Performance of a Functionalised Polymer-Coated Silica at Treating Uranium Contaminated Groundwater from a Hungarian Mine Site

摘要

The performance of a recently developed active material for treating uranium contaminated groundwater within a permeable reactive barrier (PRB) is reported. This material, PANSIL, is an example of a tailored ligand system that selectively removes the contaminant from solution. The active medium is a polyacryloamidoxime resin derived from polyacrylonitrile, which is deposited from solution onto the surface of quartz sand to form a thin film coating. PANSIL is effective at sequestering cationic and neutral uranyl species when the solution pH is above 4, due to the stability of the polyacryloamidoxime-uranyl complex formed. However the rate of sequestration decreases rapidly when the pH exceeds about 8 where neutral uranyl species are present only at very low concentrations. PANSIL can preferentially sequester UO_2~(2+) in the presence of divalent groundwater cations. In mildly alkaline conditions performance is very sensitive to the concentration of uranyl complexing ligands, such as bicarbonate, which affect the sequestration rate. Such behaviour has important consequences for PRB design as it will determine the barrier thickness required for a particular flow rate.