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Method of processing hydrolysed sodium arsenite into commercial product Method of processing hydrolysed technical sodium arsenite into a commercial product involves cyclic repetition of consecutive steps. First, arsenic salts are leached from material with hydrochloric acid solution, which is added until achieving pH 9.5-10.5, to form a heterogeneous system. The heterogeneous system is then divided into a solid phase and a working solution. Further, the working solution is concentrated through evaporation to arsenic (III) content greater than 10 g/100 g water and the concentrated working solution is separated from the formed precipitate. Arsenic (III) oxide is precipitated by acidifying the working solution and the arsenic (III) oxide precipitate is filtered off. The filtrate is returned to the first step of the process. After repeating the cycle of said operations 3 to 10 times, arsenic (IV) compounds are then extracted from the working solution via reduction thereof to arsenic (III) compounds or to elementary arsenic. |
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Method of processing nonferrous metallurgy wastes containing arsenic and sulphur Invention can be used when recycling cakes, sludge and dust formed when processing nonferrous metal ore containing arsenic and sulphur. The method of processing nonferrous metallurgy wastes involves loading a mixture, firing said mixture and crystallisation of arsenic trioxide. Before loading into a furnace, the mixture is prepared by loosening, mixing with a soda or lime additive, drying at temperature of 160-200°C to moisture content of not more than 4% of the mass of the mixture. The mixture is fired in two steps. At the first step, the mixture is subjected to weakly oxidative firing in a horizontal revolving tube furnace at initial temperature in the region of loading the mixture of 300°C and final temperature in the region of discharging cinder of 900°C. At the second step, gases coming out of the firing furnace are subjected to post-oxidation with oxygen in a post-oxidation chamber at temperature of 600-630°C. Gases coming out of the chamber are cleaned from cinder dust in a hot electrostatic filter. Arsenic trioxide is crystallised in a settling chamber which consists of series-arranged pre-chamber, crystalliser and tail chamber. Gases coming out of the settling chamber are cleaned from arsenic trioxide particles in a cold electrostatic filter. The cleaned gases are fed to a sulphuric acid production line. |
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Method of treating waste water from arsenic Invention can be used in industry when treating waste or natural water from arsenic. The method involves use of a composite sorbent which contains as the sorbing component iron hydroxide particles which are immobilised on organic fibres, bringing the sorbent into contact with water to form insoluble arsenic compounds and separating the treated water from solid treatment products. In the sorbent, iron hydroxide particles are immobilised by cellulose fibres during chemical deposition thereof in an aqueous dispersion of said fibres. Waste water is brought into contact with the sorbent by mixing to form a suspension of solid treatment products containing arsenic. The cellulose fibres contain, wt %: at least 94% fibres with length of not more than 1.23 mm and at least 54% fibres with length of not more than 0.63 mm. The sorbent has the following composition, pts.wt: cellulose fibres -100, iron hydroxide - 20-500. Water treatment is carried out at sorbent concentration of 40-300 mg/dm3. Separation of the treated water from solid treatment products is carried out by pressure flotation, wherein the flotation sludge or a portion thereof is fed into the water treatment process. |
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Method of producing sodium arsenate Method of producing sodium arsenate involves electrolysis of water-alkaline solutions. Iron (III) hydroxide undergoes electrodialysis separation from sodium arsenate and arsenite, and spent iron hydroxide, which contains sodium arsenate and arsenite, is treated with 0.5 n Na2CO3 solution. The anode chamber is filled with 0.01 n sodium hydroxide solution and current density is set at 0.069 A/cm2. The process takes place in a double-chamber electrolysis cell with an anion exchange membrane for 1.5 hours. |
