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 %.