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Friday, 02 March 2012

Gold nanoparticles for removing mercury from polluted water

ICN researchers and colleagues report in ACS Nano a gold nanoparticle-based system to remove mercury(II) from water. The system generates an easily removable and recyclable precipitate.

"Citrate-Coated Gold Nanoparticles As Smart Scavengers for Mercury(II) Removal from Polluted Waters". (Puntes, Ojea-Jiménez, et al., ACS Nano, 2012, 6 (3), 2253–2260)

Researchers at ICN, the Institute of Materials Science of Barcelona (ICMAB) and the National Autonomous University of Mexico (UNAM) have engineered gold nanoparticles that selectively remove mercury(II) from water. The team, led by ICN Group Leader Victor Puntes, who is an ICREA Research Professor and Professor at UAB, have just reported their findings in the journal ACS Nano, in which they describe the efficacy of their system at removing mercury(II) in purified laboratory water (milliQ) and in natural river water (Ebro river, Flix, Spain) containing very low levels of mercury.

The gold nanoparticles act as scavengers, flowing throughout the water sample to seek out mercury(II) ions against a background of other metal ions, including copper(II), iron(III), potassium, magnesium or sodium. The process involves chemisorption of mercury(II) onto the nanoparticles, its reduction to mercury(0) and formation of an easily removable gold amalgam (Au3Hg) precipitate.

Much of the world's population does not have access to clean drinking water, in part due to industrial pollutants such as the extremely toxic metal mercury, mostly in the form of mercury(II). Thus, there is an urgent demand for safe, effective, low-cost and portable methods to purify water. For example, stricter environmental regulations have generated interest in processes to remove mercury from streams containing relatively low (< 100 ppb) concentrations of mercury.

The gold-citrate nanoparticles devised by Puntes and his co-workers fit this profile quite well: they can be employed at treatment plants or at the site of contamination, and used in continuous flow operations. Furthermore, the gold amalgam precipitate can be readily processed to recover the gold, thereby offsetting its relatively high price, and to isolate the mercury for proper treatment and/or disposal.

The lead author of the ACS Nano paper was ICN researcher Isaac Ojea. The article can be accessed through the link above.

The article can be accessed here.