A recent study published in Scientific Reports examined how nitrogen-doped titanium oxide (N-doped Ti3O5) nanoparticles can be used as photocatalysts to break down phenolic compounds in industrial wastewater. These pollutants are common byproducts of petrochemical processes and pose risks to both environmental and human health if released untreated into natural water sources.
Photocatalytic degradation is gaining interest as a method for removing these hazardous compounds. This technique uses light-activated materials to drive chemical reactions that break down pollutants. The researchers focused on N-doped Ti3O5 as a potential alternative to traditional catalysts, aiming to improve degradation efficiency under common light sources like UV, visible light, and sunlight.
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Background
Conventional wastewater treatment methods such as adsorption, chemical oxidation, and biological treatment have known limitations. These include high energy requirements, limited effectiveness, and sensitivity to environmental factors like pH. Photocatalysis offers a more sustainable alternative because it can fully break down organic pollutants into harmless products using light energy.
Titanium dioxide (TiO2) is a well-studied photocatalyst, but it has drawbacks. Its wide bandgap limits its ability to absorb visible light, and it often suffers from quick recombination of charge carriers, reducing its effectiveness.
In this study, the researchers investigated nitrogen-doped Ti3O5, a modified titanium oxide with a narrower bandgap and improved charge separation, which could make it more effective under natural lighting conditions.
The Current Study
To create the N-doped Ti3O5 photocatalyst, the team used a precipitation method. Titanium (IV) isopropoxide was dissolved in a solvent and reacted with sodium hydroxide to form a precipitate. The resulting material was treated with sonication, heating, and multiple washes using deionized water and ethanol to purify the sample.
The nanoparticles were analyzed using several techniques. X-ray diffraction (XRD) provided information about the crystal structure. Fourier-transform infrared spectroscopy (FTIR) helped identify chemical bonds, and scanning electron microscopy (SEM) was used to observe the surface morphology and confirm the elemental composition.
To test photocatalytic performance, the team used Response Surface Methodology (RSM) with a Box-Behnken design. This statistical approach helped them evaluate how variables like pH, catalyst dosage, and irradiation time affected phenol degradation. A total of 17 experiments were conducted. Phenol concentration was measured before and after treatment using a UV-Vis spectrophotometer to calculate degradation efficiency.
Results and Discussion
The results showed a significant improvement in photocatalytic activity when using N-doped Ti3O5 compared to TiO2. The N-doped material achieved maximum phenol degradation efficiencies of 99.87 % under UV light, 99.78 % under visible light, and 99.779 % under sunlight. By comparison, TiO2 performed noticeably worse under the same conditions.
Optimal degradation occurred at neutral pH (7), with a catalyst dosage of 1 g/L and an irradiation time of 30 minutes.
The improved performance of N-doped Ti3O5 was mainly due to its modified structure. Nitrogen doping reduced the material’s bandgap from 2.75 eV (in TiO2) to 2.45 eV. This allowed the catalyst to absorb more light and facilitated better separation and movement of charge carriers during the reaction.
Changes in surface charge properties due to pH also enhanced the interaction between phenolic compounds and the catalyst surface, improving the overall degradation efficiency.
Kinetic analysis followed the Langmuir-Hinshelwood model, indicating that the photocatalytic reaction was driven by surface interactions between the catalyst and the phenol molecules.
The researchers also tested how well the catalyst could be reused. The N-doped Ti3O5retained its effectiveness over multiple cycles, showing strong stability and making it a practical option for ongoing wastewater treatment.
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Conclusion
This study demonstrates that N-doped Ti3O5 is an effective photocatalyst for breaking down phenolic compounds in industrial wastewater. The nitrogen doping process improved light absorption and charge transfer, leading to higher degradation efficiencies under various light sources.
These findings highlight the potential for N-doped Ti3O5 to support more efficient and sustainable wastewater treatment processes. The optimized conditions identified in this study may serve as a foundation for future work aimed at improving semiconductor photocatalysts.
Future research could explore how degradation products form and whether this approach can be applied to other types of pollutants in environmental cleanup.
Journal Reference
Narimani M., et al. (2025). Photocatalytic performance of N-doped Ti3O5 nano-catalyst for phenolic compounds removal from industrial wastewaters. Scientific Reports 15, 10511. DOI: 10.1038/s41598-025-93414-6, https://www.nature.com/articles/s41598-025-93414-6