Tragacanth Hydrogel Integrated CeO2@rGO Nanocomposite as Reusable Photocatalysts for Organic Dye Degradation

Sunlight-driven photocatalytic degradation has attracted great attention to tackle the issue of water contaminating organic dyes. As a proof of concept, we propose that nanoceria (CeO2) decorated on the surface of reduced graphene oxide (rGO), could effectively degrade pollutant organic dyes namely methylene blue (MB) and congo red (CR), when exposed to sunlight. The formation of as-synthesized nanocomposite (CeO2@rGO) was monitored using UV-visible, Fourier transfer infrared (FTIR) and RAMAN spectroscopy, X-ray diffraction (XRD), Photoluminescence (PL), and Field emission scanning electronic microscopy (FESEM). Time-dependent dye degradation was observed for up to 5 h and followed Langmuir-Hinshelwood first-order kinetics. Notably, at equivalent concentrations (2 mg), CeO2@rGO exhibited enhanced degradation of MB (similar to 92 %) and CR (similar to 83 %) dyes when compared to bare CeO2. The photocatalytic efficiency of CeO2@rGO was further enhanced by integrating in a polymer hydrogel fabricated using tragacanth (TG), a natural gum. The hydrogel photocatalyst (CeO2@rGO-TG) exhibited similar to 91 % MB degradation, at half the amount of CeO2@rGO in free form. More importantly, CeO2@rGO-TG could be easily separated from the dye solution and re-employed for multiple cycles of degradation.