Sonochemical preparation and photocatalytic application of Ag-ZnS-MWCNTs composite for the degradation of Rhodamine B under visible light: Experimental design and kinetics modeling

Composite of silver, zinc sulfide and multi-walled carbon nanotubes (Ag-ZnS-MWCNTs) was synthesized sonochemically using a direct immersion ultrasonic probe and characterization results (XRF, XRD, FE-SEM, EDX, and DRS) showed the success of composite synthesis. The photocatalytic activity of the Ag-ZnS-MWCNTs composite was tested using Rhodamine B (Rh-B) degradation under visible light irradiation. The effects of four key operational variables (Rh-B and Ag-ZnS-MWCNTs concentration, pH, and visible light exposure time) on treatment process were analyzed and optimized using Response Surface Methodology (RSM). The maximum removal efficiency of 87.53% was obtained at optimum condition (4 mg L-1 of Rh-B, 1.25 g L-1 of Ag-ZnS-MWCNTs, at pH = 9, and an irradiation time of 116 min). In continuation of our investigations, a novel kinetics model was developed based on the proposed mechanism for the photocatalytic process. Eventually, byproducts produced within the photocatalytic degradation of Rh-B dye were identified by gas chromatography-mass spectrometry (GC-MS) technique. (C) 2018 Elsevier B.V. All rights reserved.