Sustainable toxic dye removal and degradation from wastewater using novel chitosan-modified TiO2 and ZnO nanocomposites

Abstract

TiO2 and ZnO-embedded chitosan-based nanocomposites were prepared, immobilized on borosilicate glass, and applied for the degradation of the binary dye mixture of methylene blue and methyl orange under solar irradiation. XRD of the nanocomposites showed the existence of the anatase phase of TiO2 in the nanocomposites with crystalline sizes ranging from 13.92 nm to 17.82 nm. The FESEM results showed disintegration of the agglomerated TiO2 due to Chitosan resulting in the reduction of particle size (20.6 ± 4.6 µm to 2.9 ± 0.9 µm). BET specific surface area of TiO2/ZnO/Chitosan was 2.29 times that of pure TiO2 in addition to the reduction of bandgap energy from 3.17 eV to 2.84 eV. The photocatalytic experiment for TiO2, TiO2/Chitosan, TiO2/ZnO, and TiO2/ZnO/Chitosan showed the degradation of Methylene Blue to be 78.48%, 83.65%, 86.06%, and 91.22%, respectively and 72.53%, 80.18%, 84.3%, and 88.9%, respectively for methyl orange under solar irradiation for 5 h. The formation of heterojunction with ZnO and the enhanced adsorption capacity of Chitosan resulted in enhanced photocatalytic degradation. The reusability test of the nanocomposites showed no substantial reduction in the degradation percentage after 5 cycles of use. The reaction kinetic study suggested that the first-order model was the best-fitted kinetic model. The first order rate constant for TiO2/ZnO/Chitosan was found to be 7.88 × 10−3 min−1 and 7.10 × 10−3 min−1 for degradation MB and MO, respectively. Thus, the outcome of the experiment suggests that the application of TiO2 doped with ZnO and Chitosan results in enhanced degradation of persistent organic contaminants in textile wastewater.