Polluted water is a major problem in the world, especially if it contains heavy metals. Researchers from the University of Granada collaborated with the Centre for Electrochemical Research and Technological Development, and the Centre of Engineering and Industrial Development to create a new adsorbent material to clean waters containing heavy metals and organic compounds considered pollutants from a waste material using citrus peels.

Peels from fruits such as oranges and grapefruit are abundant, but are usually thrown out because they aren’t useful. More than 35 million tonnes are produced annually in the food industry.

The new material was made with an Instant Controlled Drop treatment, a chemical treatment, which modified the structure of the peels, giving them adsorbent properties, such as greater porosity and surface area. Because of this treatment, the material is selective in order to remove metals and organic pollutants from the water.

A subsequent research by the same researchers showed that it is possible to pack the new material in fixed bed columns, similar to a filter by which wastewater runs on a constant flux process. The results show a great potential for the use of the material as adsorbents capable of competing with commercial activated carbon for the recovery of metals present in wastewater, in a way that it could be possible to carry out sustainable processes in which products with a great commercial value could be obtained from food industry residues.

Coffee grounds can also be used to filter heavy metals from water. Another use for citrus peels is making yarn out of them.

Diagram: University of Granada