Ksenia Machekhina

Colloid stability of iron compounds in groundwater of Western Siberia

The paper reports on experimental modeling of the colloid system composition in natural groundwater. Iron hydroxide is found to be the main component of natural colloid systems. It is shown that silicon compounds and dissolved organic substances (DOS) stabilize iron hydroxide (III), forming a stable colloid system, and preclude coagulation. The presented results suggest that CaCl2 and AlCl3 electrolytes affect the coagulation stability of synthesized model colloid solutions.

Method of removal of colloid iron from groundwater of Western Siberia region by using of carbon dioxide

Water objects of Siberia north contain impurities in water in colloid form. The impurities are stable to physical and chemical influence. Search ways of decreasing of natural colloid solutions stability is topical issue. Destruction of colloid particles makes it possible to produce qualitative potable water. In the present work factors influenced on aggregate stability of colloid solutions are represented. It is shown that a disperse phase of natural colloid systems consists of iron and silicium ions and humic organic substances in the ratio 5.6 mg/L:20 mg/L:2.2 mg/L, respectively. Calculated electrokinetic potential of colloid solutions is in the range from -23 up to -32 mV. Stability of colloid iron is studied at the presence of CaCl2 and AlCl3 electrolits. Coagulation thresholds of CaCl2 and AlCl3 are equal to 1.25 mmol/L and 0.0074 mmol/L, respectively. Furthermore, it is shown pH is also influenced on stability of the colloid system. When pH of solution is 4.5 colloid iron system coagulates. This fact allows developing a method of removal of colloid iron by temporal decreasing of pH by using of carbon dioxide. This method is ecologically safe and allows simplifying technology of water-preparation due to exception of the thin filtration which is used for removal colloid particals. The pH renewal is spontaneous process which is going while carbonization is going. Thermodynamic calculations of reactions describing the destruction mechanism of colloid iron are represented.

Destruction of humic substances by pulsed electrical discharge

Currently, the water recourses in the territory of Tomsk region are groundwater which is limited to the high concentration of iron and manganese ions and organic substances. These impurities present in water in different forms such as soluble salts ant the colloid forms. Therefore, the present work is a part of a continuations researcher of the processes in natural waters containing humic substances at the influence of pulsed electrical discharges in a layer of iron pellets. It is shown that the main stage of water purification process of humic substances during treatment by pulsed electric discharge in the layer of iron granules is a difficult process including several stages such as formation of iron oxyhydroxide colloid particles, sorption and coagulation with humic macromolecules substances, growth of particle dispersed phase and precipitation. The reason for the formation and coagulation of the dispersed phase is a different state of charge of the colloid particles (zeta potentials of (Fe (OH)3) is +8 mV, zeta potentials of (Humic substances) is -70 mV. The most intense permanganate oxidation reduction to the maximum permissible concentration occurs at the processing time equal to 10 seconds. The contact time of active erosion products with sodium humate is established and it equals to 1 hour. The value of permanganate oxidation achieves maximum permissible concentration during this time and iron concentration in solution achieves maximum permissible concentration after filtration.

Influence of Copper Nanoparticles on Tribological Properties of Nanolamellar Tungsten Disulfide

Tribological properties of a composite mixture based on copper nanoparticles and nanolamellar tungsten disulfide powder have been studied. SEM of copper nanoparticles produced by electrical explosion of wires was analyzed. The tribological tests of pure tungsten disulfide and composite WS2-Cu lubricant are performed. Possible mechanism of copper influence to tribological properties of tungsten disulfide was discussed.

Removal of Iron Colloid Substances from Aqueous Solutions Using Pulsed Corona Discharge

Pulsed electric discharge has been used for the removal of iron colloid substances from aqueous solutions. The residual concentration of organic substances in aqueous solution depends on the pulse repetition rate. The maximum decrease in organic substances concentration was observed at the pulse repetition rate of 800 pps. Comparison of the results obtained for iron colloid solutions containing humic substances and solutions of humic subtances with no colloids shows that the highest removal efficiency of organic substances was obtained when no iron and silicon ions were present in the solution. The results of our experiments suggest that pulsed electric discharge treatment for the removal of organic substances from natural waters is more efficient at an after-treatment stage, after precipitation of colloid substances.

