Lignin nanospheres loaded with titanium dioxide: A novel catalytic carrier system for achieving elevated visible light photocatalytic activity

Titanium dioxide (TiO 2 ) is a promising photocatalyst for environmental pollutant treatment. However, nano-TiO 2 particles have poorly visible light absorption capability, are susceptible to agglomeration, and experience easy electron–hole recombination. Herein, highly photocatalytically active lignin nanospheres loaded with TiO 2 (LNST) were prepared, leveraging strong visible light absorption, abundant active functional groups, and π-conjugation effects of lignin nanospheres (LNS). The results showed that the photocatalytic efficiency of LNST-4 for removing Rhodamine B (RhB) was significantly enhanced, achieving a RhB (50 mg/L) removal rate of 97.4 % under the irradiation of visible light within 120 min. The apparent rate constant was 0.043 min −1 , which was 9 and 20 times higher than that of P-TiO 2 and P25, respectively. Moreover, LNST-4 maintained good photocatalytic performance within a pH range of 3–9 and RhB concentration range of 25–100 mg/L. In the photocatalytic degradation of RhB, ·O 2 − and h + were the primary active species. The degradation pathway of RhB was proposed based on Liquid Chromatograph Mass Spectrometer (LC-MS) analysis and Density Functional Theory (DFT) theoretical calculations. Toxicity assessments revealed that photocatalytic treatment reduced the ecological toxicity of RhB. This study offers a viable strategy for enhancing the photocatalytic performance of TiO 2 while enabling the resource utilization of lignin.