Electrocatalytic Reduction for Total Nitrogen Removal

Technical Principles:

Currently, researchers both domestically and internationally have conducted extensive studies on nitrate treatment technologies in water bodies, primarily focusing on physical, biological, and chemical reduction methods. Physical methods mainly include adsorption, ion exchange, membrane separation, and electrodialysis. The drawback of physical methods is that they do not completely eliminate NO₃⁻ but transfer it to another medium, concentrate, or regenerant through physicochemical processes, requiring secondary treatment. Biological methods are based on biological denitrification, where under anaerobic conditions, denitrifying bacteria utilize their own enzymes to gradually reduce NO₃⁻ to N₂ using organic carbon or inorganic salts as electron donors. However, biological methods are difficult to apply for the removal of NO₃⁻ in low C/N ratio and/or high-salinity organic wastewater, as well as in groundwater. Chemical reduction methods are based on the oxidizing nature of NO₃⁻, where reducing agents are added to the aqueous phase or in situ-generated reducing substances are used to reduce NO₃⁻. These methods primarily include reactive metal reduction, heterogeneous catalytic reduction, photochemical reduction, and electrochemical reduction. However, reactive metal reduction and heterogeneous catalytic reduction are significantly affected by water quality factors in practical applications, and complex process conditions also limit their large-scale implementation. Although photochemical reduction can achieve high treatment efficiency and N₂ selectivity, the stability of its photocatalytic system and the maturity of the process still need improvement, and it remains largely at the laboratory research stage.

Technical Advantages:

(1) No need to add chemical agents; electrons generated by the electric field on the cathode surface are directly used as electron donors for NO₃⁻ reduction, avoiding secondary pollution and additional treatment costs;

(2) The electrochemical nitrate reduction process offers high treatment efficiency, fast reaction rates, and controllable products. By optimizing electrode materials, reactors, and operational parameters, the generation of N₂ can be effectively regulated;

(3) The process is driven by electrical energy, which can be supplied by renewable sources such as solar and wind power;

(4) Electrochemical reactors have a small footprint, can be modularly assembled, and are easy to automate. They have already achieved large-scale applications in the field of advanced wastewater treatment. Therefore, electrochemical reduction for removing NO₃⁻ from water is a feasible and promising technology.

Application Areas:

● Printing and dyeing wastewater

● Pesticide wastewater

● Coking wastewater

● Pretreatment of high-COD wastewater such as biopharmaceutical wastewater;

● Advanced treatment in water treatment plants.