Environment

Plastic bottles could be recycled into chemical filters

Plastic bottles could be recyc...
Ola Habboud (left), Suzana Nunes and Bruno Pulido discuss their PET membrane technology
Ola Habboud (left), Suzana Nunes and Bruno Pulido discuss their PET membrane technology
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Ola Habboud (left), Suzana Nunes and Bruno Pulido discuss their PET membrane technology
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Ola Habboud (left), Suzana Nunes and Bruno Pulido discuss their PET membrane technology

In the chemical-production industry, energy-intensive processes are constantly being used to remove unwanted molecules from liquids. It now looks like much of that energy could be saved, however, by utilizing filters made from discarded plastic bottles.

According to Saudi Arabia's King Abdullah University of Science & Technology (KAUST), approximately 40 percent of the energy consumed in chemical plants is utilized in purification processes such as distillation and crystallization. Conventional filtration membranes typically can't be used instead, as they get degraded by the harsh solvents that are often present. Tougher ceramic membranes are one alternative, although they tend to be quite expensive.

With these limitations in mind, KAUST scientists looked to the polyethylene terephthalate (PET) plastic that is frequently used in the production of items such as single-use water bottles. Unlike the materials which existing low-cost filtration membranes are made of, PET is "mechanically and chemically robust," allowing it to withstand exposure to harsh compounds.

The researchers started by dissolving PET obtained from bottles, then using a solvent to make it solid again – but this time in the form of flat membranes. Over a series of trials, a polymer known as polyethylene glycol (PEG) was added to the PET in various concentrations, forming pores of differing sizes and numbers within those membranes.

It was ultimately found that when it came to removing molecules from liquids, the best-performing PET membranes had pores ranging from 35 to 100 nanometers in diameter, covering up to 10 percent of the total membrane area. The team now hopes that the technology could be adapted for large-scale use.

A paper on the research was recently published in the journal Applied Polymer Materials.

Source: KAUST

6 comments
Aross
This all sounds good for existing plastic but if we really want to solve the problem lets get rid of all plastics, stop producing it, for everything where a more environmentally replacement is available. Like glass for bottles, paper liners and containers for food products like cookies, butcher's paper for meat and fish etc. These things were good enough in the past but were replaced by plastics because it was cheaper and meant more profit for the manufacturers. As an example. when milk went from glass to plastic bags a whole new industry sprung up making the containers to hold the bags. In my 70+ years on the planet I have seen a lot of good changes and innovations but plastics was not one of them. It may have some uses but generally speaking it just replaced something that was already good for its purpose.
Ichabod Ebenezer
Generally, I agree with you Aross, but glass bottle were replaced with plastic, not because it was cheaper, but because glass breaks easily and creates a hazard. But we now have organic-based plastics that are biodegradable and are almost identical to the petroleum-based equivalent. There is no reason not to switch to those, and if it costs a few extra cents to produce, I'm willing to pay that.
buzzclick
@Aross - Your concern for plastics makes sense, but please understand that it's not so much the plastic itself that's the problem. It's the excessive use of it. Plastic is an incredibly practical material and is found in our clothing, the interior and exterior of our homes, cars, tools, equipment, computers and more....and of course in packaging. We are addicted to it (thanks to its promotion by the corporations) and use it far too much in our daily lives. The push to use plastic is not compensated by a viable way to recycle/dispose of it by the very companies who use it in their products. Governments have to set rules so that these corporations make it as easy as possible to separate all the different polymers for the recycling process to work effectively and efficiently. Using paper is fine, but we already cut down enough forests to produce magazines, office and toilet paper. Note to New Atlas team: please make this window that we leave our comments in a little bit larger. It's annoying to scroll for any possible typos. I understand if it is your wish to discourage long posts. Just a little bit bigger would be nice.
Trylon
@Ichabod Ebenezer You're operating under a couple of misconceptions. All hydrocarbon-based polymers including PET are "organic," if you remember your organic chemistry from high school. And the so-called degradable bioplastics really don't degrade much faster in the environment.
Trylon
@Aross Your cynical view of plastics belies the disadvantages of the products you favor. Butcher paper won't preserve meat for more than a day or so. Great if you actually buy fresh meat every day from a butcher, not so good if you only shop every few days, not to mention many if not most supermarkets don't have a butcher anymore. Paper liners don't keep products fresh for very long, especially ones like potato chips that need to be packaged with an oxygen barrier. Glass bottles are breakable and also quite heavy, meaning they take more fuel to transport to stores. They also don't protect against UV, which degrades taste and nutrition in products like milk.
Trylon
@buzzclick If you really need a larger text area, just drag the handle in the lower right hand corner to make it bigger.