Removal of Rhodamine B by g-C₃N₄/Co₃O₄/MWCNT composite stabilized in hydrogel via the synergy of adsorption and photocatalysis under visible light

Hydrogel nanocomposite as a novel porous macromolecular provides potential applications in many different fields. In this paper, Co₃O₄/g-C₃N₄/multi wall carbon nanotube (MWCNT) nanocomposites were stabilized in resorcinol formaldehyde hydrogel for a highly efficient removal of Rhodamine B from aqueous solution. Hydrogel, Co₃O₄ in hydrogel, g-C₃N₄ in hydrogel, Co₃O₄/g-C₃N₄ in hydrogel and Co₃O₄/g-C₃N₄/MWCNT in hydrogel were synthesized and characterized by Fourier-transform infrared spectroscopy (FTIR), UV–Vis diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), BET, BJH, Scanning Electron Microscope (SEM) and energy dispersive X ray (EDX). BET results showed that the presence of nanomaterials in synthesis steps of hydrogel, increase specific surface area about 22.5-30 times. DRS results confirmed that the stabilization of g-C₃N₄ and Co₃O₄ nanoparticles in hydrogel effectively shifted absorption edge to longer wavelength (red shift). The aim of this study is to eliminate Rhodamine B from solution by semiconducting materials which stabilized in hydrogel. Adsorption and synergistic performance of each sample in removal of 3 ppm solution of Rhodamine B were evaluated by UV–Vis spectrophotometry in dark and under visible light irradiation, respectively. The best removal performance (87%) was obtained by Co₃O₄/g-C₃N₄/MWCNT nanocomposites stabilized in hydrogel in 120 min under visible light irradiation. All of the samples follow first order kinetic model in removal of Rhodamine B. This study provides new insights into the stabilization of catalysts in hydrogel as a porous material and facilitates their application in the synergistic removal of dye in the field of water treatment.