Functional Coatings Improve Microplastic Removal from Wastewater

Functional polymer coatings can improve microplastic removal from wastewater by enhancing particle capture, membrane performance, and selective filtration.

Ranging from 1 µm to 5 mm, microplastics enter wastewater from both primary and secondary sources. Secondary microplastics include debris broken by mechanical abrasion, ultraviolet light, and biological degradation. For example, fishing nets degrade into smaller fibers in the ocean. In wastewater treatment plants, methods such as primary sedimentation and secondary biological treatments capture 50-90% of microplastics. Nevertheless, these processes often cannot capture small microplastics (<100 µm).

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Furthermore, microplastics bound in wastewater treatment sludge can pose environmental risks when the sludge is reused in land applications.

Functional Coatings for Microplastic Removal

Research shows that functional coatings and polymeric materials can improve microplastic removal in wastewater treatment. Some examples include:

• Hydrophilic coatings: decrease membrane fouling and increase adherence by microplastics
• Charged polymeric coatings: electrostatically attract microplastics
• Nanocellulose: hygroscopic nature and electrical charge capture and entrap microplastics

Surface engineering can improve existing treatment systems, such as disk filters and sand filters. Polymeric coatings enhance particle adhesion, control surface roughness, and promote hydrophobic or electrostatic forces. Incorporating polymeric coatings into existing infrastructure has proven effective at scale. A 2020 study in South Korea used advanced coating-assisted treatment processes to achieve over 98% removal of microplastic discharge.

Molecularly imprinted polymers (MIPs) also offer selective microplastic removal from complex wastewater matrices. These polymers act similarly to synthetic antibodies. With cavities tailored for specific microplastic shapes or chemical structures, MIPs can selectively capture target microplastics.

Advanced Treatment Methods

Recent research is advancing the capabilities of functional coatings. Hybrid technologies that integrate materials science and engineered processes offer capabilities beyond physical removal alone.

For example, artificial intelligence-enabled models aid coating design by forecasting cross-linker ratios. With minimal trial and error, researchers can optimize coating formulations for enhanced durability and adhesion. Coatings using self-healing polyurethane vitrimers with dynamic transesterification networks can repair themselves autonomously. When combined with pH-sensitive dyes or aggregation-induced emission luminogens, researchers can monitor coating integrity.

Challenges and Future Outlooks

Effective polymer coatings can decrease the amount of microplastics released into the environment after wastewater treatment. Cost, coating durability, and sustainability are just a few considerations for integrating coatings into wastewater treatment systems. At scale, pilot studies in Sweden and Singapore have shown promising results. Membrane-based systems using regenerable coatings proved to be as cost-effective as traditional methods after three to five years.