土壤颗粒对纳米TiO_2悬浮稳定性作用机制的实验研究

Experimental study on the effecting mechanisms of soil particles on the stability of TiO_2 nanoparticles

在不含表面活性剂和含有表面活性剂两种条件下,研究了土壤颗粒对纳米TiO2(nTiO2)悬浮稳定性的影响.结果表明,土壤颗粒降低了nTiO2在水相中的悬浮稳定性.当体系中不含表面活性剂时,nTiO2在土壤大颗粒上的沉积是导致nTiO2脱稳沉淀的主要原因.在含有表面活性剂的溶液中,土壤颗粒降低nTiO2悬浮稳定性的作用变得更加明显了.一方面,表面活性剂加速了土壤颗粒本身的沉降从而增强了nTiO2在其中的沉降,另一方面,表面活性剂在土壤上的强烈吸附促进了表面活性剂-nTiO2在土壤上的沉积.扫描电镜显示,nTiO2不仅吸附在土壤大颗粒上,还会吸附在土壤小颗粒表面.3种表面活性剂中,十六烷基三甲基溴化铵(CTAB)悬浮的nTiO2与土壤颗粒共沉淀现象最明显.除了土壤对CTAB的吸附作用之外,XDLVO/DLVO能量计算显示CTAB体系中土壤颗粒与nTiO2之间存在显著第二极小值,表明nTiO2能够在第二极小值位置与土壤颗粒结合,从而与土壤颗粒一起快速沉淀.

The effect of soil particles on the stability of TiO2nanoparticles(n TiO2) both in the absence and in the presence of surfactants was systematically investigated. Results showed that soil particles significantly destabilize n TiO2 in aqueous. In the absence of surfactnats,the adsorption of n TiO2 on large soil particles was mainly responsible for the destabilization and sedimentation of n TiO2. In the presence of surfactants,the destabilization of n TiO2 by soil particles was significantly enhanced. On the one hand,surfactants enhanced the sedimentation rate of soil which led to the enhanced destabilization of n TiO2. On the other hand,the large adsorption of surfactants on soil was also responsible for the co-deposition of surfactant and n TiO2 on soil. SEM showed n TiO2 did not only adsorb onto large soil particles,but also onto the fine particles. Among the three surfactants,the co-precipitation of n TiO2 with soil particles in cetyl trimethylammonium bromide(CTAB) is the most obvious. Besides the adsorption of surfactant on soil,XDLVO /DLVO energy calculation revealed a significant secondary minimum between soil particles and n TiO2,where hetero-aggregation of n TiO2 with soil would probably occur.