Electrocatalytic reduction of nitrate using Pd-Cu modified carbon nanotube membranes

Excessive nitrate in water is harmful to the ecological environment and human health. Electrocatalytic reduction is a promising technology for nitrate removal. Herein, a Pd-Cu modified carbon nanotube membrane was fabricated with an electrodeposition method and used to reduce nitrate in a flow-through electrochemical reactor. The optimal potential and duration for codeposition of Pd and Cu were -0.7 V and 5 min, respectively, according to linear scan voltammetry results. The membrane obtained with a Pd:Cu ratio of 1:1 exhibited a relatively high nitrate removal efficiency and N-2 selectivity. Nitrate was almost completely reduced (similar to 99 %) by the membrane at potentials lower than -1.2 V. However, -0.8 V was the optimal potential for nitrate reduction in terms of both nitrate removal efficiency and product selectivity. The nitrate removal efficiency was 56.2 %, and the N-2 selectivity was 23.8 % for the Pd:Cu=1:1 membrane operated at -0.8 V. Nitrate removal was enhanced under acidic conditions, while N-2 selectivity was decreased. The concentrations of Cl- ions and dissolved oxygen showed little effect on nitrate reduction. The mass transfer rate constant was greatly improved by 6.6 times from 1.14 x 10(-3) m/h at a membrane flux of 1 L/(m(2).h) to 8.71 x 10(-3) m/h at a membrane flux of 15 L/(m(2).h), which resulted in a significant increase in the nitrate removal rate from 13.6 to 133.5 mg/(m(2).h). These findings show that the Pd-Cu modified CNT membrane is an efficient material for nitrate reduction. (C) Higher Education Press 2023

Automated summary

In this study, a Pd-Cu modified carbon nanotube (CNT) membrane was fabricated and used for the electrocatalytic reduction of nitrate in a flow-through electrochemical reactor. The results showed that the membrane with a Pd:Cu ratio of 1:1 exhibited high nitrate removal efficiency and selectivity of nitrate reduction products at an optimal potential of -0.8 V. Nitrate removal was enhanced under acidic conditions. The mass transfer rate constant and nitrate removal rate were significantly improved by the Pd-Cu modified CNT membrane.