EMERGENCE

Compiled by Caryn Smith, IFN Chief Content Officer

International Filtration News Explores Trending Innovation

In this new feature, IFN highlights significant research from universities and institutions around the world. If you are a part of a project you would like to highlight, email csmith@inda.org. Please write “IFN Emerging Research Submission” in your subject line in order to apply. Please send a completed press release and/or summary of the research as you would want it to be printed, a link to the university online story (if applicable), and all high resolution photographs/charts/graphs, short researcher bio(s). All selections could be edited for length.

The University Of Akron

What Do You Do With All This Plastic?

By Moni Mahesh Ghosh and Sadhan C. Jana

The global plastic waste generated annually is already in the million metric tons and the problem is ever-growing with land filling as the most popular disposal method. It is widely recognized that plastics in landfills will take hundreds of years to degrade1. Among the plastic wastes, polyolefins are most abundant due to their versatile applications and considerable chemical resistance. It is imperative to develop methods to upcycle them (i.e., to recycle this class of materials while adding commercial value to them).

The researchers in Prof. Sadhan C. Jana’s group in the School of Polymer Science and Polymer Engineering at The University of Akron have found a unique method of upcycling polyolefins from waste streams using plant-based solvents known as terpenes. The group investigated the viability of manufacturing highly porous solid structures called aerogels with polyolefins, mainly high-density polyethylene (HDPE) and isotactic polypropylene (iPP) and using them as filter media for oil-water separation and air filtration.

These aerogels are being produced by the method of thermally induced phase separation (TIPS) after dissolving the polymers in two of the more commonly available terpenes – orange terpene derived from oranges and beta pinene derived from pine trees. The properties of these aerogels depend on the solvent used, specific type of polyolefin used (HDPE/iPP), and the weight percent of the polymer in the solution.

The ongoing research focuses on fundamental understanding of the structureproperty relationships of the aerogels and their viability as filter media, either as self-standing structures, e.g., as cylindrical monoliths, or in a hybrid structural form, such as supported by 3D-printed scaffolds.

The results of the study will be communicated to a peer-reviewed journal. The aerogel specimens were manufactured from both virgin polymer pellets and from segregated polyolefinic waste with either HDPE or PP as the base polymer and with unknown additives. These aerogels were then used in oil-water separation and air filtration and their efficiencies were benchmarked against known commercial filters or materials that are used for similar separation operations, namely, surgical face masks and cellulose-polypropylene based oil absorbents. For some of the aerogel samples that were tested, the air filtration performance was at least 5% more and the oil absorptivity from an oil-in-water emulsion was at least 33% more than the corresponding commercial benchmark materials. The HDPE aerogels had considerably higher compressive strength while the iPP aerogels had considerably higher specific surface area and a higher fraction of mesopores.

It is known in melt-processing that mixed polyolefin wastes do not produce homogeneous materials due to immiscibility of polyolefins. However, the method adopted in this work leads to synergy, in that, co-existing, high-surface area polyolefin phases work in unison to fetter out airborne particles or oil phases. These aerogels can be manufactured in netshape, thereby opening the avenues for potential applications like oil spill cleanup, modular air filtration, carbon capture etc.

Moni Mahesh Ghosh is a chemical engineer by training now pursuing PhD in the School of Polymer Science and Polymer Engineering. His research focuses on the manufacture and use of various porous polymeric structures. His email is mg270@uakron.edu

Sadhan C. Jana, BF Goodrich Professor and Associate Vice President for Research and Business Engagement at the University of Akron, leads aerogel research funded by industries and federal agencies for potential applications in wounddressing, air filtration, cleaning of water, among other things. His email is janas@uakron.edu.

1. Roland Geyer et al. Production, use, and fate of all plastics ever made. Sci. Adv.3, e1700782(2017).

©Article written exclusively for the International Filtration News.

Dartmouth

A Filtration System Powered by Synthetic Molecules and Light

By Kim Martineau

Potential applications for a light-controlled pump developed by Dartmouth scientists include filtering environmental pollutants and treating cystic fibrosis.

