Self-purifying chloride-mediated sequential nitrate reduction-oxidation enabled by a Co-oxygen vacancy tandem...

Area of Science:

• Environmental Science
• Materials Science
• Electrochemistry

Background:

• Industrial high-salinity nitrate wastewater poses treatment challenges, especially at low concentrations.
• Conventional biological methods are inefficient for treating such wastewaters.

Purpose of the Study:

• To develop an efficient photoelectrocatalyst for deep nitrate removal from high-salinity wastewater.
• To investigate the synergistic effects of oxygen vacancies and cobalt sites in the catalytic process.

Main Methods:

• Fabrication of a tandem Co-OV/TiO2@TP photoelectrocatalyst on a titanium substrate.
• Utilizing Density Functional Theory (DFT) calculations and in situ characterization.
• Employing photoelectrocatalysis under visible light irradiation.

Main Results:

• The catalyst achieved 98% nitrate-N removal efficiency and nearly 100% N2 selectivity.
• Oxygen vacancies facilitated nitrate adsorption, while cobalt sites promoted water dissociation for reduction.
• In situ generated hypochlorite oxidized ammonium to nitrogen gas, enabling complete removal.
• The catalyst showed a 67% enhancement over the oxygen vacancy-only catalyst.

Conclusions:

• The Co-OV/TiO2@TP photoelectrocatalyst offers an efficient strategy for deep nitrate removal from industrial wastewater.
• The catalyst exhibits excellent chloride tolerance, pH adaptability, and long-term stability.
• This approach provides a promising solution for self-purifying industrial wastewater treatment.