Magnetic hybrid coagulant for rapid and efficient removal of nitrogen compounds from municipal wastewater and its mechanistic investigation

Abstract

• A novel magnetic hybrid coagulant (MHC) was synthesized. • MHC settling time was 2/3 shorter than traditional magnetic seeding coagulation. • MHC efficiently removed dissolved contaminants such as NO 3 − -N and organic nitrogen. • The NO 3 − -N removal pathways by MHC were clarified by MD simulations. • MHC was regenerated by Donnan dialysis combined with biodegradation. Dissolved contaminants (nitrate nitrogen, etc.) in municipal sewage effluent and polluted water resources need to be further removed, but common advanced water treatment technologies usually have unsatisfactory performance and large process footprints. Magnetic seeding coagulation (MSC) has a rapid settling speed; however, it is less effective for removing dissolved contaminants and cannot recover effective components. Herein, a novel covalently bound magnetic hybrid coagulant (MHC) was synthesized and used to treat secondary biological effluent. MHC settling time was 2/3 shorter than traditional MSC and showed high removal efficiencies for conventional coagulation indicators and dissolved contaminants such as nitrate nitrogen and organic nitrogen. The nitrate nitrogen removal mechanisms included nitrate nitrogen capture through the electrostatic attraction and the collision efficiency enhancement. MHC integral structure can be bioregenerated for multiple cycles. Because of its effectiveness in removing dissolved contaminants rapidly, MHC has potential application in advanced water treatment, especially in land-scarce areas.