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<p>Industrial development faces severe pollution challenges, particularly in treating refractory dyeing wastewater. Photocatalytic technology offers a promising solution due to its stability, efficiency, and environmental benefits. Compared to traditional biochemical methods, nano-TiO<sub>2</sub> enables more complete organic degradation. This study synthesized La-N co-doped TiO<sub>2</sub> (La-N/TiO<sub>2</sub>) and multi-walled carbon nanotube-supported composites (La-N/TiO<sub>2</sub>/MWCNTs) via sol-gel processing. X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), photoluminescence (PL) spectra and Brunauer-Emmett-Teller (BET) characterization confirmed anatase phase retention in all doped catalysts. Co-doping reduced TiO<sub>2</sub> crystallite size and induced a 2.64 eV bandgap red shift. Critically, XPS analysis confirmed atomic-scale bonding via distinct binding energies: N 1 s at 399.6 eV (O-Ti-N) and O 1 s at 529.8 eV (Ti-O-La), verifying dopant lattice incorporation. MWCNT incorporation enhanced specific surface area and formed composite encapsulation. Under optimized conditions (xenon lamp, 180 min; calcination 500 °C, 3 h; 1.5%La-3%N; 15 cm light intensity; pH 8; 0.8 g/L dosage; 25 °C), La-N/TiO<sub>2</sub> achieved 66.73% RhB degradation and 62.80% COD removal. The La-N/TiO<sub>2</sub>/MWCNTs adsorption-photocatalysis synergy significantly outperformed this, attaining 98.53% RhB removal and 87.80% COD reduction within 180 min. Systematic scavenger experiments confirmed that hydroxyl radicals (·OH) and superoxide anions (·O<sub>2</sub><sup>-</sup>) serve as the dominant active species in the degradation process, with contributions significantly exceeding those of direct photogenerated hole (h<sup>+</sup>) and electron (e<sup>-</sup>) oxidation. Degradation product analysis identified a pathway involving sequential N-deethylation/decarboxylation, chromophore cleavage, and aromatic ring opening, culminating in complete mineralization. Multidimensional toxicity assessment confirmed progressive detoxification, with final intermediates showing “Not Harmful” acute toxicity, reduced developmental toxicity, and no mutagenicity. This work provides new insights into practical applications of adsorption-coupled photocatalysis for RhB elimination.</p><p></p>

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Study on the synthesis of multi-walled carbon nanotube-supported La-N Co-Doped TiO2 and its coupled photocatalytic degradation of rhodamine B (RhB)

  • 期刊论文

  • 发表日期：

    2026年1月3日

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  • Zhihua Wang,
  • Bing Wang,
  • Lijian Zhang,
  • Jiyuan Li

摘要

Industrial development faces severe pollution challenges, particularly in treating refractory dyeing wastewater. Photocatalytic technology offers a promising solution due to its stability, efficiency, and environmental benefits. Compared to traditional biochemical methods, nano-TiO2 enables more complete organic degradation. This study synthesized La-N co-doped TiO2 (La-N/TiO2) and multi-walled carbon nanotube-supported composites (La-N/TiO2/MWCNTs) via sol-gel processing. X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), photoluminescence (PL) spectra and Brunauer-Emmett-Teller (BET) characterization confirmed anatase phase retention in all doped catalysts. Co-doping reduced TiO2 crystallite size and induced a 2.64 eV bandgap red shift. Critically, XPS analysis confirmed atomic-scale bonding via distinct binding energies: N 1 s at 399.6 eV (O-Ti-N) and O 1 s at 529.8 eV (Ti-O-La), verifying dopant lattice incorporation. MWCNT incorporation enhanced specific surface area and formed composite encapsulation. Under optimized conditions (xenon lamp, 180 min; calcination 500 °C, 3 h; 1.5%La-3%N; 15 cm light intensity; pH 8; 0.8 g/L dosage; 25 °C), La-N/TiO2 achieved 66.73% RhB degradation and 62.80% COD removal. The La-N/TiO2/MWCNTs adsorption-photocatalysis synergy significantly outperformed this, attaining 98.53% RhB removal and 87.80% COD reduction within 180 min. Systematic scavenger experiments confirmed that hydroxyl radicals (·OH) and superoxide anions (·O2-) serve as the dominant active species in the degradation process, with contributions significantly exceeding those of direct photogenerated hole (h+) and electron (e-) oxidation. Degradation product analysis identified a pathway involving sequential N-deethylation/decarboxylation, chromophore cleavage, and aromatic ring opening, culminating in complete mineralization. Multidimensional toxicity assessment confirmed progressive detoxification, with final intermediates showing “Not Harmful” acute toxicity, reduced developmental toxicity, and no mutagenicity. This work provides new insights into practical applications of adsorption-coupled photocatalysis for RhB elimination.