The paper reports on experimental modeling of the colloid system composition in natural groundwater. No. 3?-?IC?+?silicon compounds (SC); Solution No. 4?-?IC?+?DOS?+?SC. Stability of the synthesized solutions was estimated from variation in optical density of the solutions, iron colloid concentration in the solutions, -potential, and particle size. Simplest model solution No. 1 was prepared by dissolving FeSO4??7H2O in water. The concentration of iron ions in solution No. 1 was 5.6 mg/L 517-28-2 IC50 and corresponded to the iron concentration in the groundwater of the Western Siberian region. The pH value in the solution was kept at 10.0??0.2 and was taken from measured optimum iron (II) concentration in the solution, sedimentation rate, and system redox potential. The iron (II) concentration in model colloid solution No. 2 was 5.6 mg/L. The concentration of DOS, which stabilized colloid iron substances, was 0.054.0 mg/L. This DOS concentration corresponded to that in the groundwater of the Western Siberian region. Model colloid solution No. 3 was synthesized with the same iron concentration; the silicon concentration was varied in the range 520 mg/L and corresponded to the silicon concentration in the groundwater of the Western Siberian region. Model solution No. 4 was synthesized with iron (II) ions, DOS, and silicate ions. As shown by analysis of solution No. 2, the particle size in the dispersed 517-28-2 IC50 phase of the model solution does not depend on the DOS concentration; therefore, the DOS concentration was 4 mg/L. The iron concentration in the solution, like in the others, was constant and was 5.6 mg/L. The silicon concentration was varied in the range 520 mg/L. All model solutions were synthesized at room temperature. A shaker GFL 3005 (Germany) with a shaking frequency 100 rounds/min was used for mixing. Results and discussion Chemical composition and groundwater indicators in the Western Siberian region The chemical composition and the groundwater indicators, such as pH value and water color, were measured in the groundwater of Beloyarsky, Kargasoksky, and Strezhevskoy areas and southern areas of the Tomsk region. Table?1 shows the chemical composition and the groundwater indicators in the north and south of Western Siberia. Table 1 Chemical composition and groundwater indicators of the Western Siberian region The data in Table?1 suggest that the groundwater in the Western Siberia region features high concentration of iron, manganese, silicon, and dissolved organic substances. The iron concentration is typically higher than the maximum permissible concentration (MPC). It is possible to define impurities that make most critical contribution to the formation of colloid compounds. First, the groundwater contains iron in the form of Fe(II) ions. During oxidation, slightly soluble iron hydroxide (III) appears in the colloid form; the properties of this colloid are well studied (Richard 2004; Paul and Raj 1997). Second, these are humic organic substances which assist the formation of stable iron-containing colloid systems (Serikov et al. 2009). Third, there are silicon Rabbit Polyclonal to SPTA2 (Cleaved-Asp1185). compounds which can also contribute to the formation of colloid compounds both with iron compounds and with organic substances (Crittenden et al. 2012). Thus, we selected iron, silicon, and humic organic substances for synthesizing model solutions and for studying properties of colloid substances in groundwater. Synthesis of model colloid solutions Stability of the synthesized solutions No. 1 was estimated from variation 517-28-2 IC50 in optical density of the solutions, iron colloid concentration in the solutions, -potential, and particle size. It is shown that at a pH value of 10.0??0.2 and Fe2+ concentration of 5.6 mg/L, sedimentation occurs in 30 min (c?=?30 min) and the 517-28-2 IC50 system redox potential changes from -80 to +20 mV. The measurements were taken immediately after preparation of the solution. The results demonstrate that the particle size is larger than 1 m and the –potential.