New material perspective for waste seashells by covalent functionalization

Seashells are a calcium-carbonate-based material that can be converted into valuable advanced functional materials. Seashells are also a waste material from aquaculture. They are produced in millions of tonnes per year and represent an environmental issue. They uniquely contain an intraskeletal organic matrix rich in carboxylate groups that so far has not been exploited or has been even removed, when they were used as calcium carbonate substitutes. The intraskeletal organic matrix allows for a so far never reported covalent functionalization. Such a process strengthens the surface functionalization with respect to adsorption and, most importantly, opens up the possibility for the functionalization of the biogenic calcium carbonate with a wide variety of molecules by means of organic chemistry reactions. As a proof of concept, powdered waste oyster shells were covalently functionalized with a fluorescent probe. The impact of this research can be terrific in the valorization of CaCO3 from biogenic wastes providing advanced functional products tailored for individual applications. Moreover, its consequences on the environment and society will epitomize a perfect example of a circular economy.