CN1070892A - The preparation method of sodium dichromate 99 - Google Patents
The preparation method of sodium dichromate 99 Download PDFInfo
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- CN1070892A CN1070892A CN 92111022 CN92111022A CN1070892A CN 1070892 A CN1070892 A CN 1070892A CN 92111022 CN92111022 CN 92111022 CN 92111022 A CN92111022 A CN 92111022A CN 1070892 A CN1070892 A CN 1070892A
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Abstract
The present invention relates to the preparation method of sodium dichromate 99.This law is under agitation to containing AlPO
4And CrPO
4The sodium pyrosulfate and the chromium acid sodium alkaline liquid that add wherein a kind of of sodium phosphate salt, phosphoric acid in the end liquid of kind simultaneously and polluted by chromium cpd, greater than 70 ℃ of temperature to boiling point in pH4-8 and acidifying.This law is crystalloid CrPO owing to what generate
4And AlPO
4Precipitation is easy to filter, and has all utilized the sodium pyrosulfate that is polluted by chromium cpd.Eliminated pollution, saved energy, simplified flow process and device environment.Its byproduct CrPO
4And AlPO
4Handle the raw material that just can be used as high temperature adhesive or rust-stabilising pigment a little.
Description
The present invention relates to a kind of production method of chromium cpd, more precisely a kind of preparation method of dichromate.
Chromic anhydride (chromium trioxide) sodium dichromate 99 and the vitriol oil react under the temperature about 206 ℃ to be produced.In the production process of chromic anhydride, the sodium pyrosulfate that is polluted by chromium cpd that generates is piled up as waste product, waits pending.Problem how to utilize this waste product to become the chemical research staff to be noted.
It is generally acknowledged that the sodium pyrosulfate that is polluted by chromium cpd that preferably will generate uses in the production of sodium dichromate 99 again and go in chromic anhydride production to good.
The fusion sodium pyrosulfate that is polluted by chromium cpd contains sulfuric acid 35-40%, sodium sulfate 45-50%, chromium trioxide 1.5-2.5%.Chromium sesquioxide 0.5-2.5%, major ingredient are Na3Cr(SO4) be weight percentage more than 3 the water-insoluble 9-10%().
In the past, the method of utilizing of the sodium pyrosulfate that is polluted by chromium cpd is, will be soluble in water by the fusion sodium pyrosulfate that chromium cpd pollutes, left standstill 24 hours, water-insoluble separates with the form of " sour mud ", and its clear liquor is used for the production of sodium dichromate 99, exactly clear liquor is directly replaced making the pH value of solution be about 7 with chromium acid sodium alkaline liquid in the sulfuric acid, said chromium acid sodium alkaline liquid is chromite and yellow soda ash, and after the filler roasting generated grog, grog was used the filtrate of water extraction after-filtration.Contain materials such as Sodium chromate, yellow soda ash, sodium hydroxide and sodium aluminate in the chromium acid sodium alkaline liquid.The shortcoming of this method is, in and chromium acid sodium alkaline liquid all sodium pyrosulfates that is polluted by chromium cpd that toos many or too much for use, still have residue.The sodium pyrosulfate that is polluted by chromium compounds of this remainder and all acid mud also need with discharging after ferrous sulfate and the lime treatment.Like this, a large amount of chromium resources (existing), acid number and sodium sulfate have not only been wasted with sexavalent chrome, tervalent form, and consume a large amount of ferrous sulfate and lime again, usually cause public hazards when dealing with improperly again, and use in the sodium pyrosulfate that is polluted by chromium cpd and during chromium acid sodium alkaline liquid, separate out " aluminium mud " (mixture of aluminium hydroxide-chromium hydroxide precipitation) again, aluminium mud is cotton-shaped, and filtration washing is all extremely difficult.
