XANES Speciation of P in Environmental Samples: An Assessment of Filter Media for on-Site Wastewater Treatment

摘要

X-ray absorption near edge structure (XANES) spectroscopy is a useful technique for characterization of chemical species of phosphorus in complex environmental samples. To develop and evaluate bed filters as sustainable on-site wastewater treatment solutions, our objective in this study was to determine the chemical forms of accumulated phosphorus in a selection of promising filter materials: Filtralrte P, Filtra P, Polonite, Absol, blastfurnace slag, and wollastonite. Full-scale operational wastewater-treatment systems were sampled and in addition, filter samples collected from laboratory studies provided access to additional media and complementary samples. Phosphorus species were characterized using phosphorus K-edge XANES spectroscopy, complemented by X-ray powder diffraction (XRPDI and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR). No systematic differences could be seen in the results between laboratory-and full-scale samples. All six filter media contained significant amounts of crystalline calcium phosphates. Some samples also contained amorphous calcium phosphate (>60% of total P in Absol). In Filtralite P and blast furnace slag, more than 35% of the accumulated phosphorus was associated with Fe or Al. Both the power and shortcomings of XANES analysis for characterizing P species in these filter media are discussed.