Amorphous titanium dioxide as an adsorbent for dye polluted water and its recyclability

Amorphous TiO₂, synthesized from TiCl₄ and diluted NH₃ solution, was characterized by X-ray diffraction spectrometry, UV–Vis diffused reflectance spectroscopy, Fourier-transformed infrared spectroscopy, and scanning electron microscopy. The powder exhibited high specific surface area at 508 m²/g as measured by the Brunauer-Emmett-Teller method. The pH at point of zero charge of the as-prepared amorphous TiO₂ was determined by the pH drift method to be 6.8. The product was studied for its sorption efficiency using two dyes—crystal violet (CV) and malachite green (MG). Studies on the effects of various sorption parameters (contact time, TiO₂ dosage, pH of solution, and initial concentration of dye) were carried out in order to find the optimum adsorption conditions for which the results were: contact time ~30 min, TiO₂ dosage ~0.05–0.1 g, pH 7–9, and initial concentration <1 × 10^?4 M. The adsorption data were analyzed and fitted better with the Langmuir model than the Freundlich model. The maximum adsorption capacities obtained from the Langmuir model were 0.4979 and 0.4075 mmol dye/g TiO₂ for CV and MG dye, respectively. In addition, the regeneration and the recyclability of the prepared amorphous TiO₂ were also studied. The used adsorbent should be regenerated 10–12 h before reuse in the next cycle for the best result.