Hydrothermal synthesis of Nd-doped TiO₂ nanostructures for photocatalytic degradation of tetracycline antibiotic under visible light

The present article reveals a novel study on the synthesis of several Nd-doped nanostructured mixed-phase (brookite, rutile, and anatase) TiO₂ photocatalysts using hydrothermal and sol-gel methods. For optimization, several samples with mixed-phase TiO₂ with different Nd doping concentrations were synthesized using hydrothermal treatment by varying reaction temperature, calcination temperature, and solution pH. Out of the ten synthesized samples, the T10 (T_R ∼ 190 °C, T_C ∼ 400 °C, pH ∼ 3.6 with 2.0 mol% Nd doping) showed an excellent photocatalytic degradation efficiency (99 % within 180 min) for the removal of tetracycline antibiotics in wastewater under 100 W visible light irradiation with catalyst dose of 0.1 g/L and solution pH ∼ 6.5 and tetracycline concentration of 10 ppm. The activity of T10 is also compared to the synthesized T0 (sol-gel), undoped TiO₂ (T1, hydrothermal), P25, and single-phase anatase TiO₂ (SA, solvothermal). The T10 gives 23.8 %, 28 %, 51 %, and 78.3 % higher removal efficiency than T0, T1, SA, and P25, respectively. The unique nature of T 10 (Nd doping with mixed phase, structural, morphological, optical, chemical, and thermal properties) was examined by XRD, SEM, TEM, UV–Vis, DR spectroscopy, PL, XPS, BET, FTIR, EPR, TGA-DTA, and electrochemical analysis. The TOC and COD removal efficiency was found to be 81 % and 85 % within 4 h in the T10 sample. Moreover, a non-toxic nature was observed from a toxicity analysis. The unique degradation mechanism was also described. Cost estimation and scalability of T10 have been discussed and compared with previous works. T10 also efficiently works for photocatalytic hydrogen evolution.