稀土矿浮选中Ce^(3+)对萤石的活化作用机理

Activation mechanism of Ce^(3+) on fluorite in rare earth ore flotation

通过纯矿物浮选、Zeta电位测试、溶液化学计算、红外光谱分析及XPS测试,研究以羟肟酸为捕收剂浮选稀土时Ce^(3+)离子对萤石的活化作用机理。结果表明:矿浆中Ce^(3+)离子浓度低于羟肟酸时在p H 6~12对萤石都具有活化作用,其活化机理为Ce^(3+)离子吸附提高萤石表面的正电性,增强萤石表面与阴离子羟肟酸捕收剂的静电吸附作用,且在萤石表面形成F-Ce(OH)_2/Ce(OH)^+活性位点。红外光谱和XPS测试表明,无Ce^(3+)离子活化时,辛基羟肟酸在萤石表面主要生成不稳定的四元环络合物—C—O—Ca—N—,羟肟酸与Ca^(2+)离子结合能小,直接在萤石表面的吸附作用弱;被Ce^(3+)离子活化后,辛基羟肟酸与萤石表面Ce^(3+)离子反应生成稳定的五元环络合物—C=O—Ce—O—N—,羟肟酸与Ce^(3+)离子结合能大,加强羟肟酸在萤石表面的吸附作用,从而使萤石被活化。

The activation mechanism of Ce3＋ on fluorite using octanohydroxamic acid （OHA） as rare earth flotation collector was studied by pure mineral floatation experiment, Zeta potential measurement, solution chemistry analysis, infrared（ IR） spectra and XPS measurements. The results show that fluorite can be activated at pH 6-12 when the concentration of Ce3＋ is lower than that of OHA, the activation mechanism is that the positive potential of fluorite is improved by adsorbing of Ce3＋onto its surface, thus enhancing the electrostatic adsorption of anionic hydroxmic acid collector on fluorite, and moreover F-Ce（OH）2/Ce（OH）＋ active site can be formed on the surface of fluorite. IR spectra and XPS measurements show that an unstable four-member ring chelate complex -C-O-Ca-N- is generated when OHA reacts with fluorite without Ce3＋ activation, the binding energy of OHA with Ca2＋ is low, which leads to a weak adsorption of OHA onto fluorite. A stable five-member ring chelate complex -C=O-Ce-O-N- forms when OHA reacts with Ce3＋ activated fluorite, the binding energy of OHA with Ce3＋ is high, which enhances the adsorption of OHA onto fluorite and thus activates the flotation of fluorite.