Colloid-Associated Contaminants Transport in Porous Media : Studies on Adsorption and Column-Flows

摘要

Colloid-associated contaminants transport in porous media is a complex phenomenon involving several basic processes such as adsorption, colloid mobilization, and colloid entrapment. The work presented here is concerned with the adsorption of contaminants such as Cu~(2+), Ni~(2+) on colloidal iron oxide and kaolin and the resulting transport of contaminants under different conditions. Batch adsorption studies indicate that Cu~(2+), Ni~(2+) metal ions adsorb strongly on the colloiadal fines, iron oxide and kaolin than on the sand materials. The adsorption process depends on pH, initial total metal ion concentration and solid adsorbent concentration. Column experimental results for Ni~(2+) transport under non-plugging and plugging conditions are presented. We find from different breakthrough curves (BTCs) for different composite packed beds that colloidal fines, Kaolin, significantly inhibits the contaminant transport and the extent of retardation increases with the increase of amount of Kaolin present in the bed as well as with the extent of plugging phenomenon. This study extends the findings of colloid-facilitated transport of contaminants and shows that there is a range of conditions under which the transport actually can be retarded. Plugging-based retardation factor, R is almost 1.5 times higher than that for non-plugging based retardation factor. Finally, calculations using an existing model are compared with measurements.