Water May Now Be Cleaned From Heavy Metal Using Plant Waste

NTU

Scientists just made an announcement that may be deemed as good news. They have finally created a membrane made from a waste byproduct of vegetable oil manufacturing. This has the ability to filter out heavy metals that come from contaminated water.

This happened when they came upon proteins coming from by-products of peanut or sunflower oil production. These have the ability to attract heavy metal ions with ease. The best part is that it can do its job effectively.

The study studied the process of attraction which they called adsorption. With the findings, they were able to purify the contaminated water to be able to pass international drinking standards. As for the current technologies used, these are often are energy-intensive, they require power to operate, or are highly selective during the filtering process. The best part is that their membrane can potentially be a cheap, low-power, sustainable, and scalable method that everyone will appreciate.

“Heavy metals represent a large group of water pollutants that can accumulate in the human body, causing cancer and mutagenic diseases,” said Professor Ali Miserez at Nanyang Technological University in Singapore (NTU). He added, “Our work puts heavy metal where it belongs—as a music genre and not a pollutant in drinking water.”

When producing household vegetable oils, this has the ability to make waste by-products called oilseed meals. These leftovers are rich in protein and remain after the oil has been extracted from the raw plant. The NTU-led research team used the oilseed meals from two common vegetable oils: sunflower and peanut oils. They extracted the proteins from oilseed meals and then turned them into nano-sized protein amyloid fibrils. These are proteins twisted tightly together and look like ropes. These protein fibrils are attracted to heavy metals. Once they come into contact with it, they act like a molecular sieve as they trap these heavy metal ions as soon as they go near it.


Transforming Waste to Become Water Filters

“This is the first time amyloid fibrils have been obtained from sunflower and peanut proteins,” said the paper’s first author, NTU PhD student Mr. Soon Wei Long.

The researchers were able to combine the extracted amyloid fibrils with the activated carbon. The latter is a filtration material that’s been used. They did the process to create a hybrid membrane that they tested on three of the most common heavy metal pollutants: platinum, chromium and lead.

When the contaminated water flowed through the membrane, the heavy metal ions become attracted to the surface of the amyloid fibrils and stick to it. This is what they call adsorption. The high surface-to-volume ratio of amyloid fibrils means that they can effectively adsorb large amounts of heavy metals.

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The team discovered that the membranes were able to filter as much as 99.89 percent of heavy metals. Of the three metals present and tested, the filter was most effective on lead and platinum. Chromium came after.

“The filter can be used to filter any sorts of heavy metals, and also organic pollutants like PFAS (perfluoroalkyl and polyfluoroalkyl substances), which are chemicals that have been used in a wide range of consumer and industrial products,” said Miserez. “The amyloid fibrils contain amino acid bonds that trap and sandwich heavy metal particles between them while letting water pass through.”

The researchers state that the concentration of heavy metals in contaminated water will be able to determine how much volume of water the membrane is able to filter out. A hybrid membrane made with sunflower protein amyloids needs about 35 pounds of protein (16kg) to filter drinking water from the equivalent of an Olympic-sized swimming pool and one that has been contaminated with 400 parts per billion.

“The process is readily scalable due to its simplicity and minimal use of chemical reagents, pointing towards sustainable and low-cost water treatment technologies,” said Mr. Soon. “This allows us to re-process waste streams for further applications and to fully exploit different industrial food wastes into beneficial technologies.”

Furthermore, the metals trapped in water can may also be extracted and recycled even further. After the filtration process, the membrane that was used to collect these heavy metals can be burned, allowing the metals to be left behind.

“While metals like lead or mercury are poisonous and can be safely disposed of, other metals, such as platinum, have valuable applications in creating electronics and other sensitive equipment,” said co-author Professor Raffaele Mezzenga from ETH Zurich, Switzerland.


Gleening the Precious Metals Along the Way

It is important to platinum. It’s extremely precious and costs $33,000 for 2.2 pounds (1 kg). This also just needs 70 pounds of protein (32 kg). Recovering gold, on the other hand, which is worth almost $60,000, needs just half as much.

“Considering that these proteins are obtained from industrial waste that is worth less than US$1/kg, there are large cost benefits.”

The researchers say that this comes with also another great advantage. This filtration system requires little or no energy at all. This is a far cry from other methods such as reverse osmosis because this one makes use of electricity.

“With our membrane, gravity does most or all of the work,” said Mezzenga. “This low-power filtration method can be very useful in areas where there might be limited access to electricity and power.”

The paper came out several months ago in the journal Chemical Engineering. Since it was published,  the researchers have looking into the membrane’s commercial applications with BluAct, which is a European water filtration spin-off company of ETH Zurich.

 

 

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