Fast Procedure for Removing Silver Species in Waters Using a Simple Magnetic Nanomaterial

Abstract

The increase in the production and use of disinfectants containing silver atoms (in both its ionic and nanomeric forms) in their formulation, due to the global pandemic situation caused by COVID-19, has increased the presence of silver species in wastewater. Moreover, silver atoms are now considered as emerging pollutants in water. In this work, we propose a novel method for the instantaneous and simultaneous removal of ionic and nanomeric silver in water samples, using a previously unpublished methodology consisting of the in situ formation of magnetic nanoparticles in the aqueous samples to be treated. While the nanoparticle precursors react to form them, the silver atoms present in the sample are adsorbed onto them due to a strong electrostatic interaction. As the final nanoparticles are magnetic, they can be easily removed from the aqueous medium using a magnet, leaving the samples free of silver species. The innovative feature of the method is that the adsorbent is synthesized in situ, within the sample to be treated, making the approach a low-cost, easy-to-perform solution. Temperature, contact time, dose of Fe3O4, and concentration of nanomeric and ionic silver were investigated. The results showed that at 50 °C, 100% of both silver species were removed from the water samples simultaneously. The surface of Fe3O4 was characterized before and after the application of the removal process using energy-dispersive X-ray spectroscopy and Field Emission scanning electron microscopy. Adsorption kinetics and equilibrium isotherms studied reveal a Langmuir-type physicochemical process. The procedure has been applied to different water samples (river and drinking water) with excellent results, making the method a new standard for the removal of ionic and nanomeric silver. In addition, the nanoparticles formed could be recycled and reused for other analytical and decontamination purposes.