Magnetic field enhanced denitrification in nitrate and ammonia contaminated water under 3D/2D Mn2O3/g-C3N4 photocatalysis

It is difficult to achieve concurrent removal of nitrate (NO 3 − -N) and ammonia (NH 4 + -N) from water thoroughly by photocatalysis due to their opposite charges and inappropriate potentials of photo-induced carriers. Herein, an innovative magnetic field enhanced 3D/2D Mn 2 O 3 /g-C 3 N 4 photocatalytic system was developed for denitrification from NO 3 − -N and NH 4 + -N contaminated water under visible light. High removal efficiency of 94.5% and 97.4% for NO 3 − -N and NH 4 + -N were achieved after imposing magnetic field. Impressively, the extra magnetic field integrated the advantages of providing driving force for NO 3 − -N and NH 4 + -N approaching catalyst surface as well as facilitating separation of photo-induced charge carriers in newly-formed II type heterojunction by generating Lorentz force . Interestingly, the electrons on conduction band of g-C 3 N 4 could reduce NO 3 − -N to NO 2 − -N, N 2 and NH 4 + -N. Subsequently, the produced NO 2 − -N could be reduced to N 2 and NH 4 + -N. Meanwhile, the holes on valence band of Mn 2 O 3 could convert NH 4 + -N to N 2 selectively, which made the dominate contribution to high N 2 recovery (93.2%) during photocatalysis. Moreover, the reusable Mn 2 O 3 /g-C 3 N 4 achieved efficient denitrification under magnetic assisted photocatalysis in real water backgrounds such as tap water and river water. This study provided an efficient and promising strategy for nitrogen remediation from water.