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Technological processes of water purification in the "Izumrud" devices There is serial production of the "Izumrud" devices using the following technological processes of water purification: "Izumrud", "Sapphire", "Crystal", "Ruby" and "Aquamarine" [3-7]. They are different in the succession of water purification technological stages and are applied to purify drinking water dependant on its initial parameters. The main stages of water purification in the "Izumrud" devices are the following:
Electrolytic, as well as heterophase and liquidphase electrocatalytic oxidation in the anodic chamber of an electrochemical reactor (Anode Treatment: AT). During anode treatment, in fractions of a second, water is saturated with highly active oxidants: ClO2, ClO, HClO,1O2, O3, Cl· , H2O2·, OH·, HO2·. Their concentration may vary from 6 to 18mg/l, depending on the cycle of electrochemical treatment. The processes of direct electrolytic oxidation (on the electrode's surface) and electrocatalytic oxidation (on the catalytically active centers of the electrode's surface and in a water volume with the help of catalysts-carriers) provide the destruction of organic admixtures and microorganisms. Abnormally high values of the oxidation-reduction potential of water in the anodic chamber (over +2000 mV, measured by a platinum electrode, as compared to a chlorine-silver reference electrode - c.s.e.) as well as metastable active chlorine and active oxygen compounds taking part in the reactions rule out the formation of toxic chlorine organic substances.
Electrolytic as well as heterophase and liquidphase electrocatalytic reduction in the cathodic chamber of an electrochemical reactor (Cathode Treatment: CT). During cathode treatment, also in fractions of a second, water is saturated with highly-active reductants: Ž-, 3Ž2-, 2Ž2-, O2- , Ž2-, eaq. It leads to the formation of insoluble heavy metal hydroxides (Men+ + nOH- -> Me(OH)n) Apart from that, in the cathodic chamber direct electrolytic reduction occurs (on the electrode's surface), as well as electrocatalytic reduction (in a water volume with the help of catalysts-carriers and hydrated electrons) of multi-charge cations of heavy metals: Men++ e -> Me0. The above processes reduce water toxicity caused by the presence of heavy metals by thousands of times, thanks to their transformation into a natural, stable, biologically inactive form of existence in nature. Heavy metal hydroxides can be dissolved in strong acids, including hydrochloric acid. Normally, hydrochloric acid is present in gastric juice. But gastric juice itself, or in the presence of food bolus being digested, is a complex organic medium, containing proteins and polysaccharides. These compounds play a role of enterosorbents which easily bind hydroxide molecules. In this way, heavy metal hydroxides are protected against the action of hydrochloric acid. Therefore, they are not dissolved in the stomach but are eliminated from the body in a natural way. Similarly, enterosorbents bind the flakes of hardness salts, iron hydroxides. These components are practically harmless for the body. But their presence in drinking water changes its taste and is unwelcome due to esthetic reasons.
Controlled electro-migrational ion transport through the diaphragm of an electrochemical reactor (Ion Transport: ITa->c - from the anodic chamber to the cathodic one; ITc->a - from the cathodic chamber to the anodic one; IT - mixed). This process permits to remove excessive quantity of ions from water, among them heavy metal ions, nitrates and nitrites. Controlling the rate and selectivity of electromigrational transport is achieved by changing the electric current density, by pressure differential at the diaphragm and by choosing its optimal physico-chemical, filtration and geometric parameters (the walls' thickness in the upper and lower parts, setting it with the smaller base up or down and so on).
Heterophase catalytic destruction of active chlorine compounds and heterophase catalytic oxidation of organic substances (Heterophase Catalytic Destruction: HCD). In a catalytic reactor, on the surface of granules of the catalyst requiring no replacement and regeneration there occurs the destruction of active chlorine compounds (ClŽ2·, H‘lO·, ClO·) associated with the formation of highly-active short-living particles: O·, Ž, Cl·, OH·.They provide destructive oxidation of a wide range of organic substances, including dioxins.
