Tunable auto-combustion preparation of TiO₂ nanostructures as efficient adsorbents for the removal of an anionic textile dye

摘要

We have developed a new route for the synthesis of pure TiO₂ nanostructures via a facile auto-combustion method followed by heat treatment. We have tuned the produced phases, morphologies, and crystallite sizes of the nano-sized TiO₂ products through an auto-combustion method employing different fuels and various fuel-to-oxidant equivalence ratios, Φ_c. The as-synthesized products were analyzed by means of FE-SEM, FT-IR, XRD, TEM, BET, and thermal analyses. Interestingly, urea fuel at Φ_c = 1 generated a pure anatase TiO₂ phase (U1) having almost the smallest crystallite size (11.9 nm) and the highest adsorption capacity (135 mg g?1) for the removal of Reactive Red 195 (RR195) dye from aqueous solutions. Moreover, the adsorption data could be described well using the pseudo-second-order kinetic and Langmuir isotherm models. Based on the calculated thermodynamic parameters: ΔH0 (1.343 kJ mol?1), ΔG0 (from ?4.630 to ?5.031 kJ mol?1), and E_a (18.46 kJ mol?1), the adsorption of RR195 dye on the as-prepared TiO₂ nano-adsorbent is an endothermic, spontaneous, and physisorption process, respectively. Moreover, the as-prepared TiO₂ adsorbent is a promising candidate for the removal of RR195 textile dye from aqueous media based on its reusability, high stability, and high adsorption capacity.