Development of highly functionality magnetites and their application to removal of arsenic

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New functional magnetites were prepared by addition of elements such as Zr, Si, Mg, Ce and Ti to magnetite, and their applications to arsenic adsorption were investigated. Although the Si-magnetite has high specific surface area and high performance for arsenic removal, it cannot be used for removal of arsenic in groundwater because Si was eluted from the Si-magnetite. On the other hand, the zero point of charge of pH (PH_<zpc>) of Zr, Ce and Ti-magnetites were in the neutral pH range and they have high specific surface areas. The important factors for arsenic removal, pH_<zpc> and specific surface area were controlled by introducing different elements and mole ratios of element/ Fe when magnetites were prepared. The addition of Zr, Si, Mg, Ce and Ti cause the low crystal-growth rate of the magnetites to result in the amorphous structures. Adsorption properties for arsenic were investigated using Zr, Ce and Ti-magnetite. It was shown that Zr, Ce-magnetite effectively removed arsenic from its low concentration Ti-magnetite with Ti /Fe = 1 has a high specific surface area, 240m^2/g and the adsorption capacities of As (V) and As (III) were 0.85 and 1.2, respectively. These results were 4 - 6 times of the adsorption capacity of arsenic of the previously reported magnetites.