H2Ti3O7 titanate nanotubes for highly effective adsorption of basic fuchsin dye for water purification

Abstract Hydrogen titanate nanotubes with different Ti/NaOH ratios were synthesized using the hydrothermal method. The obtained materials were characterized by X-ray diffraction, UV–vis DRS spectroscopy, N2 physisorption, transmission electron microscopy and zeta potential. According to the characterization results, all the synthesized materials presented tubular morphology and the crystalline phase corresponding to H2Ti3O7. The synthesis parameters were optimized in order to increase as much as possible the specific surface area and minimize the sodium ion concentration as well. Afterward, the produced nanotubes were used as adsorbent materials to remove basic fuchsin dye from water solutions. The best adsorption performance, up to 90% in the first 5 min of testing using a load of 0.05 mgNT L−1BF, was achieved for the sample that showed the highest specific surface area (393.3 m2 g−1); the results for the other samples were around 60% under the same experimental conditions. As expected, the adsorption values were correlated to the specific surface area and point of zero charge values; in this case, at optimal pH (2.4), negatively charged NTs could capture the BF dye (pKa of 3.9) via electrostatic attraction and then ion-exchange or complexation. Through UV–vis DRS and FTIR spectroscopies, a strong interaction of the amino group in the H2Ti3O7 surface was elucidated. The results presented in this work make possible the use of this kind of materials as adsorbents of certain types of contaminants in water purification processes due to their adsorptive properties in continuous cycles.