Combining Electrocatalysts and Biobased Adsorbents for Sustainable Denitrification

Efficient treatment of domestic and industrial wastewater is one of the major challenges of the 21^st century. Among the inorganic pollutants, nitrogen species are significant contaminants and the management of the nitrogen cycle is one the most crucial part of wastewater purification. Herein, we report an integrated method that minimizes the amount of used chemicals, can be empowered by renewable energy, uses renewables materials for ammonia recovery and is scalable. Complete denitrification of wastewater was achieved by combining electrochemical and adsorption treatment for real wastewater samples from the Stockholm water pilot plant. 98% of nitrate was selectively converted to ammonia over abundant copper electrocatalysts in Na₂SO₄ supporting electrolyte at –0.6 V vs. RHE within three hours. The valorized nitrate in form of ammonia could be recovered by means of cheap Kraft Lignin-SiO₂ sorbents to achieve a total denitrification. The presented method is economically feasible, scalable and contributes to sustainable recycling within a circular economy.