Simultaneous adsorption-photocatalytic degradation of tetracycline by CdS/TiO2 nanosheets/graphene nanocomposites: Experimental study and modeling

Abstract

In the present study, binary nanocomposites were prepared by hydrothermal growth of titanium dioxide nanosheets (TNs) on different amounts (5, 10, and 15 mg) of monolayer graphene oxide (TNs/rGO(x)). Cadmium sulfide (CdS) nanoparticles with various Cd/Ti molar ratios (0.35, 0.70, 1.40) were impregnated on the TNs/rGO(x) samples by the hydrothermal procedure. The formation of anatase phase for TNs, reduction of graphene oxide, and synthesis of CdS nanoparticles were proved by powder x-ray diffraction (PXRD) and Raman analyses. The photoluminescence (PL) and diffuse reflectance spectroscopy (DRS) analyses showed that the simultaneous presence of rGO and CdS in the synthesized samples decreased the electron-hole recombination and extended the spectral response of TNs to the visible light region. The highest obtained percentage removal of tetracycline (TC) (as a pharmaceutical pollutant model) was 84% under 180 min of visible light irradiation in the presence of the CdS-TNs/rGO(5) sample. Active species scavenging tests showed that O2•- was major active species in the removal process. In addition, the application of artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS) in modeling the removal of tetracycline (TC) was evaluated in this study. The experimental results confirmed that the integration between adsorption and photocatalysis processes leads to a significant impact on the removal of TC.