阳离子表面活性剂与高岭石的相互作用机理

采用十二胺阳离子表面活性剂为捕收剂,考察了高岭石的可浮性随pH值的变化情况.通过对高岭石不同解理面的化学组成分析及其与十二胺作用的量子化学计算分析,建立了高岭石在不同pH值条件下与十二胺的作用模型,解释了阳离子作用下高岭石的浮选行为.碱性矿浆中,高岭石颗粒的端面和层面均带负电,各解理面间产生静电斥力而使矿粒充分分散;阳离子十二胺在高岭石的(001)面优先吸附,使高岭石的各表面亲水性不同,从而在亲水力的作用下使颗粒发生疏水絮凝,减少了矿物的疏水表面,使矿物难以被浮选.在酸性条件下,矿浆中存在大量游离的离子,高岭石的(001)面吸附H 而使其表面性质与{001}面性质相似,十二胺能够较均匀地吸附在高岭石的各个解理面上.此外,高岭石颗粒的端面带正电,层面带负电,二者之间静电引力作用使矿粒发生絮凝,减少了高岭石矿粒的总表面积,增加了捕收剂的吸附密度.2种因素共同作用,使高岭石在pH值较低的矿浆中表现出较好的可浮性.

Mechanism of interaction between cationic surfactant and kaolinite

The floatability of kaolinite was investigated in the presence of dodecylamine(DDA).Based on the analysis of chemical composition of each kaolinite cleavage plane and the quantum calculation of interaction between kaolinite surfaces and DDA,the interaction model under diverse pH values was constructed to explain the special flotation behavior of kaolinite in the presence of cationic surfactant.In alkaline pulp,the mineral powders can be fully dispersed in the suspension owning to negative charge held by both side and bottom surface of kaolinite crystal. The cationic surfactant DDA has the adsorption priority on the (001) surface of kaolinite resulting in the varying hydrophilic of different surfaces of kaolinite.Triggered by intensive hydrophilic force of mineral powder,hydrophobic flocculation occures, then the hydrophobic surface areas are reduced greatly and followed by the increased difficulties of mineral flotation. In acid pulp,dodecylamine can be fairly adsorbed on each surfaces of kaolinite for the similar surface properties of (001) surface and {001} resulted from the H~ adsorption on the bottom surface. And the adsorptive density of collector is well increased for the decreased total surface areas of kaolinite powders as a result of the flocculation caused by the positive charge and the negative charge held by side and bottom surface respectively.Thus the kaolinite flotation rate could keep a relatively high level under lower pH values condition.