Ammonia-nitrogen removal from water with gC3N4-rGO-TiO2 Z-scheme system via photocatalytic nitrification-denitrification process.

Photocatalytic removal of NH 3 –N is expected to be an alternative to the biological method that accompanied with high energy consumption and secondary pollution. However, NH 3 –N is always oxidized into nitrate and nitrite during the photocatalytic processes, which also need to be removed from the water. Herein, the g-C 3 N 4 /rGO/TiO 2 Z-scheme photocatalytic system was prepared and used for the NH 3 –N removal. The results showed the rate constant of NH 3 –N conversion on it was 0.705 h−1, 1.7 times as high as that on g-C 3 N 4 /TiO 2 , and most of the NH 3 –N were converted into gaseous products. And the experiment result indicated NH 3 –N and NO 3 − in water could enhance the removal of each other. According to the results, the main reaction mechanism is speculated as: ·OH radicals and ·O 2 − radicals were generated on TiO 2 and oxidized the NH 3 –N into NO 3 −, and the latter was reduced into non-toxic N 2 on the conduction band of g-C 3 N 4. Finally, NH 3 –N removal performance for actual coking wastewater was investigated, and the stability of the photocatalyst was tested. This work provides some theoretical basis for the two-step degradation of pollutants by Z-scheme photocatalytic system. • NH3–N removal was realized by photocatalytic nitrification-denitrification process. • g-C3N4/rGO/TiO2 was used for treatment of actual coking wastewater. • The stability of g-C3N4/rGO/TiO2 used in actual wastewater was tested. • Interaction of NH3–N and NO3 during the photocatalytic process was investigated. [ABSTRACT FROM AUTHOR]