Mineralization versus photoreduction of 4-nitrophenol under the influence of surface functionalized CeO2 nanoparticles, hosted by versatile cellulose supports

Highlights: • Photocatalytic materials based on cellulose derivatives for CeO₂ NPs immobilization. • CeO₂ functionalized with silane moieties enhances the photocatalytic efficiency even under visible light. • Cellulose acetate matrix ensures high versatility, either cellulose regeneration or cellulose oxidation. • Different cellulose type matrix dictate the 4-NPh photoreaction pathway, degradation or reduction. Multiple cellulose-derived platforms were designed for the immobilization of pristine/functionalized CeO₂ nanoparticles with efficient photocatalytic activity under UV light. CeO₂ nanoparticles were synthesized at two different pH values (pH = 6 and pH = 9) observing that those prepared at basic pH have better defined shapes and, by modifying their surface with silane moieties, the band gap values decreased from 3.27 eV to 2.89 eV. The synthesized CeO₂ NPs were embedded in cellulose acetate matrix in various amounts and the achieved nanocomposites were tested as photocatalysts under UV irradiation in the photodegradation of hazardous pollutants, the optimal results being obtained at nanoparticle loading of 5 wt%. Also, the matrix type strongly influences the reaction pathway for 4–nitrophenol, from mineralization to photoreduction to 4-aminophenol. The cellulose acetate film containing functionalized CeO₂ NPs was deacetylated under alkaline medium, to regenerate the cellulose structure, and subsequently oxidized using TEMPO mediated protocol. Experiments on 4–nitrophenol photodegradation, in the presence of oxidized cellulose bearing CeO₂ NPs showed that this is completely converted to 4–aminophenol and proved the versatility of the proposed materials. Nanocomposites have good reusability results and the film containing silane-functionalized CeO₂ NPs displayed encouraging efficiency as photocatalyst under visible light.