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

Abstract

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, Φc. The as-synthesized products were analyzed by means of FE-SEM, FT-IR, XRD, TEM, BET, and thermal analyses. Interestingly, urea fuel at Φc = 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 Ea (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.