非离子表面活性剂的吸附机理和表面胶团化对二氧化硅悬浮液稳定性的影响

测定了CAB-O-SIL在290.7K和304.2K时自水和1mol/LNaCl溶液中吸附非离子表面活性剂TritonX-100(TX100)的吸附等温线。结果表明,吸附量随温度升高而增加。NaCl的存在也使吸附量增加。运用生成表面胶团的吸附理论处理了实验结果,求得了表面胶团化的平衡常数、表面胶团的平均聚集数、临界表面胶团浓度和表面胶团化的标准热力学函数。实验表明,随TX100浓度的增大,CAB-O-SIL悬浮液稳定性出现不规则的变化。加入NaCl的效应是使悬浮液的稳定性下降和促进表面胶团的形成。结合吸附研究结果,提出了一个涉及表面胶团的颗粒相互作用模型,合理地解释了悬浮液稳定性的实验结果。

The Mechanism of Adsorption of Nonionic Surfactants on CAB-O-SIL and the Effects of Surface Micellization on the Stability of Silica Suspension

The adsorption isotherms of Triton X-100(TX 100) on a flamehydrolyzed silica (CAB-O-SIL) from aqueous solutions and from sodium chloride(1.0 mol/L) at 290.7K and304.2 K have been determined.The results show that the adsorption increases with increasing temperature and salinity.Based on the theory of surfactant adsorption we proposed previously,the equilibrium constant of surface micellization(K),surface micelle aggregation number(n_(sm)),surface micelle concentration(smc) and the standard thermodynamics functions of surface micellization are calculated.The results show the value of n_(sm) increases with increasing temperature,In addition,similar to the micellization in bulk solution,the surface micellization is also an entropy-driven process.The effects of TX100(with or without 1.0 mol/L sodium chloride) on the aggregative stability of silica suspension have also been investigated. In the low concentration range of TX 100, the stability of suspension increases with increasing concentration of TX 100.Above the surface micelle concentration(smc) of TX 100, the stability of suspension decreases with increasing concentration of TX 100. However if the concentration approaching to the cmc of TX 100,the stability of suspension increases again,The addition of sodium chloride enhances the surface micelle formation and results in a depression of stability of suspension,Based on the adsorp tion isotherms of TX 100,a model concerning surface micellization is proposed to explain the above experimental results reasonably.