Two-Step Synthesis of Tungsten and Molybdenum Disulfides

Efficient two-step technique of tungsten and molybdenum disulfides obtaining from metal nanopowders produced by EEW and elementary sulphur is described. Tungsten and molybdenum nanopowders surface area dependence on wire length is studied. Features of metal and sulphur combustion process are discussed. It is determined sulphur excess in reagents 15 wt.% results in mono-phase metal disulfide formation with small free sulphur concentration in reaction products.

Study the properties of activated carbon and oxyhydroxide aluminum as sorbents for removal humic substances from natural waters

The present work relates to the problem of high-quality drinking water supply using processes of adsorption on activated carbon and aluminum oxyhydroxide for removal humic- type organic substances. Also the paper reports on sorbtion properties of the activeted carbon Norit SA UF and oxyhydroxide aluminum for removal humic substances. It was found out that the maximum adsorption capacity of activated carbon to organic substances is equal to 0.25 mg/mg and aluminum oxyhydroxide is equal to 0.3 mg/mg. It is shown that the maximum adsorption capacity of activated carbon Norit SA UF to iron (III) ions is equal to 0.0045 mg/mg and to silicon ions is equal to 0.024 mg/mg. Consequently, the aluminum oxyhydroxide has better adsorption characteristics in comparison with the activated carbon for removal of humic substances, iron and silicon ions. It is associated with the fact that activated carbon has a large adsorption surface, and this is due to its porous structure, but not all molecules can enter into these pores. Therefore, the fibrous structure of aluminum oxyhydroxide promotes better sorption capacity. The presented results suggest that activated carbon Norit SA UF and aluminum oxyhydroxide can be used as sorbents for removal humic substances or other organic substances from groundwater and natural waters.

Electropulse treatment of water solution of humic substances in a layer iron granules in process of water treatment

The present work is a part of a continuations study of the physical and chemical processes complex in natural waters containing humic-type organic substances at the influence of pulsed electrical discharges in a layer of iron pellets. The study of humic substances processing in the iron granules layer by means of pulsed electric discharge for the purpose of water purification from organic compounds humic origin from natural water of the northern regions of Russia is relevant for the water treatment technologies. In case of molar humate sodium - iron ions (II) at the ratio 2:3, reduction of solution colour and chemical oxygen demand occur due to the humate sodium ions and iron (II) participation in oxidation-reduction reactions followed by coagulation insoluble compounds formation at a pH of 6.5. In order to achieve this molar ratio and the time of pulsed electric discharge, equal to 10 seconds is experimentally identified. The role of secondary processes that occur after disconnection of the discharge is shown. The time of contact in active erosion products with sodium humate, equal to 1 hour is established. During this time, the value of permanganate oxidation and iron concentration in solution achieves the value of maximum permissible concentrations and further contact time increase does not lead to the controlled parameters change.

Study of adsorption process of iron colloid substances on activated carbon by ultrasound

The paper reports on the adsorption of iron colloid substances on activated carbon (PAC) Norit SA UF with using ultrasound. It is found that time of adsorption is equal to three hours. High-frequency electrical oscillation is 35 kHz. The adsorption capacity of activated carbon was determined and it is equal to about 0.25 mg iron colloid substances /mg PAC. The iron colloid substances size ranging from 30 to 360 nm was determined. The zeta potential of iron colloid substances which consists of iron (III) hydroxide, silicon compounds and natural organic substances is about (-38mV). The process of destruction iron colloid substances occurs with subsequent formation of a precipitate in the form of Fe(OH)3 as a result of the removal of organic substances from the model solution.

Effect of Humic Substances and Silicon Ions on Stability of Iron Hydroxide (III) Nanoparticles

The paper reports on experimental modeling of the colloid system composition in natural groundwater. It is shown that the stability of iron hydroxide nanoparticles relates to the presence of silica and humic substances. It was found out the molar ratio of iron/silicon/organic substance is equal to 1/7/2, where stable iron (III) hydroxide nanoparticles form. The iron hydroxide nanoparticle size ranging from 30 to 600 nm was determined. It characterizes the steady state of the colloidal system.