Application of iron based nanoparticles as adsorbents for Arsenic removal from water

Arsenic contaminations of groundwater in several parts of the world are the results of natural and/or anthropogenic sources, and have a large impact on human health. Millions of people rely on groundwater for drinking water supply; therefore, contamination of these sources represents a strong limitation to their civil and urban development. Due to the toxicity and potential carcinogen effect, in 2001 the World Health Organization has reduced the maximum allowable concentration of arsenic in drinking water to 10 μg/L. This new limit has been then adopted by numerous countries, such as Italy. Among the methods used to reduce arsenic concentration, the adsorption process has often proved to be the most suitable in the case of drinking water sources. Adsorption efficiency strongly depends on the type of adsorbents. In the case of arsenic contaminated groundwater, a number of media have been tested so far (alumina, iron-based), some of which providing good removal. However, there is still an high interest in new media capable of providing better performances, i.e. longer duration of the column plants where the adsorption process is usually implemented at the full-scale. Recently there has been increasing interest on the application of nanoparticles and nanostructured materials as efficient and viable alternatives to conventional adsorbents in the removal of metals from water. Due to their small size, they possess a large surface area and a high surface area to volume ratio. These characteristics improve the adsorption capacity of the nanoparticles and make them potentially suitable for the application where higher removal efficiency are required. The present work investigates the application of a new nano-adsorbent for arsenic removal from water. The media was produced in laboratory and made by magnetite nanoparticles. These iron-based nanoparticles, characterized by a very small size (9 nm), showed high removal rate, providing a specific adsorption capacity at equilibrium of about 8.25 [mg As/g ads]. Among the investigated models, the pseudo-second order best fitted the experimental data of the kinetic tests. Comparisons made with the performance provided by commercial adsorbents and other materials confirms the use of magnetite nanoparticles for the removal of arsenic as a promising technique.