https://doi.org/10.1007/s00339-025-08880-6
The removal of dyes from water, especially in wastewater treatment, is a critical environmental concern. This study demonstrates the efficient removal of dyes by adsorption and photocatalysis with Li-incorporated TiO2 nanotubes (Li-TNTAs) unannealed (~ 28 °C) and annealed at temperatures 250 °C and 600 °C. The annealing temperature significantly influences their structure, causing phase transitions and morphological shifts from tubular to interlocking structures, enhancing adsorption and photocatalytic performance. A dye removal of 99% in 10 min for Malachite Green dye by photocatalysis and 95.9% in 15 min by adsorption is achieved for Li-TNTA annealed at 600 °C. Kinetic and isothermal adsorption studies, along with pH effects (acidic, neutral and alkaline) in relation to the zeta potential of Li-TNTAs, are presented. Cyclic stability studies highlight the superiority of photocatalytic degradation over adsorptive removal during continuous use. For Li-TNTA annealed at 600 °C, the photocatalytic degradation efficiency remains stable over four consecutive cycles, whereas the adsorptive removal efficiency declines by 7.1% over the same number of cycles. Structural, morphological, compositional, and optical changes of Li-TNTAs, due to annealing are explored using various characterization techniques, with findings correlated to dye removal efficiency.