3D Printed ‘Hydrocyclones’ Tackling Nuisance Microplastics in Drinking Water

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A group of researchers based in China and the United States have developed 3D-printed “hydrocyclones” with the potential to remove the vast majority of harmful microplastics that end up in drinking water reservoirs.

Using metal 3D printing, engineers were able to customize their cyclone separator so that it could capture polymer particles of all shapes and sizes. Given that the device has already shown over 80% efficiency in filtering out microplastics of 20µm or larger, the team says it could soon be used to do this on a large scale and take up what is now a challenge. “major challenge” in water treatment. .

Plastic waste washed up on a beach. Image via Soren Funk, Unsplash.

A “contaminant of emerging concern”

According to the researchers, microplastics, or polymer fragments between one and five micrometers in size, are rapidly becoming a “contaminant of emerging concern” among water management agencies. Whether they are “primary” microplastics from things like skincare products, or those considered “secondary” because they come from larger objects, both have the properties to last in the environment.

As a result, these tiny plastic particles are increasingly eaten by wildlife, raising concerns that humans are therefore starting to consume them as well. Although there is currently no definitive research to prove how microplastics affect human health, some studies have warned of their potential to cause cell death and allergic reactions, hence the calls to filter them out more stronger.

Doing so, however, is another matter, as water harvesting technologies tend to be designed to remove other, better understood contaminants. While previous approaches to tackling microplastics, involving induced clumping and gravitational filtration, have been tested, the researchers point out that they are not used, due to their “low removal efficiency and cost high energy”.

The prototypes of mini-hydrocyclones printed in 3D by the researchers.  Image via Northeast Petroleum University et al.
The prototypes of mini-hydrocyclones printed in 3D by the researchers. Image via Northeast Petroleum University et al.

Bulk filter microplastics

To develop an alternative water treatment process, the team drew inspiration from hydrocyclones used in processes for separating food, chemical and plastic waste. Given their speed, cost-effectiveness, and load capacity, these devices represent a promising candidate for microplastic removal. So the team looked to build on their design by making them smaller and 3D printing them.

By fabricating a “mini-hydrocyclone” through additive manufacturing, engineers speculated that they could produce a device with stronger micro-scale capabilities and, by using stainless steel to do so, give it the ability to separate polymers of varying densities.

Putting this concept into practice, the team 3D printed two different models: one to filter out large microplastics and one for those that are broken down into smaller particles. These devices were then deployed to remove nylon and low-density polyethylene (those commonly found in untreated water) from the samples, with the concentration of each measured before and after mini-hydrocyclone treatment.

Interestingly, by serially feeding microplastics through their prototypes, the researchers found they were able to improve their chances of removing multiple polymers, without increasing the feed pressure. In doing so, the team has therefore developed a way to increase efficiency that does not require more energy to achieve, although they admit that their devices always perform better when filtering out single contaminants.

Since, by their nature, treatment plants treat water with varying impurities, engineers say that in the future, more study is needed on the impact these might have on the efficiency of their device. That being said, the team says that their mini-hydrocyclones, with a removal rate of 92% nylon and 70% polyethylene, could still be used on a large scale in the future, in waste treatment facilities. industrial and local wastewater.

“3D printing allows the design of a mini hydrocyclone (MHC) to be highly customized to meet user needs,” the team adds in their paper. “One-step and two-step MHC experiments have proven effective. CMHs have the potential to effectively remove microplastic contamination from water sources while reducing energy costs, carbon footprint and maintenance requirements.

Scientists' ultra-light freeze-dried G-PDA-BSA airgel on a Kim wipe.
A freeze-dried 3D printed water purifying airgel on a Kim wipe. Photo via University at Buffalo.

3D printing in water filtration

This is far from the first time that additive manufacturing has been deployed in water filtration applications. Late last year, researchers from FabRx, University College London and Universidade de Santiago de Compostela developed a 3D-printed drug removal device designed to separate pharmaceutical agents present in water supplies.

Elsewhere, in a similar project, a team from the University at Buffalo used 3D printing to create a water-purifying graphene airgel capable of removing dyes, metals and organic solvents from drinking water. With further development, these researchers say it may be possible to scale up their styrofoam-like material for industrial-scale deployment in large wastewater treatment facilities.

GE Research, meanwhile, received $14 million from DARPA to 3D print a wearable device that “produces water out of thin air.” While the compact system is designed to produce enough water per day to support up to 150 troops in the field, it is believed that it could also prove vital in addressing global water shortages.

The researchers’ findings are detailed in their paper titled “Separation of microplastics using mini stainless steel hydrocyclones made by additive manufacturing.”

The study was co-authored by Yian Sun, Lin Liu, Zeth Kleinmeyer, Gina Habil, Qinghai Yang, Lixin Zhao, and Diego Rosso, who hail from Northeast Petroleum University, University of California Irvine, and PetroChina Research Institute of Petroleum Exploration & Development. .

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The featured image shows a pile of discarded plastic washed up on a beach. Image via Soren Funk, Unsplash.

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