NH_(4)^(+),F^(-)对萤石浮选的影响机理及红外光谱分析

Influence Mechanism and Analysis of Infrared Spectrum of NH_(4)^(+)and F^(-)on Fluorite Flotation

萤石浮选过程中矿浆中的NH_(4)^(+),F^(-)对萤石的可浮性有重要影响,而目前关于难免离子对浮选影响的研究主要集中在稳定的阳离子对浮选的活化或抑制作用机理,而关于不稳定阳离子(NH_(4)^(+))、阴离子(F-)影响油酸钠吸附萤石作用机制的研究较少。因此借助于红外光谱分析,结合纯矿物浮选、Zeta电位和溶液化学计算等手段,研究难免离子(NH_(4)^(+),F^(-))对油酸钠浮选萤石的作用机理。实验结果表明,在酸性条件下,NH_(4)^(+)对萤石有较强的活化作用,提高了萤石的回收率,在pH值为6时,不同NH_(4)^(+)浓度下,萤石的回收率均提高到94%左右,而在碱性条件下,NH_(4)^(+)对萤石的浮选的有一定的抑制作用,且随着pH值增加,抑制作用增强,回收率逐渐下降;但F-对萤石浮选有一定的抑制作用,且在pH值为6时,不同F-浓度的抑制作用均明显增强,导致萤石回收率降低;而在碱性条件下,F^(-)对萤石的可浮性影响不大。其作用机理为阳离子(NH_(4)^(+))与萤石表面解离到溶液中的F-生成NH 4F,在酸性条件下提高了萤石表面的正电性,增强萤石表面与油酸的一聚物、二聚物和分子-离子缔合物的吸附作用,而在碱性条件下NH_(4)^(+)的水解生成NH 3·H_(2)O,正电性降低,导致油酸钠在萤石表面的吸附作用减弱;F^(-)抑制萤石表面F-的解离,从而抑制了油酸根在萤石表面的化学吸附。红外分析结果表明,油酸钠在萤石表面发生了化学吸附;NH_(4)^(+)的加入,在酸性条件下对萤石有很强的活化作用,—CH_(3),—CH_(2)—和—COO-的特征峰峰位红移,峰强度加强,显现出较强的化学吸附作用;而在碱性条件下,仅出现了—CH_(2)—的特征峰的峰位红移,且特征峰强度减弱,说明NH_(4)^(+)在弱碱条件在萤石表面的化学吸附较弱,起抑制作用;当加入F-后只出现了—CH_(3)的反对称伸缩振动峰,峰位并未发生偏移,故F-加入后油酸钠在萤石表面并未发生任何基团的化学吸附,从而抑制了萤石的可浮性。

During the flotation process of fluorite,NH_(4)^(+)and F^(-)in the slurry have important effects on fluorite’s flotability of fluorite.At present,the research about the effects of inevitable cations on floatation mainly focus on the activation or inhibition mechanism of metal cations,but there is less research about the effect of the complex cation(NH_(4)^(+))and the anion(F-)on the adsorption mechanism of sodium oleate to fluorite.Therefore,the action mechanism of NH_(4)^(+)and F^(-)on fluorite flotation by sodium oleate is studied in this paper by means of infrared spectroscopy analysis,combined with the flotation experiment of pure fluorite,Zeta potential and solution chemical calculation.The results show that NH_(4)^(+)has a strong activation effect on fluorite and increases the recovery rate of fluorite under acidic condition,and when the pH value is 6,the recovery of fluorite increased to about 94%at different NH_(4)^(+)concentrations.However,under alkaline conditions,NH_(4)^(+)had a certain inhibitory effect on fluorite flotation,and the recovery rate decreased gradually with the increase of pH value.But F^(-)inhibits fluorite to some extent,when the pH value is 6,the inhibitory effect of different F^(-)concentrations is significantly enhanced,resulting in a decrease of fluorite recovery.However,under alkaline conditions,F^(-)has little influence on the flotability of fluorite.The action mechanism is that the adsorption of the cation(NH_(4)^(+))and F^(-)dissociated from fluorite surface in solution form NH 4F under acidic conditions to improve the electropositivity of fluorite surface,and enhance the adsorption between fluorite surface andmonomer,dimer and acidmolecule-ion association of oleic;while under alkaline conditions,the hydrolysis of NH_(4)^(+)results in the formation of NH 3·H_(2)O,which reduces the positive electrical properties and leads to the weakening of the adsorption of sodium oleate on the fluorite surface.F^(-)inhibits the dissociation of F^(-)on fluorite surface,thus inhibiting the chemisorption of oleate acid ion on fluorite surface.FT-IR analysis results show that the chemisorption occurred between sodium oleate and fluorite surface.NH_(4)^(+)had a strong activation effect on fluorite surface under acidic conditions because the characteristic peaks of—CH_(3),—CH_(2)—,—COO-are red-shifted and their peak intensity is enhanced,showing a strong chemisorption effect.However,under alkaline conditions,only the characteristic peak of—CH_(2)—appears red shift,and the intensity of the characteristic peak is weakened,indicating that under weak alkali conditions,the chemisorption of NH_(4)^(+)on the fluorite surface is weak and inhibited the adsorption.When F^(-)is added,only the antisymmetric expansion vibration peak of—CH_(3)appears and no red shift of the peak position has occurred.Therefore,no chemisorption of any group on the fluorite surface occurs after the addition of F^(-),which inhibits the flotability of fluorite.