Fish scales remove fluoride from groundwater
doi:10.1038/nindia.2017.19 Published online 10 February 2017
Researchers have found that powdered fish scales can adsorb fluoride ions, making it a potentially useful technique to remove excess quantities of the mineral from groundwater1.
Beyond a certain limit, fluoride is harmful. Long-term exposure to fluoride-contaminated water is known to sometimes cause dental and skeletal deformities, as well as cancer. Existing fluoride-removing techniques work under low pH and are ineffective.
In search of a better fluoride adsorbent, scientists from the University of Burdwan, West Bengal dried and ground scales of Catla catla fish into powder. They then tested its efficiency to remove fluoride ions from solution. The percentage of fluoride removal rose with increases in adsorbent doses and pH levels of the fluoride solution.
When the contact time between the fluoride solution and the adsorbent increased, fluoride adsorption increased, reaching a maximum after an hour. However, increase in temperature reduced the adsorbent’s capacity for removing fluoride.
The powder was able to efficiently bind to fluoride ions due to presence of pores and cavities on its surface. Metal oxides and chemical groups present in the fish scales also bound to fluoride ions, helping the adsorbent remove more than 98% fluoride under slightly acidic pH.
Since fish scales are a widely-available waste material, this cheap technique could be used to treat fluoride contamination, the researchers say.
1. Bhaumik, R. et al. An optimization study for defluoridation from synthetic fluoride solution using scale of Indian major carp Catla (Catla catla): an unconventional biosorbent. J. Flu. Chem.195,57-69 (2017)