Efficient urea removal using dialdehyde microcrystalline cellulose for dialysate regeneration in wearable artificial kidneys.

The wearable artificial kidney (WAK) offers a promising alternative to hemodialysis for end-stage renal disease, depending on efficient dialysate regeneration for continuous operation. Herein, dialdehyde microcrystalline cellulose (DMC) was prepared by periodate oxidation of microcrystalline cellulose (MCC) and evaluated for its urea adsorption performance and underlying mechanism in dialysate. The structure of the DMC was characterized using scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy and optical microscopy. Batch adsorption studies indicate that the equilibrium urea adsorption capacity increased with increasing aldehyde content of DMC, reaching a maximum of 90.3 ± 7.5 mg/g. FTIR, Raman, and solid-state nuclear magnetic resonance analyses suggest that urea adsorption involves hydrogen-bonding interactions and formation of Schiff base linkages. Thermogravimetry-FTIR-mass spectrometry analysis supports the proposed adsorption mechanism and provides important information for the safe disposal of spent adsorbents. Under fixed-bed column conditions simulating WAK operation, DMC achieved a maximum urea removal efficiency of 73.8 ± 1.7% within 120 min, markedly higher than that of native MCC (40.5 ± 5.5%). Our findings suggest that DMC is a promising candidate adsorbent for WAK devices.