We evaluated the potential use of agri-food waste for the removal of heavy metal ions from aqueous solutions and its application in different processes (e.g., water remediation, in the production of biomass enriched in nutritionally significant elements, etc.). Biomasses from grape seed, grape pomace, loquat seed, Calabrese broccoli stem, empty pods of carob and broad bean pods, unripe bitter orange peel, kumquat, orange pulp and Canary Island banana pulp were prepared. The percentages and biosorption capacities were evaluated and compared with those refe-renced using Valencia orange peel (Citrus sinensis Valencia late). These studies allow for easily providing added value to different agri-food wastes. The results show that the proposed biomasses were able to retain the studied metal ions and obtained different percentages, being in some cases above 90%. The highest values were obtained using broad bean pod (Pb(II) (91.5%), Cd(II) (61.7%), Co(II) (40.7%) and Ni(II) (39.7%)). Similar values were observed using grape seed, broccoli stem, carob pod and unripe bitter orange peel. Carob pod for biosorption of Cd(II) is also of great interest. These studies suggest that the agri-food residues evaluated can be applied to prepare effective biosorbents of divalent metal ions from aqueous solutions.

A simple fluorescent sensor 1 has been developed for the recognition of Fe(III) in semi-aqueous solution at pH 7.0. The sensor, containing two Schiff base type receptors directly connected to naphthalene fluorophores, shows a concentration dependent decrease in emission intensity upon Fe(III) addition. The sensor was selective for Fe(III) over other metal ions and can measure Fe(III) ion concentration between 0.05 and 0.12 mM. The binding stoichiometry was established as 1:1 (host: guest) with a binding constant (Logβ) of 4.01. Furthermore, the addition of Fe(III) to a solution of 1 caused a colour change from light yellow to colourless meaning 1 is also capable of detecting Fe(III) by the naked eye.