Facile synthesis of high-performance crystalline zirconium phosphate adsorbents and its ammonium ion intercalation mechanism for next-generation hemodialysis

Conventional hemodialysis significantly impacts patients' quality of life due to its intermittent nature, thus creating a demand for portable (PAK) or wearable artificial kidneys (WAK). A critical challenge in these systems is the efficient regeneration of dialysis fluid, which relies on cost-effective, high-performance adsorbents. This study introduces a novel sol-gel synthesis method for producing high-crystalline layered zirconium phosphate (ZrP) as adsorbents by incorporating fluoride ions and utilizing thermal treatment. This approach streamlines large-scale production while addressing the cost and complexity barriers of traditional ZrP synthesis, which also avoids the high temperatures and pressures typically required. The as-prepared α-Zr (HPO 4 ) 2 ⋅H 2 O (abbr. α-H 2 ZP) demonstrates an exceptional ammonium ion (NH 4 ⁺) adsorption capacity of 6.46 mmol/g for ammonium carbonate, surpassing α-Zr(NaPO 4 ) 2 ⋅H 2 O (abbr. α-Na 2 ZP) by 28 %. Moreover, α-H 2 ZP minimizes sodium leaching during adsorption, a critical advantage for dialysis fluid regeneration. Furthermore, adsorption mechanism studies revealed that the alkaline environment generated by ammonium salt hydrolysis triggers interlayer expansion in α-H 2 ZP, thereby enhancing NH 4 ⁺ insertion. In contrast, α-Na 2 ZP exhibits limited responsiveness to changes in anion concentration, highlighting α-H 2 ZP's superior adaptability. These findings position α-H₂ZP as a promising candidate for next-generation hemodialysis technologies, providing a foundation for the development of miniaturized, lightweight, and cost-effective WAK/PAK devices.