Dialysate regeneration via urea photodecomposition with TiO nanowires at therapeutic rates.

BACKGROUND

The standard weekly treatment for end-stage renal disease patients is three 4-h-long hemodialysis sessions with each session c'onsuming over 120 L of clean dialysate, which prevents the development of portable or continuous ambulatory dialysis treatments. The regeneration of a small (~1 L) amount of dialysate would enable treatments that give conditions close to continuous hemostasis and improve patient quality of life through mobility.

METHODS

Small-scale studies have shown that nanowires of TiO are highly efficient at photodecomposing urea into CO and N when using an applied bias and an air permeable cathode. To enable the demonstration of a dialysate regeneration system at therapeutically useful rates, a scalable microwave hydrothermal synthesis of single crystal TiO nanowires grown directly from conductive substrates was developed. These were incorporated into 1810 cm flow channel arrays. The regenerated dialysate samples were treated with activated carbon (2 min at 0.2 g/mL).

RESULTS

The photodecomposition system achieved the therapeutic target of 14.2 g urea removal in 24 h. TiO electrode had a high urea removal photocurrent efficiency of 91%, with less than 1% of the decomposed urea generating NH (1.04 μg/h/cm ), 3% generating NO and 0.5% generating chlorine species. Activated carbon treatment could reduce total chlorine concentration from 0.15 to <0.02 mg/L. The regenerated dialysate showed significant cytotoxicity which could be removed by treatment with activated carbon. Additionally, a forward osmosis membrane with sufficient urea flux can cut off the mass transfer of the by-products back into the dialysate.

CONCLUSION

Urea could be removed from spent dialysate at a therapeutic rate using a TiO based photooxidation unit, which can enable portable dialysis systems.