Transport of TiO2 nanoparticles in soil in the presence of surfactants.

This paper aimed to investigate the influences of surfactants on the nanoparticle transport behavior in soil. The transport behaviors of TiO2 nanoparticles (nTiO2) in soil with three different surfactants, including Triton X-100 (TX-100), sodium dodecylbenzene sulfonate (SDBS) and cationic cetyl trimethylammonium bromide (CTAB) were studied. Results showed that all the three surfactants decreased the mobility of nTiO2 in soil column, which were mainly caused by the strong adsorption of surfactants on soil and nTiO2. The inhibition order was as follows: CTAB>SDBS>TX-100. Combined effect experiments showed that when solution ionic strength (IS) increased, TX-100 or CTAB inhibited the mobility of nTiO2 in soil. However, the effect of SDBS on nTiO2 transport shifted from inhibition to facilitation when IS increased from 0.1 to 5mM. This was mainly attributed to the decreasing adsorption of SDBS on soil with increased IS, whereas the adsorption of TX-100 and CTAB was independent of IS. This innovative information motivates further insight into the role of surfactants on nanoparticle transport behavior in soil.