Integrated electrocatalytic packed-bed membrane reactor for nitrate removal

Abstract

Nitrate pollution has become a widespread problem that poses a potential risk for public health. Although electrochemical reduction can be an effective and environmentally friendly strategy for nitrate removal, obtaining non-polluting products (nitrogen) in a short hydraulic retention time via this electrocatalytic process is still challenging. This work features an efficient reactor design that integrates an electrocatalytic packed-bed reactor with a membrane. Granular activated carbon (GAC) loaded with bimetal catalysts (Pd and Cu) was used as the bed packing material (Pd-Cu/GAC). The carbon membrane loaded Pd-Cu, served as cathode, filter, and current collector. The inner core packed with the Pd-Cu/GAC material functioned as an extended three-dimensional electrocatalytic cathode and catalyst. This carbon membrane system can remove 100% nitrate with the packed-bed catalyst in Na2SO4 electrolyte, but only 79.38% without the packed-bed catalyst. The packed-bed configuration can also enhance the nitrogen (N2) selectivity from 39.66 to 78.31%, increasing the NO3– removal rate from 1.72 × 10−4 to 3.62 × 10−4 mmol min−1 cm−2, respectively. Notably, when NaOH electrolyte was used, the single-pass nitrate removal can achieve 100% with a 94.25 % N2 selectivity. These excellent performances highlight the potential to apply the integrated electrocatalytic packed-bed membrane reactor system reported here for large-scale nitrate remediation.