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Invention relates to the field of chemical weapons destruction, namely to methods for conversion of reaction masses (RM) produced in process of lewisite destruction by method of alkaline hydrolysis, and also products produced from RM in evaporation - "hydrolytic sodium arsenite" (HAS), or in electrolysis of RM - spent catholyte. Method includes filtering of initial product from water-insoluble substances, concentration of filtrate by evaporation to produce solution of sodium arsenite in concentration of 25.0-30.0 wt %, separation of sodium chloride deposit by means of filtration, neutralisation of sodium arsenite solution to produce arsenic oxide and its treatment by method of repulping, dissolution of sodium chloride deposit in water and treatment of produced solution from arsenic compounds, at the same time sodium chloride solution is cleaned from arsenic compounds by means of their recovery into element arsenic, recovery agent is represented by thiourea dioxide, or sodium or zinc dithionite, or their mixtures, which is taken in the ratio of 2.1-2.5 per 1 relative to total arsenic, and process of recovery is carried out in the range of temperatures from 20 to 100°C, produced element arsenic is cleaned by method of repulping. In process of arsenic oxide production, arsenic compounds (V) are recovered in arsenic compounds (III) at pH of medium equal to 3-4 with a recovery agent taken in the ratio of 1.5-2.5 per 1 relative to arsenic (V), at the same time recovery agent is represented by sulphite, or bisulphite, or sodium pyrosulphite, or rongaite or their mixtures. Process of arsenic oxide and element arsenic repulping is carried out with diluted solutions of mineral acids and water in ultrasonic field. On completion of element arsenic repulping process solution is filtered, deposit of element arsenic is washed on the filter with ethyl alcohol, then pressed in die with pressure of at least 70 kN and finally dried in vacuum at the temperature from 20 to 200°C. Solutions are filtered through a layer of microcellulose and carbon-fibre fabric of 0.5-3.0 cm, which makes it possible to separate water-insoluble substances, dying admixtures and metal admixtures. |
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Method of producing highly pure arsenic Invention can be used in electronic industry, in optical and semiconductor engineering, glass manufacturing and in chemical industry as a catalyst additive. Trialkylarsenites of general formula (RO)3As, where R = CH3, C2H5, are reduced using hydrazine from the "pure" or "highly pure" category with molar ratio of esters to hydrazine equal to 1:3-1:3.2 and temperature (70-100)°C or hydrazine hydrate from the "pure" or "highly pure" category with molar ratio of esters to hydrazine hydrate equal to 1:3-1:6 and temperature (130-150)°C. Precipitate of amorphous arsenic is filtered off, washed and dried. |
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Method of producing arsenic acid Sludge from production of non-ferrous metals, containing arsenic, sodium, zinc and cadmium compounds, is dispersed in water with mass ratio solid:liquid = 1:(2.5-3). Small portions of nitric acid are added to the obtained suspension until attaining concentration of HNO3 from 15 to 20 g/dm3. While stirring, the mixture is heated to temperature ranging from 70 to 90°C and held while stirring for 2 to 3 hours. The residue which contains arsenic compounds and elementary sulphur is filtered from the mother solution which contains sodium, zinc, iron and copper sulphates. The residue is washed and water is added until attaining mass ratio solid:liquid=(1-2):(1-3). Nitric acid is added to the obtained solution until attaining pH = 1.5-2 and hydrogen peroxide is added in stoichiometric quantity of 105 to 110%. |
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Invention can be used in hydrometallurgical industry, as well as in recycling lewisite group toxic substances at facilities for destroying chemical weapons. Caustic soda and thiourea dioxide in crystalline or solution form are periodically added to an aqueous solution of sodium arsenite or products of lewisite detoxification. The reaction is carried out at temperature between 40 and 80°C. The solution is stirred for 120 minutes. Elementary arsenic is separated from the liquid phase, washed with water and dried. |
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Invention refers to the chemical engineering in particular to the treatment and production of arsenic-containing products. The method for reduction of arsenic (v) compounds containing in the products of lewisite alkaline hydrolysis includes sequential input to the acidated solution of reaction mass of the potassium or sodium iodide in the amount equal to 10±0.2% of the amount necessary for complete reduction of arsenic acid to arsenic (III) compounds and ascorbic acid or hydrazine in the amount necessary for complete reduction of arsenic (V) compounds to arsenic (III) compounds. The reduction process is carried out during 0.5-2 hrs at the temperature 60-70°C and stirring. |
