Proteins Could Help Purify Contaminated Water

Andria Chen/Staff Illustrator

Janani Ravikumar
Staff Writer

A tenacious membrane, using thin amyloid protein fibers to pull out heavy metals and radioactive wastes, could help purify water.

According to the BrightFocus Foundation, the accumulation of amyloid plaques between neurons is what sets apart a normal brain from a brain afflicted with Alzheimer’s disease. The term “amyloid” generally describes protein fragments that the body produces normally. These protein fragments are broken down and eliminated in a healthy brain, but in someone with Alzheimer’s disease, these fragments accumulate to form hard, insoluble plaques.

The new study relies on these amyloid proteins, which can filter over 99 percent of toxic materials out of severely polluted waters when paired with strong, porous carbon in a membrane. The amyloids trap lead and mercury particles, while radioactive waste particles get tangled in the membranes. Gold contaminants trapped in the membranes could later be recovered and purified; a membrane with less than six milligrams of amyloids could trap about 100 milligrams of gold.

Lenntech defines water pollution as any chemical, physical or biological change in the quality of water that has a harmful effect on any living being that drinks, uses or lives in it. Polluted water can have serious effects on health when humans consume it. There is a wide variety of different classes of water pollutants. Disease-causing agents — or bacteria, viruses, protozoa and parasitic worms — enter sewage systems and untreated waste. Oxygen-demanding wastes can deplete oxygen levels in water when there is an excess of bacteria that require oxygen.

Water-soluble inorganic pollutants, such as acids, salts and toxic metals can make water unfit to drink. Nutrients, water-soluble nitrates and phosphates cause excessive growth of algae and other water plants, which deplete the water’s oxygen supply, kill fish and make the water unsuitable to drink. Organic compounds such as oil, plastics and pesticides are harmful to humans and aquatic wildlife. Suspended sediment depletes the water’s light absorption, allowing dangerous compounds to seep through. Water-soluble radioactive compounds can cause cancer, birth defects and genetic damage.

According to the study, current technologies for purifying water are expensive and ion-specific, creating a need for more efficient and inexpensive approaches. The hybrid membranes allow the water to be filtered in such a way that the concentration of heavy metal ions drops by three to five orders of magnitude per passage. In addition, the process can be repeated numerous times and filter several ions simultaneously.

The membranes could be developed for small- or large-scale water purification units, Science News reports. The technology would only cost roughly one dollar for every 1000 liters of water filtered, and a membrane can recover hundreds of times its own value in precious metals. With a simple and flexible design, the membrane can be adjusted to optimize cleanup or metal recovery.

However, the membranes will need to be tested and optimized in real polluted waters, Science News reports. Real polluted waters may have chemical complications such as high or low acidities that could complicate the process. Still, the amyloid proteins’ contaminant-trapping capabilities could inspire other researchers to develop contaminant fibers; the amyloids’ performance has been encouraging so far.