Ceria-decorated zeolite nanocomposite for synergistic adsorption and photocatalytic degradation of caffeine

The adsorption-photocatalytic degradation behaviour of emerging contaminant caffeine, an endocrine-disrupting compound was investigated. The adsorbent material zeolite with porous structure was modified by acid treatment to form a support for attachment of cerium oxide nanoparticles. The photoactive CeO2 was decorated on zeolite (Ceria/zeolite) using the surface modification approach. The physicochemical techniques used for the evaluation of a Ceria/zeolite nanocomposite were performed using XRD, FT-IR, SEM and EDS point mapping, and BET surface area analysis. The effect of caffeine removal was investigated by considering different parameters: pH (3-11), caffeine concentration (10-40 mg/L), and nanocomposite usage (250-750 mg/L). After 90 min of reaction, 68.32 +/- 1.38 % adsorption/photocatalytic activity was achieved under dark conditions. UV irradiation increased photocatalysis-mediated removal by 90.63 +/- 2.03 %. The process showed the best fit to the PFO model of adsorption kinetics with an R2 value of 0.98. The equilibrium data fitted well to the adsorption isotherm model of Langmuir isotherm, indicating monolayer adsorption. The residual toxicity evaluation revealed 75 % cell viability in the model algal strains. Furthermore, the synthesized nanocomposite photocatalyst can be reused for numerous cycles due to its high caffeine degradation and photocatalytic efficiency. Finally, utilizing HR-LCMS analysis, the probable mechanism of caffeine breakdown is elucidated.