Rapid microwave - Hydrothermal synthesis of CeO2 nanoparticles for simultaneous adsorption/photodegradation of organic dyes under visible light

Cerium oxide nanoparticles, synthesized by microwave mediated hydrothermal method, was characterized by using XRD, FT-IR, SEM, TEM, XPS, DR/UV-vis, and BET analyzer and applied for simultaneous adsorption/ photocatalytic decolourisation of two commonly used organic dyes namely Alizarin red S (ARS) and Eriochrome black-T (EBT). Powder XRD pattern coupled with SEM/TEM revealed the formation of single cubic phase spherical CeO2 nanoparticles with average particle size of ∼15 nm. The sample showed moderate specific surface area (47.73 m2 g−1) and relatively lower band gap (2.78 eV) than bulk CeO2. XPS study confirmed the existence of both Ce4+ and Ce3+ in the prepared sample. Batch adsorption studies without light irradiation showed significant adsorption of both the dyes on CeO2 nanoparticles with monolayer adsorption capacity (Qo) values 44.1 and 57.8 mg g−1 for ARS and EBT, respectively. Under visible light irradiation, the overall decolourisation (adsorption/photo-degradation) of both the dyes increased substantially and the optimum amount of CeO2 required for complete decolourisation of ARS (100 mg L−1) was 0.80 g L−1 while relatively lesser dose of catalyst (0.60 g L−1) was required for the same concentration of EBT. Suitable mechanisms were proposed for the decolourisation of dyes under visible light based on GC-MS/LC-MS data of the degraded products/intermediates.