Zero-valent iron colloid emplacement in sand columns

Studies were conducted to evaluate a novel approach of emplacing chemically reactive barriers composed of zero-valent iron (Fe-0) by injecting suspensions of colloidal-size Fe-0 particles into porous media. The specific objective of this study was to evaluate the effect of influent colloid concentration, rate, and volume of colloidal suspensions on Fe-0 colloid emplacement in sand columns. Relatively even distributions of Fe-0 throughout a sand column were obtained at low influent colloid concentrations and high injection rates. As the concentration of influent suspension was increased, a point was reached beyond which a significant increase in the filtration of Fe-0 particles near the front of the column was observed. This point was also found to occur at lower influent colloid concentrations as the injection rate was decreased, i.e., there was an interactive effect of influent colloid concentration and injection rate on the extent of filtration that occurred near the front of the column. As the volume of the colloidal suspension injected into the column was increased, the distribution of Fe-0 colloids within the column became increasingly even.