Scalable fabrication of cellulose/zirconium phosphate hydrogel spheres for portable dialysis cartridges

The sorbent dialysis system has emerged as one of the most promising research directions in wearable artificial kidneys (WAK), owing to its substantially lower water consumption compared to conventional hemodialysis (reduced from 120 L to 6 L per treatment). These systems typically incorporate multilayer adsorption cartridges, where zirconium phosphate (ZrP) serves as the critical component for eliminating urea-derived ammonium ions (NH₄ + ). However, the inherent lamellar structure of ZrP induces material stacking, resulting in elevated column pressure during operation - a significant limitation that hinders broader clinical adoption. In this study, we developed a novel methodology for fabricating ZrP composite hydrogel spheres with high NH₄ + removal capacity. We first demonstrate that thermal treatment facilitates the intercalation of ionic liquid into α-ZrP interlayers, resulting in expanded interlayer spacing. This structural modification enhances subsequent Na + ion exchange and further optimizes the NH₄ + exchange capacity, representing a 5-fold improvement over untreated α-ZrP. Next, we engineered a structural matrix by using cellulose nanofibers (CNFs) to host ZrP nanoplates. Through an ionic liquid-assisted synthesis strategy, we simultaneously achieved CNF regeneration and ZrP intercalation, producing CNF/ZrP composite hydrogel spheres. These spheres address layer restacking while improving mechanical robustness and ion exchange performance. The resulting CNF/ZrP spheres also exhibit superior column-packing characteristics, achieving 88.7 % overall NH₄ + removal efficiency (6.41 mg g ZrP −1  min −1 ) from a 12 mL physiological saline solution in the model flow system. This study establishes CNF/ZrP hydrogel spheres as a promising sustainable adsorbent platform for next-generation dialysis cartridges.