Mixed oxide-polyaniline composite-coated woven cotton fabrics for the visible light catalyzed degradation of hazardous organic pollutants

Clean water and sea free of organic pollutants are among the 17 United Nation Sustainable Development Goals (SDGs). In this global concern, the design of efficient, stable and recyclable catalytic materials remains challenging. In this context, we designed a series of mixed oxide-modified cotton fabrics and their related composites and interrogated their propensity to catalyze the degradation of methyl orange (MO) (a model pollutant). More specifically, functional cotton fabrics (CF) coated with RuO₂–TiO₂ based-photocatalysts were obtained by dip-coating method at neutral pH. A layer of Polyaniline (PANI) was prepared by in situ oxidative polymerization of the aniline monomer on 4-diphenylamine diazonium salt (DPA) modified-RuO₂–TiO₂ nanoparticles (NPs) coated-CF. The modified CFs catalyzed photodegradation and mineralization of MO under visible light, which depended on polyaniline mass loading. The CF/RuO₂–TiO₂/DPA@PANI obtained by in situ polymerization was the best catalyst due to DPA adhesive layer for polyaniline to RuO₂–TiO₂, and the strong attraction force between cellulose OH groups and anilinium during polymerization. The photodegradation rate constant was 0.101, 0.0532, 0.0775 and 0.0828 min⁻¹ for RuO₂–TiO₂/DPA@PANI, RuO₂–TiO₂, RuO₂–TiO₂/PANI and RuO₂–TiO₂/DPA/PANI coated-CFs, respectively. The catalytic activity is favored by the photoactive species (OH^·,\({\mathrm{O}}_{2}^{-}\)) which are formed by the excitation of electrons under visible light but also by the electronic exchanges at the RuO₂//TiO₂, RuO₂–TiO₂//PANI and RuO₂–TiO₂/PANI//CF interfaces. CF/RuO₂–TiO₂/DPA/PANI photocatalyst was stable under simulated sunlight and reusable three times. A mechanism is proposed to account for the efficient CF catalytic properties.