Biowaste clam shells valorisation for sustainable Hg remediation

The environmental issues linked with the huge amounts of food waste generated every year worldwide urged research aimed at converting this waste into value-added products, promoting both sustainable development and effective waste management [1-3]. The growing demand of seafood determined a rapid increase of world aquaculture, with about 18 million tons of waste shell generated annually [4]. One key environmental aspect is the management of the shells as they account for up to 75% of the weight of the mollusc. On the other hand, shells consist of calcium carbonate (95-99 wt%) and minor amounts of organic matrix [5]. In this way, shell waste represents an attractive sustainable source of Ca to produce hydroxyapatite to be used for the sustainable remediation of toxic metal polluted water. Hydroxyapatite (HAP), Ca10(PO4)6(OH)2, has been extensively researched for the remediation of waters and soils polluted by toxic metals such as Cd, Pb, Cu, Co, Ni, etc. [6,7]. However, only a few previous studies focused on the removal of Hg from water by HAP although mercury is one of the most harmful metals due to its bioaccumulation in the food chain [8]. This study investigated the capacity of clam shell-derived HAP (CSHAP) in the removal of Hg from aqueous solutions. Batch experiments were carried out at different initial Hg concentrations and contact times.