The another kind of method of utilizing the sodium pyrosulfate that is polluted by chromium cpd, also be with the fusion sodium pyrosulfate that is polluted by chromium cpd water-soluble after, the trivalent chromium in the clear liquor is oxidized to sexavalent chrome through electrolysis with it, be used for replacing in the sulfuric acid again and chromium acid sodium alkaline liquid.Though this method makes chromium obtain recycling, still can not be used up fully by the sodium pyrosulfate that chromium cpd pollutes, and in and during chromium acid sodium alkaline liquid, separated out the aluminium hydroxide flocks again.During electrolysis, current efficiency is low, and power consumption is high again.
Chinese patent literature CN1037495(EP340585) introduces a kind of method of producing sodium dichromate 99, also utilized the sodium pyrosulfate that is polluted by chromium cpd in the method.As processing method, use in the sulfuric acid and alkali solution in this processing method, remove by filter aluminium mud, its filtrate is neutral solution (Na2CrO4 solution) in the past.The sodium pyrosulfate thin up that will be polluted by chromium cpd also adds excessive phosphate radical, is used for the acidifying of neutral solution.Under the condition of 50-100 ℃ temperature and PH3-6, with the trivalent chromium in the neutral solution with the CrPO4(Plessy's green) form be precipitated out.After removing by filter Plessy's green, carry out acidifying with sulfuric acid again and form acidizing fluid (Na2Cr2D7), generate product sodium dichromate 99 and byproduct sulfite through evaporating, concentrating and crystallizing.The utilization ratio height of the sodium pyrosulfate that the advantage of this method is polluted by chromium cpd, but can only be applicable in advance and extremely sad filter be removed in the chromium acid sodium alkaline liquid neutralization with sulfuric acid, the acidifying of the neutral solution behind the aluminum hydroxide precipitation of extremely difficult washing, and need to increase the fusion sodium pyrosulfate that dissolving is polluted by chromium cpd, and with the operation of its dilution, increased the precipitated aluminium hydroxide precipitation again, washing aluminum hydroxide precipitation two procedures makes whole flow process complicated; Thin up has not only increased the steam output of preparation sodium dichromate solution, the dilution back form and the sour mud of accumulative also difficulty change into the crystalloid calcium phosphate precipitation.
Purpose of the present invention just is to work out a kind of production method of new sodium dichromate 99, produce in the method for sodium dichromate 99 at this, the sodium pyrosulfate that is polluted by chromium cpd is fully utilized, with in and two operations of acidifying of alkali solution and neutral solution be merged into an operation, make the technical process of producing sodium dichromate 99 shorten simplification more, what make on stream to be generated is precipitated as the crystalloid precipitation, is easier to filter, easy to operate, free from environmental pollution again.
The preparation method of a kind of sodium dichromate 99 of the present invention, comprise Sodium chromate and acid-respons, this acid comprise sulfuric acid and when producing chromium trioxide as the sodium pyrosulfate that is polluted by chromium cpd of waste product, under agitation in the end liquid that contains AlPO4 and CrPO4 crystal seed, add water miscible sodium phosphate salt simultaneously, phosphoric acid a kind of (as precipitation agent) wherein and sodium pyrosulfate and the chromium acid sodium alkaline liquid that is polluted by chromium cpd, greater than 70 ℃ (comprising 70 ℃) to the temperature of boiling point under the condition of PH4-8, in carrying out and acidifying, trivalent chromic ion is precipitated out with AlPO4 and CrPO4 crystalline form in the sodium pyrosulfate that pollutes with the trivalent aluminium in the alkali solution with by chromium cpd, filter, washing precipitation, its filtrate of acidifying and generate sodium dichromate 99 (Na2Cr2O7) solution (being acidizing fluid).
In the factory that produces sodium dichromate 99, with chromite and yellow soda ash, filler roasting ripe material, grog forms chromium acid sodium alkaline liquid with the water extraction after-filtration, this processing sequence is that those skilled in the art are known, the main component of chromium acid sodium alkaline liquid is that NaAlO2(is in Al2O3) the 0.2-3 grams per liter, sodium hydroxide and yellow soda ash are that total alkali (in yellow soda ash) is the 20-70 grams per liter, and Sodium chromate Na2CrO4(is in Na2Cr2O7.2H2O) be the 250-350 grams per liter.Processing method of the present invention does not have any restriction to the composition of alkali solution, and the grog that the chromite roasting becomes leaches the filtrate that and all is suitable for, but must not contain chromium slag (suspended substance), in order to avoid after carrying out acidification reaction, impurity such as silicon-dioxide are brought in the acidizing fluid.
