Lignin-derived carbon and activated carbon nanocomposites with TiO2 as enhanced photocatalysts for organic pollutant degradation

This study focused on developing a highly efficient carbon-TiO₂ photocatalyst for wastewater treatment using renewable carbon from lignin. Nanocomposites that consist of TiO₂ and carbon material are commonly utilized as photocatalysts due to their ability to combine the exceptional UV photocatalytic efficiency of TiO₂ with the added advantages of improved electron/hole separation and reduced resistance for charge transfer facilitated by carbon. The utilization of biomass waste for wastewater treatment presents an exciting challenge as it not only reduces environmental and health risks associated with industrial waste disposal but also remediates water contaminated with industrial dyes. The lignin, a renewable biomass, recovered from the waste black liquor of kraft pulp, was used as a templating agent for the sol–gel synthesis of porous TiO₂/C nanocomposites. Another type of nanocomposite, TiO₂/AC, was prepared by converting black liquor into mesoporous activated carbon (AC) using FeCl₃ under different conditions. The presence of lignin-derived carbon has enhanced the photocatalytic efficiency of TiO₂/C and TiO₂/AC in degrading RhB when exposed to UV radiation. The optimization of photocatalytic activity was achieved by adjusting the dosage of the activator (FeCl₃). Among the composites, TiO₂/C exhibited the most superior photocatalytic activity, showing a remarkable 2.85-fold enhancement compared to pure TiO₂. Additionally, it demonstrated the most minimal rate of recombination between excited electrons and holes.