28 January 2011
An iron-rich, porous material can remove arsenic from drinking water in under two hours, say Chinese scientists.
Arsenic is notoriously toxic, proving fatal to the majority of living organisms in high doses. Elevated levels of arsenic in groundwater in countries such as Bangladesh pose a serious threat to human health. But traditional methods to remove the arsenic struggle to eliminate the more dominant arsenic ion, arsenite.
Now, Kang Li and colleagues from Harbin Medical University have removed arsenite from water samples using ferrihydrite - a low cost, natural mineral found on the Earth's surface. Already known to absorb arsenic, its efficiency is usually hindered by its low surface area. The team overcame this by combining two layers of ferrihydrite, increasing its surface area and loading capacity. Arsenite was selectively removed from water, even in the presence of other anions with similar molecular structures. Removal of the arsenite from the surface of the ferrihydrite material was easily achieved by washing it with an alkali solultion. After a heat treatment, the mesoporous material could be reused up to ten times.
Elevated levels of arsenic in drinking water pose a serious threat to human health
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Li believes that the recycling aspect holds the greatest challenge for future practical applications for the material. 'If magnetic nanoparticles could be loaded in the channels of the two-line ferrihydrite, recycling would become even easier,' he says.
'The next step should be related to the investigation of the mechanism and efficiency of arsenic removal by nanocrystalline iron oxides depending on their structure and crystallinity,' says Radek Zboril, an expert in nanocrystalline iron oxides from Palacky University in the Czech Republic.
'The incorporation of arsenic into the structure of the in situ formed iron oxide nanoparticles seems to be a more promising way from the viewpoint of real applications.'