorbed at doublet peaks of 1 570 and 1 535 cm-1 coexisted on the collophane surface at lower oleate concentration under alkaline condition. In addition, when the oleate concentration was over critical micelle concentration, the collophane surface became hydrophilic due to the adsorption of oleate micelles, which made sodium oleate solution leave on the surface, so the above peaks were covered by the sodium oleate peak of 1 560 cm-1. What’s more, the peak intensity of adsorbed oleate sharply decreased after being washed with deionized water, because the residual sodium oleate and calcium oleate precipitate physically adsorbed could be rinsed. Besides, according to the two-dimensional micrographs, with the increase of sodium oleate concentration the adsorbed oleate aggregated into the laminated structure from a dot structure, and its coverage enlarged but it was not a complete coverage. This was attributed to the surface heterogeneity. These could provide a better understanding of the interaction mechanism between oleate and collophane in the flotation of phosphate ores and high-phosphorus iron ores.