A recent article in Scientific Reports presents a study on polyvinyl alcohol (PVA) films embedded with biochar-modified titanium dioxide (TiO₂) nanocomposites, developed to improve water treatment performance. The materials were designed to address dye removal and disinfection challenges in wastewater management.
With growing concerns over water pollution, the researchers focused on TiO₂ for its photocatalytic properties and biochar for its adsorption capacity, aiming to create a cost-effective and efficient solution for pollutant removal.
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Background
Titanium dioxide is widely studied in water treatment due to its ability to degrade organic pollutants under UV light and adsorb contaminants such as heavy metals and dyes. However, using TiO₂ in powder form presents challenges. These include particle agglomeration, limited active surface area, and the need for post-treatment separation.
To overcome these limitations, the researchers incorporated biochar, a porous, carbon-rich material produced via biomass pyrolysis. Biochar is known for its high surface area, functional groups, and affordability. Integrating biochar with TiO₂ enhances adsorption properties and addresses the drawbacks of using TiO₂ alone. Embedding these materials in a PVA matrix provides a stable, easy-to-handle composite with potential dual functionality: pollutant removal and microbial disinfection.
Methods: Synthesis of Nanocomposites and Film Fabrication
The team synthesized titanium dioxide nanowires (TNWs) using a hydrothermal process with sodium hydroxide as the solvent. The mixture was processed at 240 °C for 72 hours in an autoclave. Separately, biochar nanorods were prepared from rice husk through pyrolysis at 400 °C under a nitrogen atmosphere.
Two composite preparation methods were explored: in-situ and ex-situ. In the ex-situ method, TNWs were first dispersed in water, and then biochar was added. The mixture was sonicated and stirred to ensure good interaction before being centrifuged, washed, and dried.
To produce the final nanocomposite films, various concentrations of TNWs and biochar-modified TNWs were dispersed in water and mixed with PVA and glycerol (as a plasticizer). The blend was heated until fully dissolved, then cast into films and dried.
Material characterization was performed using:
- TEM and SEM to examine structure and surface morphology
- FTIR to identify functional groups
- XRD to assess crystallinity
- N₂ gas sorption analysis to evaluate porosity and surface area
Results and Discussion: Performance in Dye Removal and Disinfection
TEM and SEM confirmed that the TNWs had a uniform nanowire shape, with an average diameter of approximately 45 nm. Biochar nanorods had a diameter of around 19 nm, confirmed by TEM and SEM analysis. The successful modification of TNWs with biochar contributed to enhanced surface interactions, as evidenced by FTIR spectra demonstrating significant hydrogen bonding and coordination between the functional groups of the modified materials.
Surface area analysis revealed that the pore characteristics of modified samples, particularly the nanocomposites, were significantly improved, indicating increased adsorption potential. The results showed that the specific surface area of the titanate nanowires increased considerably after modification, supporting the hypotheses that these enhancements would lead to improved performance in water treatment applications.
When tested for methylene blue removal, the modified nanocomposites demonstrated near-total removal efficiency (up to 100 %) within 20 minutes, either in powder form or as films. This rapid adsorption was validated through kinetic studies that conformed to the Langmuir model, suggesting monolayer adsorption on a surface with a finite number of identical sites, and following a pseudo-second-order kinetics, which indicates that the adsorption process is likely to involve chemical reactions rather than simple physical adsorption.
Moreover, the biochar-modified composites displayed notable antibacterial activity against pathogenic microorganisms, suggesting their dual functionality as effective adsorbents and biocidal agents.
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Conclusion
This study demonstrates the successful development of PVA-based films containing biochar-modified titanium dioxide nanocomposites, designed for efficient water purification. The materials showed high adsorption capacity, rapid dye removal, and antibacterial properties, making them practical for wastewater treatment.
The integration of biochar not only enhanced structural and surface characteristics but also contributed to the materials’ multifunctionality. Embedding the composites in a polymer matrix offers handling and processing advantages, supporting scalability and real-world application.
These findings highlight a promising direction in the development of sustainable, high-performance water treatment systems. Future research could explore large-scale production, long-term performance, and broader pollutant removal, helping address global challenges in clean water access and environmental remediation.
Journal Reference
Ghanem A.F., et al. (2025). Polyvinyl alcohol film comprising biochar modified titanium dioxide nanocomposites as decoloring and disinfectant agents. Scientific Reports 15, 11423. DOI: 10.1038/s41598-025-87432-7, https://www.nature.com/articles/s41598-025-87432-7