In-situ formation and entrapment of Ag/AgCl photocatalyst inside cross-linked carboxymethyl cellulose beads: A novel photoactive hydrogel for visible-light-induced photocatalysis

In this work, a novel photoactive cellulose-based hydrogel was prepared by simultaneous AgCl formation and entrapment inside Al (III) and Fe (III) cross-linked carboxymethyl cellulose beads. Physio-chemical and optical properties of the synthesized composites were well characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, elemental mapping, Fourier transform infrared (FTIR) spectroscopy, photoluminescence (PL), and diffuse reflectance spectroscopy (DRS). The photocatalytic activity of hydrogels was evaluated by the degradation of rhodamine B (RhB), as a model environmental pollutant. A comparative study showed that different cross-linkers resulted in different AgCl content, optical properties, and photocatalytic performance of hydrogel beads. Ag/AgCl@Al-CMC and AgCl@Fe-CMC composites exhibited remarkable photocatalytic performance (98 % and 87 % removal efficiency within 60 min, respectively) under visible light irradiation, and the effect of operational factors contributing to the photocatalytic process, including catalyst dosage, dye concentration, and initial pH was investigated. Scavenging experiments indicated that photo-induced hole and hydroxyl radical made a significant contribution to the degradation of RhB, and a plausible reaction pathway for the generation of major active species was proposed, according to the calculated band edge potentials of the photocatalysts. Reusability experiments revealed that the decolorization performance of the photoactive beads decreased after five repetitive experiments. This decline was attributed to the partial photocatalyst leaching from CMC polymeric network into the aqueous environment, evidenced by the results of ICP-OES analysis. The present study opens a new avenue for the development of hydrogel-based photoactive materials.