Microplastics are ubiquitous in the environment, posing health threats to marine, freshwater and terrestrial biomes. Removal of this micropollutants from potable water sources currently relies on filtration membranes. As these systems tend to clog, a more efficient and sustainable means of eliminating microplastics from water supplies is needed. A hydrogel-based treatment technique devised at the Indian Institute of Science may prove to be an optimal solution.

A multi-layered hydrogel material consisting of chitosan, polyvinyl alcohol and polyaniline forms an interpenetrating polymer network architecture that is infused with nanoclusters of copper substitute polyoxometalate. These nanoclusters function as catalysts when exposed to ultraviolet light, resulting inMicroplastic adsorption on hydrogel and fluorescent-tagged microplastic detection via spectroscopy. Source: Soumi Dutta, Indian Institute of Science photocatalytic degradation of microplastics captured within the hydrogel structure.

This approach was tested by submerging the hydrogel material in water samples spiked with a pre-prepared microplastic powder and microplastic fragments generated by grinding waste food containers. The microplastic particles were stained with a fluorescent dye to enable their detection through fluorescence spectroscopy.

The efficacy of the hydrogel for this application was demonstrated by the removal of 93% to 95% of the two types of microplastic in the prepared water samples at a near-neutral pH. Repeated testing confirmed that the hydrogel remained effective for microplastic capture and removal for up to five treatment cycles. Once fully spent, the material could be upcycled via hydrothermal processing to form carbon quantum dots as a useful nanomaterial that can also be used to remove heavy metal contamination from water.

Physical materials testing also demonstrated that the hydrogel described in the journal Nanoscale was durable and remained stable across a wide range of temperatures.