In the production of chromic anhydride, contain sulfuric acid 35-40%(weight percentage in the formed sodium pyrosulfate that is polluted by chromium cpd, down together), sodium sulfate 45-50%, chromium trioxide 1.5-2.5%, chromium sesquioxide 0.5-2.5%, major ingredient are Na3Cr(SO4) 3 water-insoluble 9-10%.
Used precipitation agent is the sodium salt of phosphoric acid, water miscible phosphoric acid.Used phosphoric acid can be the phosphoric acid of various concentration, but with strong phosphoric acid for well.The sodium salt of used water miscible phosphoric acid is sodium phosphate, sodium hydrogen phosphate, SODIUM PHOSPHATE, MONOBASIC.The ammonium salt of water miscible phosphoric acid, sylvite etc. also can use, but its weak point is arranged.Because they have brought impurity potassium ion and ammonium ion into.Add the form of the sodium salt of water-soluble phosphoric acid, can its solid state join in the end liquid that contains AlPO4 and CrPO4 crystal seed, also can their form of solution of various concentration add, be incorporated as good with the form of its solution.Because the form adding with its solution is convenient to mix.Reinforced best order is that under agitation first sodium salt, phosphoric acid a kind of precipitation agent wherein with water-soluble phosphoric acid joins in the end liquid that contains AlPO4 and CrPO4 crystal seed in the end liquid that contains AlPO4 and CrPO4 crystal seed, behind the mixing, little by little add the sodium pyrosulfate and the chromium acid sodium alkaline liquid that are polluted by chromium cpd simultaneously.The speed that feeds intake is not too fast, and what restriction is the speed that stirs do not had, and the effect of stirring just mixes raw material.
Adding is as the amount of the sodium salt or the phosphoric acid of the water miscible phosphoric acid of precipitation agent, depend on the concentration of NaAlO2 in the chromium acid sodium alkaline liquid and the sodium pyrosulfate that polluted by chromium cpd in chromic content.The amount of the precipitation agent that adds generates the 70-150% of orthophosphoric acid salt AlPO4 and the required theoretical amount of CrPO4 for well for trivalent chromium in the sodium pyrosulfate that pollutes with the trivalent aluminium in the chromium acid sodium alkaline liquid with by chromium cpd.The amount that adds precipitation agent is crossed low amorphous hydroted alumina and chromium hydroxide and chromic acid chromium amorphous substances such as (trivalent chromium and the chromic compounds) precipitation that easily generates, be difficult for washing, also be difficult for to filter, so the amount of the precipitation agent that is added generates the 100-109.9% of orthophosphoric acid salt AlPO4 and the required theoretical amount of CrPO4 for better with trivalent chromium in the sodium pyrosulfate that pollutes with the trivalent aluminium in the Sodium chromate basic solution with by chromium cpd.
The sodium pyrosulfate that the waste product of producing at chromic anhydride (chromium trioxide) is polluted by chromium cpd is molten state when reactor flows out, can be directly used in the present invention.But to make sheet soluble in water, granular or powdery with pelleter or other devices for well.So in the end liquid that contains AlPO4 and CrPO4 crystal seed, adding sheet, sodium pyrosulfate granular or that powdered is polluted by chromium cpd are good.But the form of liquid state that also can its aqueous solution adds, and best dilute with water not is with the steam output in the operation minimizing after and avoid forming with phosphatase reaction and generate the filtering sour mud of difficulty.Certainly, in the time can't obtaining solid, clear liquor or suspension after also can using it water-soluble.