Combined electroflotation and airlift water purification (Flotation Treatment + AirLift Treatment: FT + ALT). This process takes place in a flotation reactor, to which water comes usually after cathodic treatment in the electrochemical reactor, having been saturated with electrically active microbubbles of hydrogen. The hydrogen microbubbles vary between 0.2 and 10 ?m in size. The electric activity of hydrogen bubbles is caused by the fact that electrochemically active unstable products of cathodic reactions, for instance, 2Ž2-, O2- , Ž2-, eaq are accumulated on the boundary of "gas-liquid" phase division. On the same boundary, insoluble metal hydroxides and other colloidal particles are accumulated. In a standard flotation reactor, removal of gas microbubbles takes much time because of an extremely low rate of their rising to the surface. Under given conditions, the air introduced into water flow before it comes to the flotation reactor helps intensify the process of float slime removal. Big air bubbles (0.5-2.0 mm) accumulate on their surface a great number of tiny hydrogen bubbles with float slime particles stuck to them and secure their swift coming to the surface. There is no coalescence due to a considerable difference of free surface energy of hydrogen and air gas bubbles.
Liquidphase catalytic oxidation of organic compounds (Liquidphase Catalytic Oxidation: LCO). In such processes, which take place, for instance, in a reaction capacity for completing oxidation reactions after water treatment in the anodic chamber of an electrochemical reactor organic substance oxidation goes on with the help of intermediate oxidants (mediators). These substances are electron acceptors, synthesized at the anode, or electron donors, formed in the course of cathodic electrochemical reactions. The reactions of liquidphase catalytic oxidation or reduction have one thing in common, namely: the direct oxidant or reductant is generated and regenerated at the electrode of the electrochemical reactor.
Figures 1-5 demonstrate schematic flow diagrams of all types of the "Izumrud" devices. The following symbols are common for all the diagrams presented in the given figures: RFE - the RFE electrochemical reactor which consists of one or several (a unit) diaphragm flow electrolytic module elements (FEM elements); D - drainage; R - hydraulic resistance; M - mixer; S - separator to separate gas from liquid; F - flotation reactor to separate solid phase particles from liquid; C - catalytic reactor; E - intermediate capacity for the retention interval of reaction medium up to the completion of chemical reactions; W - drinking water; PW - purified water. Fig.1. Schematic diagram of water purification in the Izumrud-M device (the Izumrud water purification technology)
Izumrud process. The technological scheme of the "Izumrud" water purification process is outlined in Fig.1. Using the above-mentioned symbols of the technological processes, the succession of water purification stages can be presented as follows: AT-> LCO -> HCD -> CT. The process "Izumrud" is used to purify drinking water of normal mineralization level (0.2-1.0 g/l) from all species and forms of microorganisms, organic admixtures, for instance, phenol, as well as to neutralize heavy metal ions.
Fig.2. Schematic diagram of water purification in the Izumrud-S device (the SAPPHIRE water purification technology)
SAPPHIRE process. (Fig.2) consists of the following water purification stages: AT+ IT a->c -> LCO -> HCD. The process "Sapphire" is applied for the purification of water from all species and types of microorganisms, phenols, other organic compounds as well as for the removal of heavy metal ions: Hg 2+, Pb 2+, Cd 2+ and others from water.
Fig.3. Schematic diagram of water purification in the Izumrud-C device (the CRYSTAL water purification technology)
CRYSTAL process. (Fig.3) presents the following succession of purification stages: AT+ IT a->c -> LCO -> HCD -> CT + IT c->a . The process "Crystal" is employed to purify drinking water with somewhat elevated mineralization from all species and forms of microorganisms, organic compounds, particularly phenol, to remove excessive salts, specifically, to remove from water heavy metal ions as well as ions of nitrates, nitrites and sulfates.
Fig.4. Schematic diagram of water purification in the Izumrud-MF device (the RUBY water purification technology)
RUBY process. (Fig.4) includes the following succession of water purification stages: CT -> FT + ALT ->AT -> HCT. The given process is used to purify drinking water from all species and forms of microorganisms, toxic organic compounds, heavy metal ions, including excessive iron ions and to eliminate turbidity. In the process of purification, water preserves necessary for the human body ions of calcium, magnesium, potassium and fluorine; water is saturated with oxygen.
Fig.5. Schematic diagram of water purification in the Izumrud-KF device (the AQUAMARINE water purification technology)
AQUAMARINE process. (Fig.5) contains the following stages: CT + IT c->a -> FT + ALT -> CT + IT a->c -> HCT, and today is the most efficient one for the purification of water from all species and types of microorganisms, toxic organic compounds, heavy metal ions, including excessive ions of iron, nitrates, nitrites and for turbidity elimination. In the process of purification, water preserves necessary for the human body ions of calcium, magnesium, potassium and fluorine; water is saturated with oxygen.
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