Preparation of Fe3O4/TiO2-N-GO sonocatalyst and using for humic acid removal with the assist of ultrasound

Abstract

Abstract In order to remove the humic acid (HA) from the drinking water efficiently, novel quaternary Fe3O4/TiO2–N-GO (FTNG) sonocatalysts with different amounts of Fe3O4 were simply synthesized, and a sono-photocatalytic system was used by combining photocatalysis and ultrasound processes. A series of characterizations were performed to confirm the successful synthesis of FTNG and some of its properties, and the results showed that FTNG with an appropriate amount of Fe3O4 can extend the range of light absorption to over 400nm (UV-vis spectra) and improve the separation efficiency of electrons and holes (Photocurrent responses). Raman spectra indicated the reduction of GO. Sono-photocatalytic performance was investigated under visible light irradiation and the effect of ultrasound was studied. Among all the catalysts, FTNG-0.2 with 0.2\u202fg Fe3O4, exhibited the best HA removal abilities, about 80% for sono-adsorption and 93% for sono-photocatalysis. The removal efficiency in sono-photocatalytic system was about 42% higher than only adsorption and 26% higher than only photocatalysis. Finally, we proposed the possible reaction mechanisms. First, ultrasound pretreatment had a positive effect on HA removal, and a Fenton-like system was then established with H2O2 produced by cavitation effect. Second, the doping of Fe3O4, N and GO improved the quantum efficiency. The improvement of visible light catalytic performance is mainly attributed to the doping of N. This work is significant for the field of ultrasonic and catalytic degradation, especially for the removal of humic acid in drinking water.