Bifunctional TiO2 – cellulose based nanocomposites for synergistic adsorptive-photocatalytic removal of methyl orange: Response modelling and optimization

Removal of azo dyes from aquatic environments represents a global challenge. Herein, by utilizing the waste of mandarin peels as a cellulose source (MP500), a bifunctional adsorbent-photocatalyst, TiO₂@MP500, has been prepared via a one-pot hydrothermal synthesis. Taking advantage of this dual role, remediation of methyl orange (MO) has been successfully addressed. Characterization tools corroborated the anchoring of TiO₂ and the successful synthesis of TiO₂@MP500. SEM/EDX/TEM analyses confirmed the formation of TiO₂ nanoparticles on the carbonaceous surface. A substantial increase in the BET surface area following TiO₂ impregnation was perceived (184.61 m²/g in the case of 3 %TiO₂@MP500). Similarly, the thermal stability of the developed composite was notably improved as reflected by the thermogravimetric analysis. XRD analysis corroborated the existence of carbonaceous layer with anatase phase TiO₂. Optimization of the adsorbent-photocatalyst performance was approached using the Box-Behnken design. Five factors were premeditated, pH of the MO solution, adsorbent dose, reaction time, the concentration of TiO₂, and [MO]. A maximum sorption capacity of 104.2 mg/g was reckoned, with a pseudo-second-order isotherm. Furthermore, the 3 %TiO₂@MP500 achieved a decolorization efficiency of 98.87 % in ∼30 min. The 3 %TiO₂@MP500 nanocomposite was effectively revived and could be exploited for 6 cycles, bolstering a decolorization efficiency of 90.91 %.