Removal of Au 3+ and Ag + from aqueous media with magnetic nanoparticles functionalized with squaramide derivatives.

New magnetic hybrid nanoparticles of Fe 3 O 4 coated with organosulfur-squaramide compounds are prepared. The modified-nanoparticles show a good coordination for Ag + and Hg 2+ cations in water, and present a high affinity for Au 3+ ions. The behaviour of the squaramide-coated nanoparticles differs significantly from that previously reported for nanoparticles used as Au 3+ scavengers. In the presence of organosulfur-squaramide, the Au 3+ salt is reduced to gold nanoparticles that are deposited upon Fe 3 O 4 nanoparticles. For the first time, the coordination capacity of the carbonyl squaramide groups with the gold cation, based on purely electrostatic cation-dipole interactions, is proved.