UTILIZING GEOPOLYMERS AS CONTROL-RELEASE MECHANISMS FOR OXIDANT DELIVERY

Contamination of groundwater by chlorinated ethylenes (i.e. trichloroethylene (TCE), dichloroethylene (DCE), and perchloroethylene (PCE)) is prevalent and problematic at many industrial and military sites around the world. Our focus here is with potassium permanganate (KMnO₄) which has been established to be a cheap and effective oxidant. Geopolymers are inorganic polymers that consist of alumino-silicate materials, which can be obtained from metakaolin or industrial byproducts such as fly ash or blast furnace slag. The geopolymerization process involves an integration of the alumino-silicate oxides with sodium metasilicate under highly alkaline conditions. Once mixed the polymer (as a paste) is poured into steel molds and are cured at temperatures less than 70⁰ C. This reaction produces an amorphous to semi crystalline alumino-silicate structure. We have produced variations of these polymers containing KMnO₄.The release rates of KMnO₄ were studied by a series of column experiments. Three geopolymer samples each bearing 10 grams, 35 grams, and 50 grams are each placed into a glass column (Chromaflex, Kontes) (4.8cmX15 cm) connected to a peristaltic pump (Ismatec Ecoline) supplying an ambient flow of water of 22 mL/min^-1. Samples were taken from discharge of column and analyzed via UV-VIS photo spectrometer (Shimadzu UVmini-1240) for absorbance and thus correlated to concentration of KMnO₄ released. With increasing amount of KMnO₄ the lifetime of the geopolymer also increased. Geopolymers are classified as glassy polymers which do not follow fickian diffusion. Non-fickian diffusion consists of Case II transport and anomalous diffusion. The data from these series of experiments was modelled mathematically according to “non-fickian“diffusion. Geopolymers possess great potential for the remediation of groundwater plumes because of their inherent resistance to oxidation by KMnO₄. This makes them prime candidates for acting as control release solids for dispersing the KMnO₄ within the aquifer. Ideally KMnO₄ can strategically be injected into groundwater system though boreholes, once in place, time-delayed diffusion of KMnO₄ will act as a reactive barrier system isolating and destroying the ethane plume.