Graphene nanosheets made from a brown seaweed biomass can remove excess fluoride from contaminated drinking water. These nanosheets are non-toxic and can be used to make water safe1.
Long-term exposure to fluoridated drinking water can cause deformation of bones and teeth. Existing techniques for removing fluoride are expensive and complex.
Scientists from the Gujarat-based CSIR-Central Salt & Marine Chemicals Research Institute and The M.S. University of Baroda and University of Rajasthan synthesized graphene by treating solid granules of the seaweed with solvents made of an organic compound and metal salts.
Iron and tin in metal salts modified the graphene, which had sheet-like structures with interconnected networks of nanopores. When dipped in a fluoride-contaminated solution, the graphene efficiently adsorbed fluoride ions, with adsorption rate increasing with time and becoming constant after two hours.
The iron-modified graphene showed the highest efficiency to remove fluoride from solution. Presence of iron makes it easy to separate the graphene from the solution using an external magnet and reuse it. The graphene removed more than 80% of fluoride ions at acidic pH from a drinking water sample.
Besides fluoride, it was able to remove toxic heavy elements such as mercury and manganese that are usually found in contaminated drinking water.
“Since the graphene is non-toxic to lung cancer cells, it is safe to use to purify fluoride-contaminated drinking water,” says lead researcher Kamalesh Prasad.