Catalytic urea electrooxidation on nickel-metal hydroxide foams for use in a simplified dialysis device

Electrocatalytic urea removal is a promising technology for artificial kidney dialysis and wastewater treatment. Urea electrooxidation was studied on nickel electrocatalysts modified with Cr, Mo, Mn, and Fe. Mass transfer limits were observed for urea oxidation at physiological concentrations (10 mmol L${\hspace{0.17em}}^{-1}$). Urea oxidation kinetics were explored at higher concentrations (200 mmol L${\hspace{0.17em}}^{-1}$), showing improved performance, but with lower currents per active site. A simplified dialysis model was developed to examine the relationship of mass transfer coefficients and extent of reaction on flowrate, composition, and pH of the reacting stream. For a nickel hydroxide catalyst operating at 1.45 V${\hspace{0.17em}}_{\text{RHE}}$, 37 ${\hspace{0.17em}}^{°}\text{C}$, and pH 7.1, the model shows a minimum geometric electrode area of 1314 cm² is needed to remove 3.75 g urea h${\hspace{0.17em}}^{-1}$ with a flow rate of 200 mL min${\hspace{0.17em}}^{-1}$ for continuous operation.