CN1233876C - Solid potassium ferrate preparing method - Google Patents

Solid potassium ferrate preparing method Download PDF

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CN1233876C
CN1233876C CN 03126342 CN03126342A CN1233876C CN 1233876 C CN1233876 C CN 1233876C CN 03126342 CN03126342 CN 03126342 CN 03126342 A CN03126342 A CN 03126342A CN 1233876 C CN1233876 C CN 1233876C
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anolyte
potassium ferrate
solid potassium
koh
described process
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CN1488782A (en
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杨长春
高杰
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Zhengzhou University
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Zhengzhou University
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Abstract

The present invention provides a method for preparing solid K2FeO4 without using any chemical oxidizing agent, namely using a diaphragm electrolytic cell to directly prepare an electrode containing ferrous materials into solid K2FeO4 of which the purity is higher than 90 wt% by one step of anode oxidation in a KOH solution containing a stabilizing agent by direct current electrolysis. The solid K2FeO4 prepared by the method is suitable for serving as a treating agent for sewage or drinking water and an oxidant for organic synthesis; after being purified, the solid K2FeO4 can also be used as an anode active substance of an alkaline ferrate cell. The method of the present invention has the advantages of continuous operation, cyclical use of electrolyte, high efficiency, low cost and no pollution.

Description

Process for preparing solid potassium ferrate
Affiliated technical field
The invention belongs to the technology of preparing of ferrate, be specifically related to solid potassium ferrate (K 2FeO 4) the preparation method.
Background technology
Ferrate with strong oxidizing property is subjected to people with its unique environmental friendliness characteristic and more and more payes attention to.It does not have " three cause " danger of chlorine-containing disinfectant as the treatment agent of sewage and tap water; It does not have the secondary pollution that permanganate or dichromate reduzate bring as the organic synthesis oxygenant; It not only has environmental friendliness, resourceful advantage as the alkaline cell anode active substance, and voltage height, capacity are big.Yet, still there is not a kind of preparation technology that can both be suitable for suitability for industrialized production from aspects such as economy, scale, product forms at present, this present situation has been slowed down the application process of ferrate in every field.
Na 2FeO 4And K 2FeO 4Be two kinds of ferrates the most basic, mostly the ferrate of other metal is to make through replacement(metathesis)reaction from these two kinds of ferrates.The Na that is reported at present 2FeO 4And K 2FeO 4The preparation method can be divided three classes basically.The one, high-temperature oxidation is the aqueous solution chlorination method in addition, is electrolytic oxidation again.
High-temperature oxidation is a method of finding that the earliest ferrate is used, and the mixture that is about to contain caustic alkali, base metal nitrate, ferric oxide or molysite heats under hot conditions, and the oxynitride that utilizes nitrate to be decomposed to form generates ferrate with the iron oxidation.The US4545974 patent proposes a kind of rhombohedral iron ore, magnetite or those can at high temperature to be decomposed into the iron cpd of ferric oxide, after alkali-metal nitrate mixes, is heated to 780-1100 ℃ in vacuum or inert atmosphere, prepares the method for ferrate.US4551326, US4385045 propose a kind of mixture heating up that will be made up of alkali-metal oxide compound, alkali metal peroxide, molysite or metal iron powder to 500-650 ℃ under vacuum anaerobic or inert atmosphere, prepare the method for ferrate.Though high-temperature oxidation can directly obtain solid-state product, the mixture that this solid product is made up of multiple material, wherein the content of ferrate is very low, and is the mixture of quadrivalent iron hydrochlorate and sexavalence wustite.The temperature height that requires of high-temperature oxidation in addition, energy expenditure is big, and equipment corrosion is serious, so in fact also seldom use on laboratory scale.