Stay the slurries of reaction container bottom as the end liquid that contains AlPO4.XH2O and CrPO4.YH2O crystal seed after primary first-order equation finishes before using in the preparation method of sodium dichromate 99 of the present invention, contain the different AlPO4 of many granularities and CrPO4 crystal and nucleus therein, as in carrying out and the good crystal seed during acidifying next time, help in and the stylish AlPO4 of acidifying and CrPO4 crystalline form and grow up, avoid and farthest reduce the sedimentary generation of amorphous substance.
In in processing method of the present invention, carrying out and the temperature during acidifying for greater than 70 ℃ (comprising 70 ℃) until boiling point, boil for good with little.The high more aluminum phosphate of temperature, Plessy's green percent crystallization in massecuite are high more, and temperature is lower than 70 ℃ excessively, and sedimentary percent crystallization in massecuite reduces, and will have more amorphous substance precipitation and generate, and Na3Cr(SO4) 3 to be converted into the speed of CrPO4 also slow excessively, is unfavorable for later filtration washing.
In in processing method of the present invention, carrying out and the pH value during acidifying to be 4-8(be≤0.9 corresponding to the acescency of chromatedsolution), be good with pH value 5-6 again.PH value is low excessively, is lower than PH4, and the solubleness of the orthophosphoric acid salt of aluminium and chromium increases; PH value is too high, is higher than 8, has subphosphate and generates, even unbodied oxyhydroxide or hydration chromic acid chromium precipitation occur, is difficult to filtration washing.
After material adds, should under stirring, carry out slaking 0.5-8 hour greater than 70 ℃ (comprising 70 ℃) to the temperature of boiling point, again with slaking 0.5-3 hour for well.Can make a spot of amorphous sediment be converted into aluminium, chromium orthophosphoric acid salt crystalline deposit like this, make micro crystal grow up into bigger coarse crystal again.The time of slaking, the longer the better, and the time of slaking is long more, and its sedimentary crystallization is good more, easy more filtration, and washing, chromic loss is more little.But the oversize plant factor that reduced of curing time.With about 90% slurries filtered while hot washing, it remained in the reaction vessel as in next time and the end liquid that contains crystal seed of acidification reaction after slaking finished.
Filtering method can adopt vacuum filtration, and centrifuging also can adopt the original aluminium mud of factory to filter the plate-and-frame filter press that uses.Its filtrate is the acidizing fluid of partial acidification.Its filter cake (being AlPO4 and CrPO4 precipitation) was pressed liquid-solid ratio 1: 1, with hot wash 2-3 time, chromic loss (in Na2CrO7.2H2O) was reduced to less than 1%.
Slurries through about 90% after the slaking, the filtrate of gained is the acidizing fluid of partial acidification after the filtered while hot.In the acidizing fluid of partial acidification, add sulfuric acid and further be acidified to acescency β to 1.01-1.03, form sodium dichromate 99 (Na2Cr2O7) solution product.The method of all knowing by the those of ordinary skill under this area generates the sodium dichromate solution evaporation concentration solid phase prod of sodium dichromate crystal (Na2Cr2O7.2H2O).The method of knowing altogether with those skilled in the art is reacted the sodium dichromate 99 and the vitriol oil under 206 ℃ temperature again, and the sodium pyrosulfate that generates chromic anhydride (chromium trioxide) and polluted by chromium cpd will be used for the neutralizing acid alkali solution by the sodium pyrosulfate that chromium cpd pollutes again by processing method of the present invention.
In processing method of the present invention the consumption of various raw materials normally, when the alkali solution consumption that contains Sodium chromate was 1000 weight unit, the amount that contains the end liquid of AlPO4 and CrPO4 nucleus was a 100-300 weight unit; When the amount of the alkali solution that contains Sodium chromate is 1000 weight unit, when making the acescency β value of alkali solution reach 0.58-0.9, solid is a 140-380 weight unit by the consumption of the sodium pyrosulfate that chromium cpd pollutes, and the consumption of phosphate radical is 0.8-22 weight unit or 1.1-30 weight unit of strong phosphoric acid (85%), and its weight unit can be gram, jin, a traditional unit of weight, kilogram, ton etc.
