Plant waste can filter heavy metals from water, study finds


Recently, researchers have revealed that they have developed a membrane capable of filtering heavy metals from contaminated water made from vegetable waste, in particular that resulting from the production of vegetable oil.

They found that proteins made from by-products of sunflower or peanut oil production can effectively attract heavy metal ions.

The finding suggests that contaminated water could be purified to meet international drinking standards through the attraction process known as adsorption.

Potentials of a membrane based on plant waste

The team pointed out that modern technologies consume a lot of energy, need electricity to operate, or filter information very carefully. However, their membrane has the potential to be a low-cost, scalable, durable, and low-power technique.

Professor Ali Miserez of Nanyang Technological University in Singapore explains that a large group of water pollutants known as heavy metals can build up in a person’s body and lead to cancer and other mutagenic diseases.

Waste by-products called oilseed meals are produced during the production of household vegetable oils. These are the protein-rich by-products that remain after the extraction of crude vegetable oil.

Oilseed meals from two popular vegetable oils were used by the NTU-led research team. These oils are sunflower and peanut oils. The team separated proteins from oilseed meals and converted them into protein amyloid fibrils, rope-like structures made of tightly coiled, nanometer-sized proteins. These protein fibrils serve as a molecular sieve, trapping heavy metal ions as they pass because they are attracted to the heavy metals.

From vegetable waste to filter membranes

Soon Wei Long, a doctorate. NTU student says this is the first time peanut and sunflower seed proteins have been used to produce amyloid fibrils. Soon is the first author of the article.

To create a hybrid membrane, the researchers mixed activated charcoal with the extracted amyloid fibrils. A typical filtration material is activated carbon. Chromium, platinum and lead were used as three common heavy metal pollutants on which they tested their membranes.

The heavy metal ions in the contaminated water adhere to the surface of the amyloid fibrils when the contaminated water passes through the membrane, a process also known as adsorption. Amyloid fibrils are effective in adsorbing a significant amount of heavy metals due to their high surface to volume ratio.

The group discovered that their membranes could remove up to 99.89% of heavy metals. Of the three metals tested, the filter was most effective for lead, then platinum, followed by chromium.

Miserez explained that any type of heavy metals, as well as organic pollutants like PFAS or perfluoroalkyl and polyfluoroalkyl substances, can be filtered using the filter. Chemicals known as PFAS have been found in a variety of industrial and consumer goods. Amino acid bonds in amyloid fibrils trap and sandwich heavy metal particles while letting water through.

According to the researchers, the amount of water that the membrane can filter depends on the number of heavy metals present in the contaminated water. To filter drinking water, a hybrid membrane made of sunflower protein amyloids will only need 16 kilograms of protein if an Olympic swimming pool is contaminated at 400 parts per billion.

Soon describes how the method is easily scalable due to its simplicity and low reliance on chemical reagents, highlighting the need for cost-effective and environmentally friendly water treatment methods. This allows the team to fully utilize various industrial food wastes in beneficial technologies and reprocess waste streams for additional applications.

Additionally, the trapped metals can be released and recycled again. After filtration, the metals can simply be removed by burning off the membrane that was used to trap them.

Professor Raffaele Mezzenga, co-author of the study from ETH Zurich, Switzerland, pointed out that other metals, such as platinum, have valuable applications in the creation of electronic devices and other equipment. sensitive, while metals such as lead or mercury are toxic and can be disposed of safely.

Read also: Increase in cases of water contamination – Should we preserve water for future generations?

Filtering Priceless Metals

Only 32 kg of protein is needed to recover the precious platinum, while only half that amount of protein is needed to recover the gold. Platinum is valued at $33,000 per kilo, while 1 kg of gold costs nearly $60,000.

Mezzenga noted that there are significant financial benefits given that these proteins are produced from industrial waste worth less than US$1/kg, Good News Network reports.

The fact that this filtration uses little or no energy, unlike other techniques like reverse osmosis, is another important advantage, according to the researchers.

Mezzenga went on to say that gravity does most or all of the work in their membrane. In areas where access to power and electricity may be limited, this low power filtration technique can be very useful.

The researchers have been working with BluAct, an ETH Zurich spin-off company specializing in water filtration in Europe, to investigate commercial applications of their membrane since the publication of their paper in the journal Chemical Engineering three months ago.

Related Article: Should You Use a Ceramic-Based Filter Pitcher?

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