(540c) Thermal Vapor Deposition of a Hydrophobic and Gas-Permeable Membrane on Zirconium Phosphate Cation Exchanger: An Oral Sorbent for Urea Removal of Kidney Failure

An oral sorbent with high capacity for NH₄⁺ is desirable in lowering blood urea level and mitigate the dialysis burden for end stage kidney disease (ESKD) patients. Zirconium phosphate (ZrP) is an amorphous cation ion exchanger with high NH₄⁺ binding capacity as a sorbent material, but its selectivity to remove NH₄⁺ is limited in presence of other competing ions in water solution. We previously have developed a gas-permeable and hydrophobic perfluorocarbon coating on ZrP, which improves ZrP’s NH₄⁺ selectivity. However, the coating preparation procedure, a wet chemistry approach, is complicated and time-consuming, and more importantly, the large amount of usage of acetone poses a concern for the application of ZrP as an oral sorbent. In this study, we developed a solventless coating protocol that effectively coats ZrP with Tetraethyl orthosilicate (TEOS) and 1H,1H,2H,2H-Perfluorooctyltriethoxysilane (FOTS) via thermal vapor deposition (TVD) in a simplified manner. X-ray photoelectron spectroscopy (XPS) and contact angle measurements verify the two coating precursors are successfully deposited on ZrP surface which shows a water contact angle of ~142°. In vitro competing ion studies show significant improvement in NH₄⁺ binding capacity and selectivity over Ca²⁺ with TVD coatings on ZrP. The findings here establish a highly promising surface modification approach to optimize oral sorbents for ESKD patients.

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