31-19 Initial Investigations of Combined Hydrotalcite - Sepiolite Reactive Media for Developing Phosphate Remediation and the Reduction in Nutrient Runoff

Session: Environmental Geochemistry and Health (Posters)

Poster Booth No.: 45

Presenting Author:

Geneva Uhlenbrock

Authors:

Uhlenbrock, Geneva¹, Belak, Ethan², Gray, Morgan³, Krekeler, Mark P. S.⁴

(1) Geology and Environmental Science, Miami University, Oxford, Ohio, USA, (2) Geology and Environmental Science, Miami University, Oxford, OH, USA, (3) Geology and Environmental Science, Miami University, Oxford, OH, USA, (4) Geology and Environmental Science, Miami University, Oxford, OH, USA,

Abstract:

Agricultural runoff and nutrient pollution are a growing issue, with roughly 5 million tons of phosphorus used in the United States annually. This runoff leads to eutrophication and water quality issues. This has led to pressure on both landowners to use less fertilizer and other agencies to find ways to mitigate the effects of nutrient pollution. Phosphorus is generally the limiting nutrient in freshwater systems and has lower mobility compared to other nutrients like nitrogen. Phosphorus readily binds to many minerals, most notably goethite, with this interaction being studied extensively. In previous studies, synthetic hydrotalcite and thermally modified sepiolite have been used to adsorb phosphorus and reduce bioavailable levels, presenting an opportunity for a mitigation strategy. However, the effectiveness of phosphorus fixation and stabilization in joint conditions has not been investigated. A pure sample of both hydrotalcite and sepiolite, along with 20:80, 80:20, and 50:50 mixtures, is being initially investigated by using varying phosphorus solutions and anion concentrations. Pre- and post-adsorption water compositions are measured via ion chromatography. Phosphorus solutions were generated via the addition of potassium dihydrogen phosphate to concentrations of between 0 and 10 mM; calcium chloride was also added for a constant background electrolyte concentration. Mineralogy of both hydrotalcite and sepiolite materials was confirmed via X-ray diffraction and limited study via electron microscopy. While this is still in a preliminary stage, it is expected that hydrotalcite will have higher phosphorus adsorption on its own compared to sepiolite. But the mixture will likely have a higher overall adsorption over time in flow conditions due to the sepiolite providing more surface area and reducing hydrotalcite loss. This has potential implications for developing phosphate remediation and the reduction in nutrient runoff capabilities.

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