Selective and efficient mercury(II) removal from water by adsorption with a cellulose citrate biopolymer

Mercury is a global pollutant, very dangerous for the aquatic ecosystems and for human health. The sources of mercury in the environment are either anthropogenic or natural. However, historical mining activities and current anthropogenic activities, have led to a significant increase of its level in the environment. Its removal by efficient and cost-effective technologies, is of the utmost importance in order to help restore it back towards natural levels. Here we show that a novel cellulose citrate biopolymer, produced by the reaction of cellulose and citric acid, is an efficient adsorbent of inorganic mercury with a distribution constant close to 10⁵ l/g and an estimated record high maximum adsorption capacity of 1600 mg/g. Moreover, due to the large fraction of citrate moieties on its surface, its adsorption selectivity toward inorganic mercury, is the highest after that for Pb(II), among a series of divalent heavy metals, in different aqueous matrices. Finally, cellulose citrate can be reused for several adsorption cycles by a simple regeneration process without significant adsorption performance loss.