Simultaneous adsorption of mercury species from aquatic environments using magnetic nanoparticles coated with nanomeric silver functionalized with L-Cysteine

We introduce a novel, efficient and fast method for the total and simultaneous removal of monomethylmercury, dimethylmercury, ethylmercury and Hg (II) from aquatic environments using magnetic core nanoparticles, coated with metallic nanomeric silver and functionalized with L-Cysteine. As far as the authors know, simultaneous removal has not been achieved previously. The experimental design was based on exploring a wide range of experimental conditions, including pH of the medium (2-12), contact time (up to 20 min), adsorbent dose (50-800 mu L) and temperature (293-323 K), in order to achieve the highest adsorption efficiency. The results show that, for a pH equal to 6.2 at room temperature, 400 mu L of nanoparticles is sufficient to achieve 100% adsorption efficiency for all the studied Hg species after a contact time of 30 s. The adsorbent was characterized by means of Scanning Electron Microscopy, Energy Dispersive X-ray Analysis, Fourier-Transform Infrared Spectroscopy and a BET test. Moreover, the procedure allows the total recovery and recycling of the nanoparticles using 50 mu L of 0.01 M KI. As regards reuse, the adsorbent exhibits no loss of adsorption capacity during the first three adsorption cycles. Thermodynamics reveals that adsorption is of a physicochemical nature, the equilibrium isotherms being described by a Langmuir model for all the Hg species. The ability of the method to simultaneously adsorb all species of mercury present in water, achieving full adsorption in just a few seconds, along with the simple experimental conditions and its cost-effectiveness, strongly support the approach as an alternative to current procedures.

Automated summary

A novel method using magnetic core nanoparticles, coated with metallic nanomeric silver and functionalized with L-Cysteine, has been introduced for the total and simultaneous removal of various mercury species from aquatic environments. The experimental results show high adsorption efficiency within a short contact time, along with the ability to recover and reuse the nanoparticles. The thermodynamics reveal that the adsorption is of a physicochemical nature, and the equilibrium isotherms are described by a Langmuir model for all the Hg species.