3D-printed filters made from recycled nylon and titanium dioxide show promise in treating greywater efficiently, though hurdles remain before they can meet drinking water standards.
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A team of researchers has developed a novel water filtration system that combines nanotechnology with 3D printing, aiming to create a low-cost, sustainable solution for greywater treatment. As reported in Micro & Nano Letters, the study demonstrates this with a honeycomb-structured filter made from 3D-printed recycled nylon, coated with titanium dioxide (TiO2) nanoparticles.
Nanomaterials such as TiO2 are often studied in water treatment for their photocatalytic and antimicrobial properties, as well as their large surface area. These characteristics enable them to degrade organic pollutants and neutralize pathogens effectively.
However, it can be difficult to integrate such materials into practical, long-lasting filtration systems. Traditional membranes often suffer from fouling, limited operational lifespan, and high manufacturing costs.
To address this, the researchers used fused filament fabrication (FFF), a 3D printing technique that allows precise control over filter geometry. This approach enables the design of customizable, reusable filtration units that capitalize on the benefits of nanomaterials while improving mechanical stability and ease of production.
Fabricating the Filters
The team used FFF to print honeycomb-shaped modules from recycled nylon filament, and then applied the TiO2 nanoparticles via spin-coating.
This method was chosen to improve clogging behaviour and increase contaminant retention. The honeycomb design was intended to create a tortuous flow path, improving filtration through both dead-end and depth filtration modes.
Once fabricated, the filters were subjected to mechanical testing, porosity analysis, and nanomaterial distribution checks. Their performance was then assessed by passing greywater through the filters in dead-end and depth filtration modes.
Key metrics evaluated included turbidity, total suspended solids (TSS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), and microbial removal efficiency. Although the photocatalytic potential of TiO2 was factored into the analysis, it wasn’t extensively tested under real-world lighting conditions.
The study also examined filter fouling across cycles, overall stability, and possible regeneration techniques, focusing on how nanomaterial integration affects performance and durability over time.
Performance And Limitations
The nanocomposite filters showed significant improvements in removing organic contaminants and inactivating microbes compared to plain nylon filters. This enhancement was largely attributed to TiO2’s photocatalytic activity, which helps break down organic compounds and generate reactive oxygen species capable of degrading biofilms.
In initial cycles, the coated filter achieved removal rates of up to 85 % for BOD and 80 % for COD in dead-end mode. Depth filtration yielded slightly lower removal efficiencies of 80 % BOD and 75 % COD. After five filtration cycles, these figures dropped to 58 % for BOD and 50 % for COD, indicating sustained, though diminishing, performance over time.
Importantly, the addition of TiO2 did not compromise the mechanical strength of the nylon filters, which retained structural integrity across multiple filtration cycles. The filters also exhibited increased resistance to fouling, which is a common issue in membrane systems, thanks to self-cleaning TiO2.
Despite this, the system struggled to reduce turbidity and TSS to levels required for potable water. Larger particles often passed through due to the relatively large pore size and open-cell architecture of the honeycomb design, which favours flow efficiency over fine particulate capture.
The findings suggest that further refinement is needed, such as finer pore structures or a multilayer filtration approach, to improve filtration precision and consistency.
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Future Directions
The study demonstrates the impressive performance when combining nanomaterials with 3D printing for filtration systems, especially in decentralized or resource-limited settings. The integration of TiO2 not only boosts contaminant removal but also enhances the filter’s durability and reusability.
Yet, to fully meet potable water standards, further optimization is still needed. This includes refining the filters to improve their long-term performance under real-world conditions.
The research indicates the future of nanotechnology in water treatment, with practical applications in regions where traditional infrastructure may be lacking. Continued investigation into nanocomposite materials and scalable fabrication techniques will be key to turning these lab-scale innovations into everyday applications.
Journal Reference
Saha S. K., et al. (2025). Fused filament fabrication of recycled nylon‐TiO₂ honeycomb filters for greywater treatment. Micro & Nano Letters, 1–18. DOI: 10.1002/mna2.70009, https://ietresearch.onlinelibrary.wiley.com/doi/10.1049/mna2.70009