Sorption of Humic Materials onto Inorganic Surfaces for the Mitigation of Facilitated Pollutant Transport Processes

The transport of hydrophobic organic pollutants in groundwaters is facilitated by sorption of these chemicals onto natural organics and transport with these materials. One strategy to mitigate pollutant transport through clay liners and slurry walls is to reduce the transport of the natural organics by enhancing their sorption onto the containment barrier materials. A controlled experimental study of the adsorption of humic acid onto typical inorganic constituents of soils was performed using two types of model solid phases: 1) pure solids (washed Na-montmorillonite clay, amorphous ferrihydrite, and amorphous aluminosilicate gel) and 2) binary combined phases (Na-montmorillonite coated with ferrihydrite or aluminosilicate gel). The combined phases were synthesized for a range of metal to clay mineral ratios. Adsorption tests were conducted to investigate the relative sorption affinity of these solid phases for humic acid. Addition of a ferrihydrite coating was found to increased the sorption of humic acid onto montmorillonite clay.