Zn adsorption onto Irish Fucus vesiculosus: Biosorbent uptake capacity and atomistic mechanism insights.

This study presents a multifaceted approach of Zn adsorption onto dry Fucus vesiculosus originating from the Irish Sea. Metal chemistry as well as algae surface charge properties were characterized before adsorption. Zn adsorption tests were run as function of: pH, algae concentration and metal source. A comparison with Co, Cd, and Cu adsorption - in mono-ion solutions was also performed. Adsorption kinetics, fitted with pseudo-first order (PFO) and pseudo-second order (PSO) kinetic model, allowed the uptake parameters to be found and a comparison of kinetic rates. Synchrotron X-Ray-Florescence and X-Ray Absorption Spectroscopy measurements of Zn on algae after exposure permitted the extraction of direct information about Zn spatial distribution and bonding environment. The results showed that the carboxylic groups are the ones involved in the heterogeneously distributed Zn adsorption at low pH, Zn being coordinated with 5-6 O at bond distances varying from 1.98 to 2.03 Å - as in Zn alginate. Synchrotron results provide confirmation that, relative to Zn, alginate is one of the main algae components responsible for metal binding.