Milking the potential of proteins

Field studies in Peru have shown that membranes made using milk proteins can remove enough arsenic from tap water to bring it within recommended safety limits for drinking. Not only that, the technology is cheap and has minimal energy requirements. 

Arsenic contamination is a serious problem in Peru. In some areas, the amount of arsenic found in groundwater has led to its concentration in drinking water exceeding safe levels set by the World Health Organisation by a factor of 100. The presence of arsenic in the hair and nails of people living in these areas shows that they have been exposed to the toxin for several decades, increasing their risk of developing various cancers and other diseases.

Scientists from ETH Zurich, Switzerland, developed a filtration system using activated carbon and milk protein fibres. They used heat and a low pH to convert whey, the main protein found in milk and a byproduct of the cheese-making industry, into nanofibrils. Amino acids on the surface of the whey nanofibrils are available to bind metal ions, including arsenic.

Now the scientists have tested their water filter system in a variety of real-life scenarios inlcuding household units and community-based units. Analysis of the water after treatment showed that 99.9% of the arsenic had been removed.

Current methods for water treatment use reverse osmosis, exchange resins or ultrafiltration, but these are technical systems that are inappropriate for moderate-income countries such as Peru. No energy is required with the new system since the technology can simply work on gravity-induced filtration of water, as opposed to the energy-intensive requirements of reverse osmosis.

Read the full story in Chemistry World.