The advantage of processing method of the present invention just is:
1. the trivalent chromium in the sodium pyrosulfate that pollutes with the trivalent aluminium in the alkali solution with by chromium cpd in processing method of the present invention forms easy filtering AlPO4.XH2O and CrPO4.YH2O crystalloid precipitation simultaneously, avoided forming and contained a large amount of chromic waste residues-aluminium niobium and sour mud, all sexavalent chromes, trivalent chromium, acid number and sodium sulfate have been recycled all in the sodium pyrosulfate that is polluted by chromium cpd, public hazards have been eliminated, avoided pollution, had big economic benefit environment.
2. do not add water or add water as much as possible less in processing method of the present invention, dilute with water has not been reduced steam output by the sodium bisulfate that chromium cpd pollutes, and has saved energy.
3. processing method of the present invention does not have any restriction to the composition of alkali solution, and adaptability is strong.
4. processing method of the present invention two operations of pre-acidifying that will neutralize are merged into an operation, and the pre-acidifying that in same reaction vessel, neutralizes, aluminium mud and sour mud (or CrPO4.YH2O) are precipitated respectively, precipitation when changing AlPO4.XH2O and CrPO4.YH2O into, filtration washing in the lump, simplify technical process and device, saved facility investment.
5. X and Y are about 4 in AlPO4.XH2O that is generated in processing method of the present invention and the CrPO4.YH2O(formula) be that crystalloid precipitates, be easy to filter, wash, filtration velocity is fast, the sexavalent chrome loss is little, reduce to less than 1%, and AlPO4.XH2O and CrPO4.YH2O crystalloid precipitation are handled the raw material that just can be used as high temperature adhesive or rust-stabilising pigment a little.
With following embodiment processing method of the present invention is further described, will helps the understanding of the present invention and advantage thereof, and not as the qualification to protection domain of the present invention.Protection scope of the present invention is decided by claims.
Embodiment 1
The alkali solution that contains Sodium chromate contains 0.26 grams per liter alchlor, total alkali (in yellow soda ash) 21.4 grams per liters, Sodium chromate (in Na2Cr2O7.2H2O) 298.3 grams per liters.By sodium pyrosulfate clear liquor trioxygen-containingization two chromium 7.02 grams per liters that chromium cpd pollutes, sulfuric acid 361.1 grams per liters also contain sodium sulfate, and chromium trioxide, used phosphoric acid is for containing phosphoric acid 85%(weight percentage) strong phosphoric acid.
Sodium chromate-sodium dichromate solution of the PH5.5 of 205 weight unit of adding is (in Na2Cr2O7.2H2O in reaction vessel, its concentration is 300 grams per liters) as initial " end liquid ", under agitation in the most first " end liquid ", the phosphoric acid that little by little adds 23 weight unit simultaneously, the clear liquor that the sodium pyrosulfate that is polluted by chromium cpd of the alkali solution of 1000 weight unit and 255 weight unit is made is in the temperature of closely boiling is carried out under the condition of pH value 5.9 and acidifying.Behind reinforced the finishing, under agitation keep the temperature of closely boiling, slaking 1 hour.The suspension of gained is down the end liquid that contains AlPO4 and CrPO4 crystal seed that secondary response is used.If this suspension is vacuum filtration while hot, filtering velocity be 0.3 ton of slurries/square metre hour.The acidification rate of filtrate is 60.37%, filtrate PH5.80.
Embodiment 2
The used alkali solution that contains Sodium chromate is with embodiment 1, the solids sulfur acid 37.39%(weight percentage of the used sodium pyrosulfate that is polluted by chromium cpd, down together), chromium sesquioxide 1.65%, also contain sodium sulfate, chromium trioxide, water-insoluble, used concentration of phosphoric acid is 85%.
