This study investigated the structure, mineralogical specifics and chemical composition, of a natural and modified diatomite ore, which obtained from the Aktyubinsk /Kazakhstan deposits by using SEM, XRF, XRD, FTIR, TGA and SDTA. Three modified forms of diatomite's were prepared by calcinations at 900 o C and/or calcinations and acidification by 0.5 N HCl (D, D-HCl, D-900 and D-900-HCl). The iron(Fe 2 O 3) and silica (SiO 2) contents in natural raw diatomite were about 3.9 % and SiO 2 80.23 % respectively. Whereas, the modified diatomite which treated with 0.5 N HCl followed calcination at 900 o C revealed 0.92% and 84.75% of Fe 2 O 3 and SiO 2 respectively. This proved that the elimination of the impurities which may be found as clay minerals, especially mica and kaolinite. The SEM micrographs investigation of acid activation and/or acid activation followed by calcinations showed the original geometry of the pores to be preserved, but there is collapse in the skeleton structure.
Iron hydroxide supported onto porous diatomite (D-Fe) is a low-cost material with potential to remove arsenic from contaminated water due to its affinity for the arsenate ion. This affinity was tested under varying conditions of pH, contact time, iron content in D-Fe and the presence of competitive ions, silicate and phosphate. Batch and column experiments were conducted to derive adsorption isotherms and breakthrough behaviours (50 μg L(-1)) for an initial concentration of 1,000 μg L(-1). Maximum capacity at pH 4 and 17% iron was 18.12-40.82 mg of arsenic/g of D-Fe and at pH 4 and 10% iron was 18.48-29.07 mg of arsenic/g of D-Fe. Adsorption decreased in the presence of phosphate and silicate ions. The difference in column adsorption behaviour between 10% and 17% iron was very pronounced, outweighing the impact of all other measured parameters. There was insufficient evidence of a correlation between iron content and arsenic content in isotherm experiments, suggesting that ion exchange is a negligible process occurring in arsenate adsorption using D-Fe nor is there co-precipitation of arsenate by rising iron content of the solute above saturation.
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