Researchers at ACS Central Science have developed a groundbreaking sugar-like polymer that effectively removes heavy metals from polluted water. This innovative polymer traps the metals in insoluble clumps, making the removal process simple and efficient. In initial tests, the polymer successfully removed ionic cadmium and lead from river water contaminated with these harmful substances.
Certain heavy metal ions can be harmful when present in high concentrations in drinking water. Traditional methods for removing these contaminants, such as filtration, can be both energy-intensive and reliant on metal-capturing membranes that clog quickly and need frequent replacement. In an effort to enhance water purification processes, researchers have turned to plants for inspiration.
Plants utilize polysaccharides—macromolecules with repeating sugar units—as a protective barrier in their cells to trap metal ions. For example, in a recent study, researchers successfully utilized polysaccharide extracts from okra and aloe to remove microplastics from wastewater.
Nonetheless, some polysaccharides dissolve in water, necessitating the addition of other substances to form insoluble gels for effective metal capture and removal. To address this challenge, Cassandra Callmann and her research team at the University of Texas at Austin endeavored to create a single material with sugar-like structures and controllable water solubility capable of efficiently removing heavy metals from water.
The research team developed a series of polymers with water-insoluble backbones and water-soluble carbohydrates attached, resembling charms on a bracelet. During testing, it was found that the carbohydrate-containing carboxylic acid group was most effective at attracting and binding ionic cadmium.
In experiments with cadmium-spiked water, this polymer formed visible clumps within three minutes, which could be easily filtered out. Furthermore, the clumps could be redissolved, releasing the cadmium by adjusting the water’s acidity. After three cycles of binding, clumping, and redissolving, the polymer maintained consistent metal-trapping efficiency, highlighting its potential as a recyclable material.
The team conducted a test on Colorado River water that was contaminated with ionic cadmium, which led to an assessment of the effectiveness of the carbohydrate-containing polymer. The river water had higher levels of ionic calcium, sodium, and magnesium compared to the added metals. After 24 hours, the polymer was able to capture 20% of the added cadmium and 45% of the added lead, while only minimal amounts of other metal ions were captured.
The researchers believe that this new material shows promise in developing more efficient, reusable, and selective materials for water purification.
Journal reference:
- Sungjin Jeon, Teron Haynie, Samuel Chung, Cassandra E. Callmann. Bioinspired, Carbohydrate-Containing Polymers Efficiently and Reversibly Sequester Heavy Metals. ACS Central Science, 2024; DOI: 10.1021/acscentsci.4c01010