High efficiency removal of organic pollutant via the synergistic effect between adsorption and photocatalysis of rGO/TiO2/g-C3N4 composite aerogel

Three-dimensional (3D) rGO/TiO2/g-C3N4 composite aerogels (CTG-V, V = 1, 2, 3, 4) were synthesized via the hydrothermal method by using TiO2/g-C3N4 (CTO) and graphene oxide (GO) with a mass ratio of 1:1, 2:1, 3:1, and 4:1, respectively. The phase composition, microstructure, photo-electrical performance, the removal performance toward Rhodamine B (RhB), etc. of CTG-V were systematically investigated. The results showed that CTG-V exhibited a stable 3D structure, much higher light absorption ability, improved separation and migration efficiency of the photogenerated carriers in comparison to CTO. With the mass ratio of CTO to GO increasing, the adsorption reaction rate constants (ka) of CTG-V decreased but their photocatalytic degradation reaction rate constants (kp) increased gradually, and the adsorption-photocatalysis synergistic reaction rate constants (ks) of CTG-V which increased firstly and then decreased, were higher than their single ka values or kp values. After 60 min of adsorption-photocatalysis synergistic degradation reaction, the removal rate of RhB (200 mL, 10 mg/L) reached 92.19 % by CTG-2 (0.1 g), which exhibited the optimum removal performance. The ks value of CTG-2 (0.0273 min(-1)) calculated by pseudo-first-order linear fitting was 11.38, 2.87 and 1.94 times that of bulk g-C3N4, g-C3N4 nanosheets and TiO2/g-C3N4 composites, respectively. CTG-2 was easy to be separated and recycled from solution during the cycling experiments, and it presented excellent stability as it still removed 85.15 % of RhB molecules after five cycles of adsorption-photocatalysis synergistic reaction.