Abstract:

To address the resource utilization of solid waste fly ash and the pollution of organic dyes, in this work, fly-ash-supported TiO₂ （FA/TiO₂） composites were prepared by mechanical mixing method using fly ash as carrier and commercially available TiO₂ （P25） as active center. The crystal structure, chemical composition, microstructure, elemental composition and spectral response of FA/TiO₂ composites were characterized by XRD, FT-IR, SEM, TEM, XPS and UV-vis DRS. The photocatalytic activity and stability of FA/TiO₂ composites were evaluated by using new fuchsin （NF） dye as the target pollutant. The active species and degradation mechanism were studied, and the photocatalytic mechanism was proposed. The results showed that TiO₂ （P25） was firmly anchored on the surface of spherical FA particles by Si-O-Ti chemical bond, which improved the dispersity of TiO₂ （P25） particles, as well as the UV response ability and photocatalytic activity. When the initial mass concentration of NF was 50 mg/L, the dosage of FA/TiO₂ composite was 35 mg and the initial pH was 8.0, the degradation percentage of NF by FA/TiO₂ composite reached 97.97%, which was significantly higher than that by single material. After 5 cycles, the degradation percentage of NF still reached 97.01%, indicative of excellent photocatalytic activity and stability. In presence of free radicals such as superoxide radicals （·O₂^-） and hydroxyl radicals （·OH）, NF underwent demethylation, hydroxylation and ring opening reactions and was finally degraded into small inorganic molecules.

Key words: titanium dioxide, fly ash, composite material, photocatalysis, new fuchsine