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Method of lithium hexafluorarsenate production Invention can be used in production of lithium hexafluorarsenate applied in chemical current sources. Method of lithium hexafluorarsenate production includes interaction of hexafluorarsenic acid derived from aqueous solutions of high-purity arsenic and hydrofluoric acids, and lithium carbonate with water-binding agent acetic anhydride at temperature (55±5)°C in molar ration as follows: H3AsO4:HF:(CH3CO)2O:Li2CO3=1:(6.1÷6.5): (16÷17:(0.5÷1). Derived reaction mass is separated from lithium hexafluorarsenate industrial salt by acetic acid distillation to solid residue. Lithium hexafluorarsenate commercial-grade salt is produced with purification of industrial salt and recrystallisation from ethyl acetate. Produced high-purity lithium hexafluorarsenate contains, wt %: base material 99.98, water 0.02, trace contaminant 10-4-10-5. |
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Method of cleaning arsenic-polluted solvents Invention relates to treatment of waste waters and solvents containing significant amounts of hydrochloric or sulfuric acid and arsenic and can be used in metallurgy, especially in manufacture of nonferrous metals, as well as in chemical industry. Method consists in that arsenic is precipitated by sulfide-containing reagent, e.g. sodium hydrosulfide, said sulfide-containing reagent being added to solution to be treated from below while simultaneously stirring the solution. Specific weight consumption of the reagent is not higher than 1.5 kg*S-2*h-1. Hydrodynamic regime of stirring is maintained within the Reynolds number range 600 to 6000. Precipitation of arsenic is effected until its residual concentration in solution not below 0.03 g/dm3. Addition of sulfide-containing reagent is stopped when redox potential value is achieved in the curve break point on diagram depicting consumption of the reagent as function of arsenic concentration in solution. |
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Installation for preparation of the arsenic-containing sulfide wastes for the storage The invention may be used at preparation of the industrial arsenic-containing sulfide wastes for the storage. The installation for preparation of the arsenic-containing sulfide wastes for storage includes: the waste bin (1), the fitting pipe (3) used for the wastes feeding from the bin, is connected to the feeder (4) with the loading device (5) of the press (2) used for forming the cakes from the wastes. The unloading device (6) of the press through the system of the pushers (7), (8) is connected to the conveyor (9) of the device used for deposition of the protecting coating on the cakes. The device for deposition of the protecting coating on the cakes also includes the unpowered roller conveyor (10), which rollers (11) are dipped in the liquid bitumen, and the spattering device (14) located above the unpowered roller conveyor is connected by the heated pipeline with the liquid bitumen heated tank (17). The ventilation roof hood (7) is installed over the conveyer and the system of the pushers and is linked by the ventilation duct through the filter (28) to the loading device of the press. Over the unpowered roller conveyor (10) there is the ventilation roof hood connected with open air by the ventilation duct through the additional filter (32). The block of cooling of the bituminized cakes includes: the transporter (21) connected to the unpowered roller conveyor (10), the sprinkler (22) located over the transporter(21) connected to the water cooling device (24). The invention allows to reduce the danger of the arsenic-containing cakes. |
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Especially pure arsenic acid production process Invention relates to producing arsenic acid, which serves as starting material for obtaining pure arsenic-containing substances usable as chemical power sources as well as additive in optical glass manufacturing processes. Process of invention envisages oxidation and simultaneously hydrolysis of tri-lower alkyl arsenites of general formula (RO)3As (R = Me, Et, Pr) with aqueous hydrogen peroxide solution at 10 to 50°C and (RO)3As/H2O2 molar ratio 1:(1-3). Resulting reaction mass is distilled to remove alcohol water. Commercial especially pure arsenic acid is obtained after evaporation of its solution. |
Another patent 2528994.