Add the end liquid that is generated among the embodiment 1 of 126 weight unit in reaction vessel after, the concentration that under agitation adds 3.2 weight unit is 85% phosphoric acid, mixes.Under agitation in end liquid, add the alkali solution of 630 weight unit and the solid state sodium pyrosulfate that is polluted by chromium cpd of 106 weight unit, in the temperature of closely boiling is carried out and acidifying under the condition of PH5.5 with time-division 6 times (each 5 minutes at interval).In the temperature slaking of closely boiling 1 hour, the slurries through about 90% after the slaking are negative pressure filtration while hot under constantly stirring, 1.5 tons of slurries of filtering velocity/square metre hour, by liquid-solid ratio usefulness hot wash in 1: 12 times.The end liquid that contains AlPO4 and CrPO4 crystal seed of usefulness is reacted in all the other filtering slurries conducts that do not have of about 10% next time.Contain sodium dichromate 99 Na2Cr2O7.2H2O 310.8 grams per liters in sodium dichromate 99 in the filtrate, acidification rate 67.6%, filtrate PH5.84,20.5 weight unit of wet cake.
With sulfuric acid filtrate further is acidified to acidification rate β to 1.02, makes Sodium chromate all change into sodium dichromate 99, the sodium dichromate solution evaporation concentration is generated sodium dichromate crystal.
Embodiment 3
Used alkali solution that contains Sodium chromate and the sodium pyrosulfate clear liquor that polluted by chromium cpd are with embodiment 1.
The end liquid that adds 126 weight unit in reaction vessel under agitation slowly adds simultaneously the mixed solution of 85% phosphoric acid of clear liquor that the sodium pyrosulfate that is polluted by chromium cpd of 163 weight unit makes and 1.45 weight unit and the alkali solution of 630 weight unit in end liquid.85 ℃ under the condition of PH7, carry out in and acidification reaction, under constantly stirring in 85 ℃ of thermalizations 3 hours, slurries through about 90% after the slaking are negative pressure filtration while hot, the slurries filtering velocity be 1.0 tons of slurries/square metre hour, filtrate PH6.90, contain sodium dichromate 99 Na2Cr2O7.2H2O 367.8 grams per liters, 15.5 weight unit of wet cake (comprising the crystal seed in the liquid of the former end).
Embodiment 4
Used alkali solution that contains Sodium chromate and phosphoric acid are with embodiment 1, and sulfur acid 37.39%(weight percentage in the used solid state sodium pyrosulfate that is polluted by chromium cpd is descended together), chromium sesquioxide 1.65% also contains sodium sulfate, chromium trioxide, water-insoluble.
After in reaction vessel, adding the end liquid that contains crystal seed of 227 weight unit, under agitation add 5 weight unit phosphoric acid, mix.The solid state sodium pyrosulfate that is polluted by chromium cpd of 167 weight unit is crushed to 1 millimeter.Under agitation simultaneously divide 6 times at leisure, join in the end liquid that contains crystal seed the alkali solution of 1000 weight unit and the solid state sodium pyrosulfate that is polluted by chromium cpd of 167 weight unit.In 95 ℃ temperature are carried out under the condition of PH about 5.8 and acidifying, slaking 1 hour under 95 ℃ temperature under constantly stirring, 90% slurries after slaking are negative pressure filtration while hot, the slurries filtering velocity be 1.67 tons of slurries/square metre hour, the acidification rate β of slurries is 67.6%, filtrate PH5.74.
Embodiment 5
Alkali solution, by the sodium pyrosulfate clear liquor that chromium cpd pollutes, phosphoric acid and their composition are with embodiment 1.
Its working method is substantially with embodiment 3, and the end liquid that only different is contains crystal seed is 225 weight unit, and alkali solution is 1000 weight unit, the clear liquor that the sodium pyrosulfate that 255 weight unit are polluted by chromium cpd is made.2.3 the strong phosphoric acid of individual weight unit.In under agitation carrying out under the condition in the temperature of closely boiling in PH5.7 and acidifying.Slaking 1 hour under the temperature of closely boiling under constantly stirring, 90% slurries after slaking are negative pressure filtration while hot, 1.0 tons of slurries of filtering velocity/square metre hour, the acidification rate β of filtrate is 58.41% filtrate PH5.81.
Embodiment 6
Present embodiment is the comparative example of embodiment 5.