Tiny molecular machines in humans carry out much of the work that occurs within cells, from replicating DNA to ferrying materials across the cell membrane. For decades, scientists have tried to replicate these miniaturized workhorses outside of the body, with dreams of applying them to tasks like environmental cleanup, drug delivery, and the diagnosis and treatment of disease.

But artificial molecular machines have proven easier to design on paper than to implement in real life. In a new study in Science, researchers offer a demonstration of their potential eight years after the Nobel Prize was awarded to three chemists for their work on molecular machines.

Researchers show that a synthetic receptor designed to both capture and release negatively charged ions, or anions, can move target molecules against a concentration gradient in solution, fueled only by natural light.

“This is a proof of concept that you can use a synthetic receptor to convert light energy into chemical potential for removing a contaminant from a waste source,” says the study’s senior author, Ivan Aprahamian, professor and chair of the Department of Chemistry.

The synthetic, tripod-shaped receptor that Aprahamian and his co-authors designed has two important properties. It comes in forms that can both trap and discharge negatively charged molecules. At the same time, it behaves like an electrical switch, turning on and off when exposed to different wavelengths of light. When the switch is turned on, the receptor picks up target anions. Flip the switch off, and the receptor lets the anions go.

The receptor’s unusual properties allowed researchers, to control the flow of chloride ions from a low-concentration solution, on one end of a U-shaped tube, to a high-concentration solution on the other. Over a 12-hour period, the study reports, they moved 8% of chloride ions against the concentration gradient across a membrane embedded with the synthetic receptors.

In absolute terms, the chloride ions were driven almost 1.4 inches – the width of the membrane separating both ends of the tube. Relative to the receptor’s tiny size, they covered an impressive distance, fueled by light alone.

“It’s the equivalent of kicking a soccer ball the length of 65,000 football fields,” says Aprahamian.

Aprahamian’s lab has long focused on a class of synthetic compounds known as hydrazones, which switch on and off when exposed to light. During the pandemic, PhD student Baihao Shao came up with the idea to enhance the hydrazone receptor so that it could both collect and release target anions when switched on and off.

Aprahamian tried to dissuade him. “I told him that while it is a great idea, I do not think it will be competitive with the other impressive photoswitchable receptors in the literature,” he says. “Luckily, Baihao ignored me, and he went ahead and actually designed the receptor.”

They chose chloride as their target anion for two reasons.

During winter, stormwater runoff laden with road salt raises chloride levels in waterways, causing harm to plants and animals. The transport of chloride ions also plays a key role in healthy cell functioning. The disease cystic fibrosis is caused by cells being unable to pump out excess chloride. The trapped ions cause dehydration in cells, leading to a buildup of thick mucus in the lungs, among other organs.

“As a proof of concept, we show that designing synthetic chloride pumps is achievable,” says Aprahamian.

The researchers found that their hydrazone receptor worked best on chloride, bromide, and iodide ions. But it could theoretically be modified to target other anion-rich pollutants, ranging from radioactive waste to the phosphates and nitrates in fertilizers that get washed into waterways, causing massive dead zones.

“Ideally you can have multiple receptors in the same solution, and you can activate them with different wavelengths of light,” says Aprahamian. “You can target and collect each of these anions separately.”

Not only can the receptor be controlled by a renewable source of energy – light – it is relatively easy to make and modify, he adds. Researchers created the receptor by stitching the tripod together using “click chemistry,” a Nobel Prize-winning technique that chemist Barry Sharpless ‘63 helped invent years after graduating from Dartmouth.

Molecular machines are abundant in nature, powered by ATP in animal cells, and by the sun, in plant cells. “We want to mimic such biological processes, using sunlight as the energy source to create autonomous and self-sustaining filtration systems,” says Aprahamian.

Read: https://faculty.dartmouth.edu/artsandsciences/news/2024/08/filtrationsystem-powered-synthetic-molecules-and-light