Enhanced photocatalytic degradation of dyes using a novel waste tonerbased TiO 2 /Fe 2 O 3 @nanographite nanohybrid: A sustainable approach

This study synthesized a ferric oxide - nanographite (NG) nanocomposite (Fe 2 O 3 @NG) from waste toner powder through carbonization. Subsequently, a TiO 2 /Fe 2 O 3 @NG nanohybrid was fabricated using the sol - gel technique to improve the photocatalytic degradation of dyes. TiO 2 /Fe 2 O 3 @NG nanocomposites were prepared at TiO 2 :Fe 2 O 3 @NG ratios of 2:1 (Ti:T-21), 1:1 (Ti:T-11), and 1:2 (Ti:T-12). The porosity, morphology, surface chemistry, and chemical interactions between TiO 2 , Fe 2 O 3 , and graphite in the prepared TiO 2 /Fe 2 O 3 @NG nanocomposites were characterized using the Brunauer - Emmett - Teller (BET) method and microscopic and spectroscopic analyses. The TiO 2 /Fe 2 O 3 @NG nanohybrid exhibited a reduced bandgap (2.4 - 2.9 eV) and enhanced charge carrier separation through charge transfer at the junction of the hetero-structured TiO 2 /Fe 2 O 3 @NG nanohybrid. Preliminary experiments revealed that Ti:T-21 was the most effective photocatalyst for degrading acid blue -25 (AB -25) compared to Ti:T-11, Ti:T-12, sole TiO 2 , and Fe 2 O 3 @NG. This study also investigated the impacts of catalyst dose and initial dye concentration on the AB -25 photocatalytic degradation. Notably, 97% of 5-mg/LAB-25 was removed using 1.25-g/L Ti:T21 at an unmodified pH of 6.4 within 120 min. Furthermore, Ti:T-21 exhibited remarkable recyclability in its immobilized form, achieving degradation ratios of 74.7% - 71.8% over five consecutive runs, compared to removal efficiencies of 85.0% - 62.3% in the suspended mode. Trapping experiments identified hydroxyl radicals, holes, and superoxide as the principal reactive radicals. The TiO 2 /Fe 2 O 3 @NG/light system was effective in disintegrating and mineralizing other synthetic dyes such as Congo red, methylene blue, and methyl red, indicating its potential for industrial -scale degradation of authentic dye wastewater. The utilization of waste toner for water treatment is highlighted as a strategy to promote environmental sustainability, foster a circular economy, and contribute to pollution remediation. (c) 2024 Hohai University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY -NC -ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).