Comparative study on the removal of different-type organic pollutants on three-dimensional hexagonal-tungsten trioxide/reduced graphene oxide nanorod arrays: adsorption and visible light photodegradation

A series of self-supporting three-dimensional (3D) hexagonal-tungsten trioxide/reduced graphene oxide (h-WO3/rGO) nanorod arrays photocatalyst are synthesized by simple hydrothermal method without substrate. By selecting cationic dye methylene blue (MB), amphoteric dye rhodamine B (RhB) and anionic dye methyl orange (MO) as model organic pollutants, the experiments indicate that the 3D h-WO3/rGO photocatalyst shows a synergistic effect of adsorption and photocatalysis under visible light irradiation for the removal of MB and RhB. WrG1 which adding 1 wt% graphene oxide (GO) during synthesis demonstrates optimal adsorption and degradation activity and the bandgap energy (Eg) of WrG1 is 2.02 eV. Adsorption removal efficiency of MB, RhB and MO are 96.0%, 62.4% and 10.9% and the total removal efficiency of MB, RhB and MO are 99.3%, 84.8% and 18.3% by 0.3 g/L WrG1, respectively. Moreover, holes (h+) were the main active species for the photocatalytic degradation of organic pollutants. This work revealed the adsorption and photocatalysis activity of three different charge dyes on the h-WO3/rGO, which facilitates in understanding the removal mechanism in combination with other analytical methods and the impact of photocatalyst chargeability on degradation of organic pollutants. The visible light bifunctional catalyst h-WO3/rGO as adsorbent and photocatalyst presents a great potential in removal cationic and amphoteric organic pollutant from wastewater without additional treatment under ambient conditions.