Researchers from King Abdullah University of Science and Technology (KAUST) in Saudi Arabia are turning plastic bottle waste into molecular filters for the chemical industry.

The team of KAUST researchers is turning recycled polyethylene terephthalate (PET) into porous membranes for filtration and purification applications within the chemical industry, separating molecules from liquids. Because PET is both plentiful — produced in amounts reaching into millions of tonnes worth, according to estimates — and chemically and mechanically sturdy, the team opted to use the material as a filtering membrane.

To achieve this, the team dissolved PET and then applied another solvent to stiffen the PET again, this time in a membrane shape and not a bottle shape. The team then devised a process for forming pores within the newly shaped PET membrane using polyethylene glycol (PEG), which is an additive. Once the team established the process for forming the pores and controlling both their number and size, they demonstrated that a liquid could pass through the PET membrane, separating molecules of different sizes, with ease. During testing, the team determined that the PET membrane that performed this function best-contained pores that ranged in size from 35 to 100 nm wide and that covered up to 10% of the membrane.

Typically, it can take about 40% of the chemical industry’s energy to separate and purify chemicals using processes that are heat intensive, such as distillation and crystallization. As such, the KAUST team devised the new filter membrane in a bid to improve such energy expenditures as currently available filter membranes cannot tolerate the solvents generally used in the chemical industry.

The solution devised by the KAUST team also addresses the issue of plastic pollution in addition to solving the energy expenditure problem. Currently, plastic pollution is overwhelming the world’s landfills and seeping into its oceans and disrupting the food chain. However, efforts are underway all over the world to find alternative uses for waste plastic. For instance, a company in Africa is creating recycled plastic waste building blocks to construct schools. Meanwhile, a team from the University of Chester in the U.K. is converting unrecyclable plastic waste into electricity and green fuel.

The team continues to finetune the process, and their work is detailed in the American Chemical Society’s Applied Polymer Materials.