“These results signify that our system could efficiently break down commercial samples of polystyrene, even with additional composite and insoluble material."Erin Stache, Cornell University

Chemists at Cornell University have discovered a way to use light and oxygen, in conjunction with iron(III) chloride as a catalyst, to upcycle the common plastic polystyrene, used to produce everything from egg cartons to compact disc cases, into benzoic acid. In addition to being stocked in undergraduate and high school chemistry labs, benzoic acid is also used in fragrances, food preservatives and other ubiquitous products.

A team led by Erin Stache, assistant professor of chemistry and chemical biology at Cornell University, found that this upcycling reaction can even take place in a sunny window. The chemists report their work in a paper in the Journal of the American Chemical Society.

In line with the Stache lab’s mission to tackle environmental concerns through chemistry, the new process is mild, climate-friendly and scalable to commercial waste streams. Moreover, the process is tolerant of the additives commonly found in a flow of consumer waste, including dirt, dyes and other types of plastics.

Last summer, Stache’s lab ran some degradation experiments in a sunny window. In a place with strong year-round sunlight, the reaction could be done outdoors.

“The advantage of using light is you can get exquisite control over the chemical process based on some of the catalysts we’ve developed to harness the white light. If we can use sunlight to drive the process, that’s a win-win,” Stache said, noting that existing polymer recycling processes require heat for melting and processing.

To test the tolerance of the catalytic process to other materials that can mixed with the polystyrene, the researchers tried it out on several products, ranging from packaging materials to coffee cup lids. They found that three items – a white coffee cup lid, Styrofoam and a clear lid – degraded efficiently. A black coffee cup lid degraded less efficiently, possibly because the black dyes inhibit light penetration.

“These results signify that our system could efficiently break down commercial samples of polystyrene, even with additional composite and insoluble material,” Stache said.

To demonstrate scalability and potential commercial application, Stache and her colleagues created a setup with two syringe pumps and two LED lamps in a 3D-printed photoreactor. The efficiency of the breakdown process at the large scale was similar to that in small batches.

“If we can make the process even more efficient, we can think about how to commercialize it and use it to address waste streams,” she said.

This story is adapted from material from Cornell University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.