Adsorption/photodegradation of crystal violet (basic dye) from aqueous solution by hydrothermally synthesized titanate nanotube (TNT)

Titanate nanotubes (TNTs) were synthesized hydrothermally at temperatures ranging between 150 and 160 degrees C. The synthesized nanotubes were characterised by XRD, SEM/EDX and TEM. The as-prepared nanotubes were used to remove crystal violet (CV) from the aquatic environment through adsorption/degradation and photoadsorption. All the experiments were conducted at room temperature (25 +/- 2 degrees C). The adsorption study was conducted under dark condition while the photo-degradation/photoadsorption study was carried out in the presence of UV-light (360 nm and 18 W) and adequate quantity of oxygen. The adsorption efficiency was found to be 8.361 mg CV/g TNT using Langmuir isotherm. Dimensionless parameter (R-L < 1) suggested the favourable adsorption of CV onto the TNT surfaces whereas, positive Delta G degrees (2.673 kJ/ mol) value suggested the non spontaneity of the process. Regeneration of the exhausted material with EtOH and its reuse suppressed the efficiency of the material. Adsorption followed the pseudo-second-order reaction model. Adsorption/degradation of CV in the presence of co-existing foreign ions was also evaluated. Probable adsorption/photodegradation mechanism was proposed. Finally, TNT was used to remove CV from spiked tap water and pond water with an efficiency of 75 % in each case.