The Colloidal Stability of Imogolite and Their Breakthrough Behavior in Toyoura Sand Packed Column

Abstract

The influence of pH and ionic strength on transport properties of imogolite particles through porous media were investigated by column experiments. Imogolite suspensions varying in pH and NaCl concentration were flowed into the column packed with Toyoura standard sands. Breakthrough behavior of imogolite was affected by their colloidal stability. That is, at low pH or low NaCl concentration, where imogolite particles were dispersed, the effluent concentration of imogolite rapidly reached to that of influent, indicating that the particles were not significantly captured in the column. On the other hand, at higher pH value or higher NaCl concentration, where  imogolite particles were aggregated, the effluent concentration of imogolite was lower. We consider that the imogolite deposited on the sands are able to capture suspended imogolite in pore fluid and thus reduce the effluent concentration. In pH 6.4, at which imogolite are in the transition condition between dispersion and aggregation, the onset of breakthrough was delayed 2 pore volume at NaCl concentration I=1.0×10^-2 M. The delay period was longer under the higher ionic strength condition.