Chitosan/Carbon-Doped TiO₂ Composite for Adsorption of Two Anionic Dyes in Solution and Gaseous SO₂ Capture: Experimental Modeling and Optimization

In this work, a chitosan (CHI) biopolymer was developed by loading different wt% of carbon-doped TiO₂ (C–TiO₂) with CHI to attain an efficient adsorbent of chitosan/carbon-doped TiO₂ (CHI/C–TiO₂). The fabricated materials were deployed for the removal of organic pollutants (methyl orange, MO; and reactive orange 16, RO16) and sulfur dioxide capture. The synthesized composites were characterized by BET, FTIR, XRD, TEM, SEM–EDX, pH_pzc, and pH-potentiometric titrations. Statistical modeling represented by the Box–Behnken design (BBD) was utilized for optimization of the impacts of the various parameters; A: C–TiO₂ particles loading (0–50%), B: dose (0.04–0.15 g), C: pH (4–10), and D: temperature (30–50 °C) on the adsorption of MO and RO16 dyes. The adsorption isotherms were obtained at equilibrium and under dynamic conditions, where the best fit to the isotherm results was shown by the Langmuir model and pseudo-first-order kinetic model, respectively. The maximum adsorption capacities of CHI/C–TiO₂-50 (containing 50% of C–TiO₂) was estimated at 196.6 mg/g and 270.5 mg/g for MO and RO16 dyes, respectively. This work revealed that the designed biomaterial (CHI/C–TiO₂-50) could be realized as an effective adsorbent for environmental remediation that includes decontamination of wastewater and SO₂ gas capture.