Study of the Physical-Chemical Mechanisms and Variables Which Affect the Transport of Inorganic and Organic Contaminants in Heterogeneous System: Final Report.

摘要

This research defines reaction mechanisms and key variables that account for distribution or partitioning of inorganic and organic solutes between the aqueous solution and solid phase adsorbents. The ultimate goal is to develop improved understanding of chemical equilibrium or kinetic rate dependencies which are important in predicting the movement of microcontaminant species in subsurface environments. The adsorbent chosen for study is goethite with emphasis largely on the protolyzable anions (arsenate, selenite and phosphate) and organics (benzoic acid, phenol and derivatives). We have also been concerned with proton behavior in these systems. The experimental approach uses batch adsorbate-adsorbent systems that are analyzed in time against changes imposed by altering adsorbate concentration, pH, ionic strength, and solid/solution ratios, as well as the adsorbent itself. Results are interpreted in terms of mechanisms consistent with the physical-chemical behavior of a heterogeneous colloid suspension. Major progress includes: (1) a descriptive mechanism for decreasing isotopic exchange with increasing adsorption, and effect of solid/liquid ratio in adsorption processes; (2) equilibrium description of pH and charge effects on strongly versus weakly bound anions; and (3) a mathematical description of the entropic forces in interfacial reactions. (ERA citation 14:003543)