Alkali solution, the composition and the phosphoric acid of the sodium pyrosulfate clear liquor that is polluted by chromium cpd, and their consumption, operational condition and embodiment 5 are identical, and only different is that working method is to have used the end liquid that does not contain crystal seed.During under agitation the mixed solution of sodium pyrosulfate that pollutes with alkali solution with by chromium cpd at leisure simultaneously and phosphoric acid joins and carries out in the end liquid that does not contain crystal seed and acidifying.Filtering velocity only be 0.16 ton of slurries/square metre hour.
Embodiment 7
Contain in the alkali solution of Sodium chromate and contain 0.28 grams per liter aluminium sesquioxide, total alkali (in yellow soda ash) 21.4 grams per liters, Sodium chromate (in Na2Cr2O7.2H2O) 309 grams per liters.By the solid state sodium pyrosulfate sulfur acid 35.74%(weight percentage that chromium cpd pollutes, together following), chromium sesquioxide 2.24% also has sodium sulfate, chromium trioxide, water-insoluble, used concentration of phosphoric acid is 85%.
Its working method is substantially with embodiment 4, the end liquid that only different is contains crystal seed is 220 weight unit, 6.6 the phosphoric acid of individual weight unit, the solid sulphuric acid hydrogen sodium that is polluted by chromium cpd of 179 weight unit, the alkali solution of 1000 weight unit, in 85 ℃ temperature are carried out under the condition of PH5.50 and acidification reaction, in 85 ℃ of slakings 4 hours, 90% slurries after slaking are negative pressure filtration while hot, filtering velocity be 1.31 tons of slurries/square metre hour, filtrate PH5.60, the acidification rate β of filtrate is 71.09%.
Real precedent 8
Alkali solution, the solid state sodium pyrosulfate that is polluted by chromium cpd and phosphoric acid are with embodiment 7.
Its working method is substantially with embodiment 7, the end liquid that only different is contains crystal seed is 220 weight unit, the phosphoric acid of 8 weight unit, the solid state sodium pyrosulfate that is polluted by chromium cpd of 223 weight unit, the alkali solution of 1000 weight unit, in carrying out under the condition in the temperature of closely boiling in PH5.30 and acidification reaction, in the slaking 1 hour of closely boiling, 90% slurries after slaking are negative pressure filtration while hot, filtering velocity be 1.22 tons of slurries/square metre hour, filtrate PH5.40, the acidification rate β of filtrate is 84.67%.
Real precedent 9
Alkali solution, the solid state sodium pyrosulfate that is polluted by chromium compounds and phosphoric acid are with embodiment 7.
Its working method is substantially with embodiment 7, the end liquid that only different is contains crystal seed is 126 weight unit, 4.2 the phosphoric acid of individual weight unit, the solid state sodium pyrosulfate that is polluted by chromium cpd of 113 weight unit, the alkali solution of 630 weight unit, in carrying out under the condition in the temperature of closely boiling in PH5.5 and acidification reaction, in the temperature slaking of closely boiling 1 hour.90% slurries after slaking are negative pressure filtration while hot.Filtering velocity be 1.22 tons of slurries/square metre hour, filtrate PH5.60, the acidification rate β of filtrate is 71.0%.
Claims (7)
1, a kind of preparation method of sodium dichromate 99 comprises Sodium chromate and acid-respons, when comprising sulfuric acid and produce chromium trioxide, this acid, it is characterized in that as the sodium pyrosulfate that is polluted by chromium cpd of waste product,
[1] under agitation in the end liquid that contains CrPO4 and AlPO4 crystal seed, add water miscible sodium phosphate salt, phosphoric acid a kind of (as precipitation agent) wherein and sodium pyrosulfate and the chromium acid sodium alkaline liquid that is polluted by chromium cpd simultaneously,
[2] under the condition of pH4-8, carrying out and acidifying greater than 70 ℃ (comprising 70 ℃) to the temperature of boiling point,
[3] trivalent chromic ion in the sodium pyrosulfate that pollutes with the trivalent aluminium in the alkali solution with by chromium cpd is with the form precipitation of CrPO4-AlPO4,
[4] filter washing precipitation, its filtrate of acidifying.
