Different TiO₂ Phases (Degussa/Anatase) Modified Cross-Linked Chitosan Composite for the Removal of Reactive Red 4 Dye: Box–Behnken Design

The present work targets to develop the cross-linked chitosan composite with different TiO₂ phases (Degussa/Anatase) to attain two adsorbents namely cross-linked chitosan-epichlorohydrin/TiO₂-Degussa (CS-ECH/TiO₂-D) and cross-linked chitosan-epichlorohydrin/TiO₂-Anatase (CS-ECH/TiO₂-A). The physicochemical characteristics including crystalline nature, specific surface area, functional groups, surface morphology, and thermal stability of the prepared composites were identified by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Fourier transform infrared (FTIR), scanning electron microscope (SEM), and thermogravimetric and derivative thermogravimetric analyses (TGA-DTG), respectively. Response surface methodology combined with Box–Behnken design (RSM-BBD) was used to explore multivariate modeling and optimization of reactive red 4 (RR4) dye removal on CS-ECH/TiO₂-D and CS-ECH/TiO₂-A based on the related factors including A: adsorbent dose (0.5–1.5 g/100 mL), B: pH (4–10), and C: time (30–90 min). RR4 dye removal was 94.6 and 87.5% for CS-ECH/TiO₂-D and CS-ECH/TiO₂-A, respectively. The adsorption of RR4 molecules on the surface of CS-ECH/TiO₂-(D/A) was constructed by many interactions e.g. electrostatic forces, n−π stacking, and H-bonding. The findings revealed that the biomaterials developed could be viable and convenient potential adsorbents for capturing azo dyes from polluted effluents.