The development of TiO2-biochar composite material for photodegradation of basic blue 41 and erichrome black T azo dyes from water

Abstract

This study investigates the synthesis and performance of TiO₂-biochar composite catalysts for removing Basic Blue 41 and Eriochrome Black T azo dyes, from aqueous solutions. Two types of composites were synthesized using the sol-gel method: one with pure anatase TiO₂ and biochar, and the other combining anatase-rutile TiO₂ with biochar. Biochar was incorporated at 10 %, 20 %, and 30 % weight percentages. The materials were characterized using X-ray diffraction, Raman spectroscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, surface area analysis, and ultraviolet-visible diffuse reflectance spectroscopy. The results showed that biochar significantly enhanced the surface area, increasing it from 38.0 m²/g for pure TiO₂ to 78.0 m²/g, 118.8 m²/g, and 147.1 m²/g for composites with 10 %, 20 %, and 30 % biochar, respectively. Biochar also influenced the bandgap energy, reducing it from 3.03 eV to 2.95 eV, 2.69 eV, and 2.82 eV for anatase TiO₂ composites. For anatase-rutile composites, the bandgap decreased to 2.69 eV at 10 % biochar but increased to 2.81 eV and 2.92 eV at 20 % and 30 % biochar, respectively. The composites exhibited high photodegradation efficiency, with anatase TiO₂-biochar composites achieving 98.4 % degradation for Basic Blue 41 and 97.4 % for Eriochrome Black T. The degradation followed first-order kinetics, with correlation coefficients of 0.98 and 0.99, respectively. Reusability tests showed the 20 % biochar composite retained 95.8 % efficiency for Basic Blue 41 after five cycles, while the 10 % biochar composite maintained 67.8 % efficiency for Eriochrome Black T. These findings demonstrate the potential of TiO₂-biochar composites as efficient, non-toxic, and sustainable materials for water treatment, offering an eco-friendly solution for organic pollutant removal. However, further research is needed to evaluate their performance under real-world conditions and long-term stability.