INITIAL INVESTIGATIONS OF THE ADSORPTION OF PHOSPHATE ON KYANITE: A POSSIBLE BASIS FOR A GEOTECHNOLOGY TO MANAGE NON-POINT SOURCE POLLUTION

The modern agricultural industry is a major contributor of non-point source phosphate pollution. When phosphate enters freshwater ecosystems it has high potential to contaminate groundwater or runoff. The resulting elevated levels of phosphate can cause eutrophication and lead to dead zones in freshwater and estuarine aquatic environments. Currently there is no standard regulation to remove phosphate from natural waters, in part because of a lack of an economically viable technology to broadly mitigate phosphate pollution. Research has been conducted to investigate removal of phosphate using mineral materials such as wollastonite and fly ash. In the past, oxyhydroxide minerals have been investigated for their strong adsorptive properties so other aluminum rich minerals may be effective at removing pollution as well. In this study kyanite and mullite were investigated as a geomaterial that could adsorb phosphate and remove it from wastewater. The kyanite was obtained from the Kyanite Mining Corporation in Virginia and the samples include kyanite at five different grain sizes and mullite at five different grain sizes that the company commonly uses. Batch experiments were conducted using three different sizes of kyanite: K48 (48 mesh), K200 (200 mesh), and micronized kyanite. Four phosphate solutions were made from a stock solution using potassium phosphate salt. The concentrations were 2.5 ppm, 5 ppm, 10 ppm, and 15 ppm. Each solution was combined with a half gram of each grain size and left to mix on a shake table for 24 hours. Then triplicate samples from each bottle was run through an ion chromatograph to determine the phosphate content. The same experiment was repeated with one gram of kyanite in each of the bottles. All isotherm plots show linear adsorption. Crude removal efficiencies for all experimental conditions vary from 8% to 71%. The 200 mesh kyanite material general performed as well and sometimes better than the micronized kyanite. Work is ongoing to expand the isotherm plots to higher concentrations. Kyanite shows some promise as an aggregate geotechnology material for the removal of phosphate from freshwater.