TiO₂ Nanowires Based System for Urea Photodecomposition and Dialysate Regeneration

Abstract

To enable portable kidney dialysis for end-stage renal disease, the regeneration of the dialysate in a closed loop system is a critical technical barrier. Currently dialysis treatment uses ∼120 L of dialysate per 4 h session, to remove urea as well as other toxins from the blood, far exceeding usable weights for a portable system. We have developed an efficient photooxidation system based on hydrothermally grown TiO2 nanowires, UV LEDs, and catalytic gas diffusion barriers to decompose urea from the dialysate at rates sufficient to remove daily production of urea at 15 g/day. With 365 nm LED irradiation of 4 mW/cm2, dialysate simulant solutions of 10 mM urea/0.15 M NaCl photocurrent density of ∼1 mA/cm2 was achieved, corresponding to 40% quantum efficiency in urea decomposition per incident photon. From performance parameters, a feasible portable device with 0.23 m2 active area and a current draw of 11 A is able to decompose a daily 15 g urea production sufficient to regenerate dialysate.

Dialysate Regeneration with Urea Selective Membrane Coupled to Photoelectrochemical Oxidation System

“…POUR Device Assembly and Testing: TiO 2 coated FTO/borosilicate substrates were prepared hydrothermally following previous procedures. [20,38] 4 mg cm −2 Pt black-coated carbon paper was purchased from the Fuel Cell Store (#1610009-1). FTO on borosilicate glass slides (2.54 cm × 7.62 cm) was purchased from MTI corporation (FTO257630TEC7gp25).…”

“…[17,18] Oxidation based urea removal has been shown to be efficient and led to the production of gaseous products of N 2 and CO 2 . [19,20] We have previously developed a photo-oxidation urea removal (POUR) device to remove urea. By using hydrothermally prepared, randomly oriented, single crystalline TiO 2 nanowire meshes coated onto fluorinated tin oxide (FTO) conductive substrates, we have achieved a ≈500× increase in the urea removal rate.…”

“…By using hydrothermally prepared, randomly oriented, single crystalline TiO 2 nanowire meshes coated onto fluorinated tin oxide (FTO) conductive substrates, we have achieved a ≈500× increase in the urea removal rate. [ 20 ] The daily production of 15 g of urea can be removed using a practical‐sized active surface area of 2360 cm. [ 2 ] However, the byproducts from the incomplete oxidation of other chemicals, particularly glucose, could pose challenges to the safety of the portable dialysis device.…”

The Roles of Membrane Technology in Artificial Organs: Current Challenges and Perspectives

“…An ideal WAK devices should weigh under 8 kg and the total volume should be less than 0.1m 3 [ 164 ]. Several urea removal strategies have been reported in the WAK such as sorbents [ 165 ], photo-oxidation [ 166 ] and electro-oxidation [ 167 ]. An exciting work that applies artificial intelligence (AI) techniques to improve dialysis therapy has been reported by real-time feedback responses and life and death making decisions [ 168 , 169 ].…”

How artificial kidneys and miniaturized dialysis could save millions of lives

“…In Seattle, CDI researchers have developed a technique that pushes the used dialysis solution through a cartridge that uses light to convert urea -a key toxin targeted by dialysis -into nitrogen and carbon dioxide, so that the solution can be recycled 3 . The method can remove 15 grams of urea in 24 hours, sufficient for most people with kidney failure, and requires only 750 millilitres of solution, Himmelfarb says.…”