Lanthanum functionalized highly ordered mesoporous media: implications of arsenate removal

Human activities and natural processes release arsenic into ground and surface waters creating potentially serious environmental problems for humans and other living organisms [1]. In recognition of this threat, a new arsenic limit of 10lg/l, lowered from the current 50g/l, will become effective in 2006 for drinking water systems in the United States. Consequently, there is an urgent demand for an economical, highly effective, and reliable technique that is capable of meeting this new maximum contaminant level for arsenic. Many adsorbents have been developed for arsenic removal since adsorption is considered a promising technology, due in part to its ease of set up [2–5]. Activated alumina has been one of the best available adsorbents for point-of-entry/point-of-use (POE/POU) adsorption systems, and has been extensively studied due to its selective characteristics and effectiveness for arsenic adsorption [6]. However, the pH of the influent, which controls the presence of arsenic species, needs to be controlled to achieve maximum arsenic adsorption capacity. When activated alumina is regenerated, its adsorption capacity is reduced by 30–40%. Furthermore, due to a slower adsorption reaction, activated alumina requires relatively longer empty-bed contact times (3–5 min) than ion exchange resins. Therefore, a highly effective adsorbent for arsenic removal is needed.