摘要:
The invention relates to a process for the production of sodium dichromate and sodium dichromate solutions by oxidative roasting of chrome ores under alkaline conditions, leaching of the furnace clinker obtained with water or an aqueous chromate-containing solution, adjustment of the pH to from 7 to 9.5, removal of the insoluble constituents by filtration, a sodium monochromate solution being obtained, conversion of the monochromate ions of this solution into dichromate ions by acidification and crystallization of sodium dichromate by concentration of this solution, characterized in that the acidification is carried out with carbon dioxide under pressure with removal of sodium hydrogen carbonate, the remaining solution is then very largely freed from sodium monochromate by cooling to a temperature below 10.degree. C. and filtration, any monochromate ions still present in the remaining solution are converted into dichromate ions by addition of an acid and the sodium monochromate filtered off is added to the sodium monochromate solution before conversion with carbon dioxide into a sodium dichromate solution.
摘要:
A method for manufacturing alkali chromates by the reacting of chromium ore with alkali compounds and oxidation in an atmosphere containing at least 50% oxygen is described, in which the mixture consisting of chromium ore, alkali compound and optionally leaning materials is heated in a first stage in an atmosphere containing not more than 5 vol. % oxygen to a temperature between 1000.degree. and 1 400.degree. C., and in a second stage is oxidized at a lower temperature of 900.degree. to 1 070.degree. C. with supply of an atmosphere containing at least 50% oxygen.
摘要:
A method for the decomposition of chromium ore in a directly heated revolving tube is described, in which oxygen-containing gases are introduced into the revolving tube by means of below-bed nozzles.
摘要:
A process for the production of chromic acid by the multistage electrolysis of dichromate and/or monochromate solutions in two-compartment electrolysis cells, of which the anode and cathode compartments are separated by cation exchanger membranes, at temperatures in the range from 50.degree. to 90.degree. C., the dichromate and/or monochromate solutions being obtained by the digestion of chrome ores and leaching, the improvement wherein, optionally after the removal of aluminum, vanadium and other impurities, the monochromate solution obtained after leaching is adjusted at 20.degree. to 110.degree. C. to a pH value of from 8 to 12 by the addition and/or in situ formation of carbonate in a quantity of from 0.01 to 0.18 mol/l (for 300 to 500 g/l Na.sub.2 CrO.sub.4, converted with CO.sub.2 under pressure into a dichromate-containing solution, the dichromate-containing solution is introduced into the anode compartment of the electrolysis cell, a solution containing chromic acid, in which the molar ratio of Na ions to chromic acid is from 0.45:0.55 to 0.30:0.70, is electrolytically produced and the chromic acid is worked up by crystallization, washing and drying.
摘要:
A process for the preparation of sodium dichromate and sodium dichromate solutions by alkaline oxidizing roasting of chromium ores, leaching resulting roast with water, adjustment of the pH to 7 to 9.5, removal of the insoluble constituents by filtration, a sodium monochromate solution containing 300 to 400 g/l of Na.sub.2 CrO.sub.4 being obtained, conversion of the monochromate ions of this solution into dichromate ions by addition of an acid and/or by electrolysis and/or by reaction with carbon dioxide under pressure and crystallization of sodium dichromate by concentration of this solution. The improvement wherein before the conversion into a sodium dichromate solution, the sodium monochromate solution is concentrated to contents of 700 to 1000 g/l of Na.sub.2 CrO.sub.4, the monochromatic ions, the solution is subsequently freed as far as possible from sodium sulphate by cooling to a temperature of below 0.degree. C. and filtration, and the residual monochromate ions which remain in the solution are converted into dichromate ions by electrolysis and/or by reaction with carbon dioxide and/or with chromic acid.
摘要翻译:一种通过碱性氧化焙烧铬矿石,用水浸泡,调节pH至7至9.5,通过过滤除去不溶成分的方法制备重铬酸钠和重铬酸钠溶液的方法,将含有300〜 获得400g / l的Na 2 CrO 4,通过加入酸和/或通过电解和/或通过与压力下的二氧化碳反应并通过浓缩该溶液使重结晶的重结晶,将该溶液的单色离子转化为重铬酸根离子 。 改进之前,在转化成重铬酸钠溶液之前,将单色钠溶液浓缩至700至1000g / l Na 2 CrO 4的含量,即单色离子,随后将溶液从硫酸钠中冷却至 温度低于0℃并过滤,留在溶液中的残留单色离子通过电解和/或通过与二氧化碳和/或与铬酸的反应转化为重铬酸根离子。
摘要:
Process wherein the vanadium present in the chromium ore chromite is recovered as vanadium pentoxide during the course of the fusion of the chromium ore with alkali and its work-up to produce sodium chromate solution and sodium dichromate.
摘要:
A process for the preparation of alkali metal dichromates and chromic acid by the electrolysis of monochromate and/or dichromate solutions in an electrolytic cell in which the anode and cathode chambers are separated by cation exchange member, the improvement wherein the formation of deposits on the membrane is prevented comprising continuously introducing a solution containing chromate at a pH of about 3 to 10 into the cathode chamber during the electrolysis.
摘要:
A process for the production of chromic acid, comprising(a) dissolving ferrochrome in sulphuric acid and mother liquor from the subsequent crystallization of ammonium chrome alum, optionally with the addition of at least one of catholyte and anolyte overflow from the subsequent electrolysis,(b) removing undissolved constituents by filtration,(c) removing dissolved iron by the addition of at least one of ammonia and ammonium sulphate to the filtrate obtained, crystallizing iron ammonium sulphate and filtering,(d) crystallizing and filtering ammonium chrome alum from the remaining solution and returning the filtrate for dissolving ferrochrome in step (a),(e) dissolving the ammonium chrome alum in water,(f) precipitating and separating chromium-(III) hydroxide from the resulting solution by adding a base, optionally under reducing conditions,(g) dissolving the separated chromium hydroxide in chromic acid and optionally sulphuric acid so that either a single solution in chromic acid is obtained or two solutions are obtained, one in chromic acid and another in sulphuric acid,(h) separating the solution(s) from undissolved constituents, and(i) utilizing the solution of chromium hydroxide in chromic acid as anolyte in the electrolytic production of chromic acid in an electrolytic cell divided by a membrane, and either utilizing the same solution as catholyte in the above mentioned electrolytic cell divided by a membrane or utilizing the solution of chromium hydroxide in sulphuric acid as catholyte in the above mentioned electrolytic cell divided by a membrane, hydrogen and metallic chromium being deposited electrolytically at the cathode and/or chromium (II) ions being produced electrolytically at the cathode.
摘要:
A process for the production of alkali dichromates and chromic acid by electrolysis of alkali monochromate or alkali dichromate solutions wherein the anodes used in the electrolysis are dimensionally stable anodes of valve metals activated by electrodeposition of noble metals and/or noble compounds from melts containing noble metal salts.
摘要:
A process for the preparation of alkali metal dichromates and/or chromic acid by electrolysis of alkali metal monochromate and/or alkali metal dichromate solution in electrolysis cells, the anode and cathode compartments of which are separated by cation exchange membranes, wherein the cation exchange membranes are single-layer membranes based on perfluorinated polymers having sulfonic acid groups as cation exchange groups, and an aqueous solution having a pH of 4 to 14 is produced in the cathode compartment of the cells.