2, according to the preparation method of a kind of sodium dichromate 99 of claim 1, it is characterized in that, under agitation earlier with water miscible sodium phosphate salt, phosphoric acid a kind of precipitation agent wherein, join in the end liquid that contains CrPO4 and AlPO4 crystal seed, behind the mixing, little by little add the sodium pyrosulfate and the chromium acid sodium alkaline liquid that are polluted by chromium cpd simultaneously.
3, according to the preparation method of a kind of sodium dichromate 99 of claim 1, it is characterized in that the amount that adds precipitation agent generates the 70-150% of CrPO4 and the required theoretical amount of AlPO4 for trivalent chromium in the sodium pyrosulfate that pollutes with the trivalent aluminium in the chromium acid sodium alkaline liquid with by chromium cpd.
4, according to the preparation method of a kind of sodium dichromate 99 of claim 3, it is characterized in that the amount that adds precipitation agent generates the 100-109.9% of CrPO4 and the required reason of the AlPO4 amount of sinking for trivalent chromium in the sodium pyrosulfate that pollutes with the trivalent aluminium in the chromium acid sodium alkaline liquid with by chromium cpd.
5, according to the preparation method of a kind of sodium dichromate 99 of claim 1, it is characterized in that, in carrying out and the PH during acidifying be 5-6.
6, according to the preparation method of a kind of sodium dichromate 99 of claim 1, it is characterized in that,, under stirring, carried out slaking 0.5-8 hour greater than 70 ℃ (comprising 70 ℃) temperature to boiling point.
7, according to the preparation method of a kind of sodium dichromate 99 of claim 6, it is characterized in that,, under stirring, carried out slaking 0.5-3 hour greater than 70 ℃ (comprising 70 ℃) temperature to boiling point.
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| CN 92111022 CN1037259C (en) | 1992-09-28 | 1992-09-28 | Made method of sodium dichromate |
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| CN 92111022 CN1037259C (en) | 1992-09-28 | 1992-09-28 | Made method of sodium dichromate |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102143913A (en) * | 2008-09-05 | 2011-08-03 | 日本化学工业株式会社 | Chromium(iii)-containing aqueous solution and process for production of same |
| CN102320685A (en) * | 2011-05-31 | 2012-01-18 | 重庆民丰化工有限责任公司 | Processing method of sodium bisulfate waste liquid in chromic anhydride preparation process |
| CN102897838A (en) * | 2012-11-19 | 2013-01-30 | 四川省安县银河建化（集团）有限公司 | One-step preparation method of sodium bichromate |
| CN114752766A (en) * | 2021-07-30 | 2022-07-15 | 中南大学 | Method for selectively separating zinc, chromium and iron and recovering multiple metals in electroplating sludge |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101892490A (en) * | 2010-06-24 | 2010-11-24 | 中国科学院青海盐湖研究所 | Method for continuously preparing sodium dichromate by ionic membrane electrolysis |
-
1992
- 1992-09-28 CN CN 92111022 patent/CN1037259C/en not_active Expired - Fee Related
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102143913A (en) * | 2008-09-05 | 2011-08-03 | 日本化学工业株式会社 | Chromium(iii)-containing aqueous solution and process for production of same |
| CN102320685A (en) * | 2011-05-31 | 2012-01-18 | 重庆民丰化工有限责任公司 | Processing method of sodium bisulfate waste liquid in chromic anhydride preparation process |
| CN102897838A (en) * | 2012-11-19 | 2013-01-30 | 四川省安县银河建化（集团）有限公司 | One-step preparation method of sodium bichromate |
| CN102897838B (en) * | 2012-11-19 | 2014-12-10 | 四川省银河化学股份有限公司 | One-step preparation method of sodium bichromate |
| CN114752766A (en) * | 2021-07-30 | 2022-07-15 | 中南大学 | Method for selectively separating zinc, chromium and iron and recovering multiple metals in electroplating sludge |
Also Published As
| Publication number | Publication date |
|---|---|
| CN1037259C (en) | 1998-02-04 |
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