WHIP: A Revolutionary Water Purification System Inspired by Nature

By Muhammad OsamaReviewed by Laura ThomsonJun 24 2025

In a recent paper published in the journal npj | clean water, researchers introduced the Water Hyacinth-Inspired Purifier (WHIP), a novel water purification system inspired by the buoyancy and remediation abilities of the aquatic plant water hyacinth. This system combines photocatalytic technology with a floating, porous substrate to effectively degrade organic pollutants and nanoplastics in water.

The findings highlight WHIP’s potential to address the limitations of conventional wastewater treatment methods and offer a sustainable solution for environmental water purification.

Challenges in Water Treatment

Rapid industrialization and urbanization have significantly increased the release of synthetic dyes, heavy metals, pesticides, residues, and microplastics into water bodies. Traditional wastewater treatment methods, such as chemical coagulation and membrane filtration, often involve high costs and incomplete removal of pollutants. Photocatalysis is gaining attention as an alternative due to its stability, non-toxicity, reusability, and ability to utilize solar energy.

However, photocatalysts face challenges like particle agglomeration, difficult recovery after treatment, and poor light penetration in water. Researchers have explored the immobilization of photocatalysts on buoyant substrates to keep them at the air-water interface, thereby improving light exposure and simplifying their removal. Still, developing materials combining buoyancy, durability, and strong photocatalytic performance remains challenging.

WHIP: A New Type of Biomimetic Floating Photocatalyst

Researchers designed WHIP to mimic water hyacinth's buoyancy and pollutant-absorbing properties (Eichhornia crassipes). Their system features a hydrophobic closed-pore core that traps air for buoyancy, surrounded by a hydrophilic open-pore matrix made from polydimethylsiloxane (PDMS). The open-pore matrix is coated with titanium dioxide (TiO₂) nanoparticles, which serve as the photocatalyst. An oxygen plasma treatment enhances the matrix's superhydrophilic properties, aiding in water absorption and pollutant interaction.

Techniques such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and synchrotron X-ray micro-computed tomography (X-ray µ-CT) confirmed the interconnected pores and the presence of a TiO₂ coating. The porosity of WHIP was about 67.4%, providing a large surface area for photocatalytic activity.

The fabrication process involves drop-casting TiO₂ onto a sugar template, followed by PDMS infiltration and sugar removal to create the porous structure. The final device measures 3.3 cm × 3.3 cm × 1 cm, with a closed-pore section of 1.5 cm × 1.5 cm × 1 cm.

Performance and Stability Under Varied Conditions

The buoyancy and floating stability of WHIP were comprehensively tested. WHIP demonstrated a buoyant force of 48.2 ± 5.5 mN, nearly double that of the control TiO₂/PDMS sponge without a closed-pore core (TPS), which indicated 25.9 ± 2.3 mN. WHIP remained stable at the air-water interface under static and dynamic conditions, including a 300 rpm vortex created by a magnetic stirrer, where TPS sank quickly. After submersion, WHIP resurfaced in just 1.8 seconds from an 11 cm depth, reflecting its biomimetic design.

In photocatalytic degradation experiments, WHIP removed 38.4% of methylene blue (MB) under static conditions and 73.8% under mild stirring (150 rpm) within 180 minutes. At higher stirring speeds (300 rpm), it achieved 93.9% MB removal, outperforming TPS’s 85.1%. WHIP efficiently degraded various dyes, including 99.5% of methylene blue, 98.6% of rhodamine 6G, and 72.6% of methyl orange under ultraviolet (UV) light. Its ability to degrade nanoplastics was confirmed by a reduction in particle size from ~125 nm to ~113 nm.

WHIP also demonstrated strong reusability, retaining approximately 97% efficiency in degrading rhodamine 6G over seven cycles. For methylene blue, efficiency stayed above 90% for the first three cycles, with a slight decline later due to residual dye buildup on the catalyst, as confirmed by spectroscopic and elemental analyses.

Potential Environmental and Industrial Applications

WHIP’s design effectively addresses key challenges in water purification by combining sustainable materials, efficient photocatalysis, and a self-floating structure. Its ability to break down organic pollutants and nanoplastics under natural sunlight makes it well-suited for treating contaminated surface waters, industrial discharge, and wastewater streams.

Its floating nature allows easy deployment in natural water bodies without the need for complex infrastructure or energy-intensive mixing systems. The simple fabrication process and reusability make WHIP a cost-effective option for large-scale environmental cleanup. A scaled-up field test using a 14 cm × 14 cm WHIP embedded with a TiO₂/graphdiyne (TiO₂/GDY) photocatalyst demonstrated 94.9% methylene blue removal over three days of solar exposure, confirming its potential for real-world applications.

Advancing Future Water Treatment Technologies

WHIP is a major advancement in solar-powered water purification. It offers a low-energy solution for cleaning polluted water, supporting global environmental protection and resource sustainability goals. Unlike traditional photocatalysts, which often sink and are difficult to recover, WHIP remains afloat and harnesses sunlight to remove pollutants.

The system efficiently degrades pollutants and is highly stable by embedding photocatalysts into a porous, floating PDMS matrix with carefully designed hydrophilic and hydrophobic regions. Its ability to work with different photocatalysts, including visible-light-active materials, adds flexibility and potential for cost-effective improvements.

Future work should test new photocatalysts for improved reusability, refine the pore structure to enhance pollutant transport, and broaden their application to include more contaminants.

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