Olive Stones Remove Metals from Contaminated Waters

Olive oil consumption keeps rising as it is considered much healthier than other food oils. But the olive oil extraction leaves large amounts of agricultural residues, like olive vegetable water, browse leaves and solid waste.

A new research made by Dr. Germ�n Tenorio Rivas, a member of the research group "Solids concentration and bioremediation" from the Department of Chemical Engineering of the University of Granada (Universidad de Granada) has encountered an interesting employment for the apparently useless olive stones: they can suck up hard metals (at least chrome) through biosorption from sewage water coming from industries like painting, tannery or even the galvanizing one.

Biosorption is a physical and chemical process through which many biomass categories, like agricultural residues, can bind different ions or molecules from a solution (in this case, industrial sewage water). This method would confer a usage for the olive stones.

"We don't need to bring it from anywhere else, we already produce it here, and we produce a great amount. It is also clean and cheap", explained Tenorio Rivas, alluding to the fact that Spain is the world leader in olive oil production.

The olive stones' ability of biosorption for chrome is due to their property of binding metallic ions in their surface.

"This is due to the difference in electrical charges. Olive stones are negatively charged, whereas metal is positively charged. That is the reason why they come together, thanks to ionic attraction", Tenorio Rivas further explained.

Traditionally, these industrial waters are cleansed by precipitation, a far more complex and expensive method.

"Unlike these processes, the use of olive stones as a biosorption mechanism produces no subproducts which are then difficult to deal with, for instance, metal concentrated mud", said Tenorio Rivas.

The only byproduct of water cleansing with this procedure are the metal enriched olive stones.

"This metal can be used later".

Other approaches investigate the possibility of using olive stones to obtain fuel.