The strong oxidizer of aqueous solution chlorination method utilization in strong alkali solution is oxidized to ferrate with the oxide compound of molysite or iron.These strong oxidizers comprise hypohalite and peroxysulphate.US4405573 proposes a kind ofly to feed chlorine in containing the alkali-metal KOH solution that contains iodine compound, alkali-metal silicon-containing compound, with the KClO of generation the oxyhydroxide of molysite or iron is oxidized to K 2FeO 4Method.US5217584 and US5202108 propose a kind ofly containing alkali-metal containing in iodine compound, the alkali-metal solution that contains tellurium compound, alkali metal hydroxide with hypohalite solution high-purity beta-Fe 2O 3Be oxidized to the method for ferrate.And require β-Fe 2O 3In inorganic and content organic impurity be not more than 3000ppm.The US5746994 proposition is a kind of to contain KOH, K 2SO 4, KHSO 4Solution under condition of ice bath, use KHSO 5With Fe 2(SO 4) 3Or Fe (NO 3) 3Be oxidized to K 2FeO 4Method.
Because Na 2FeO 4Solubleness in NaOH solution is much larger than K 2FeO 4Solubleness in KOH solution.Be to improve the utilization ratio of oxygenant and the yield of ferrate, be used to prepare Na as the aqueous solution chlorination fado of oxygenant based on hypochlorite 2FeO 4Solution, nonetheless made Na 2FeO 4The concentration of solution is many less than 0.2M.This is because the ratio of available chlorine only is about 13% in the used hypochlorite alkaline solution, and hypochlorite and potassium ferrate instability.The Fe (OH) that hypochlorite and ferrate also exist in decomposition and system when hypochlorite oxidation molysite generates ferrate 3Decomposition to the ferrate that generated in the solution has katalysis, so the utilization ratio of hypochlorite is very low in the entire reaction course.The preparation of hypochlorite and decomposition all relate to Cl 2Existence, can worsen the Working environment for preparing ferrate by hypochlorite.US5284642 proposes a kind of FeSO that passes through 4.7H 2O, KOH, Ca (ClO) 2It is M (Fe, X) O that the solid state reaction that is taken place after three kinds of solids mix prepares molecular formula 4Basic metal, the method for alkaline-earth metal ferrate mixture.Though this method products made thereby is a solid form, wherein the content of ferrate is not high.
Using diaphragm electrolytic cell, the metallic iron electrode is generated ferrate with the direct current electrolytic oxidation in caustic solution, is the ultimate principle of electrolytic oxidation.It is catholyte with diaphragm sell with NaOH solution that US4435257 proposes a kind of, is anolyte with the NaOH solution that contains NaCl, with direct current the ferric iron in metallic iron anode or the anolyte is oxidized to Na 2FeO 4The method of solution.The barrier film slot type electrolyzer preparation that CN97116358.8 proposes the multipole parallel connection of a kind of usefulness contains Na 2FeO 4And Al 2O 3The method of compound high iron aluminium water treatment flocculant.US4435256 proposes a kind of prepared Na of electrolytic process that utilizes 2FeO 4Solution prepares K 2FeO 1The solid method.US4451338 proposes a kind of prepared Na of electrolytic process that utilizes 2FeO 4Solution and Ca (OH) 2Prepared in reaction Na 2FeO 4And CaFeO 4The method of mixture.The characteristics of electrolytic process are, it is the side reaction that way is avoided of still not having at present that generates parallel existence with the high ferro acid group that anode is analysed oxygen, and this side reaction reduces the anodic current efficiency that generates the high ferro acid group.The anode formation reaction of high ferro acid group is to carry out in the transpassivation potential range of the ferroelectric utmost point, and the iron anode surface is along with electrolytic process passivation aggravation causes anodic current efficiency to reduce gradually.The raising of anode real current density can aggravate the anodic passivation, carries out under low anodic current density so electrolysis is many.Na 2FeO 4Decomposition also accelerate with the rising of ferric katalysis and electric liquid temp in the rising of himself concentration and the solution.So made Na of electrolytic process 2FeO 4The concentration of solution is generally less than 0.4M.
CN97116359.6 proposes a kind of made ClO of electrolytic saltwater that utilizes 2Be the trivalent iron salt in the oxygenant oxidation NaOH solution, preparation Na 2FeO 4, K 2FeO 4The method of compound oxidizing flocculant.CN01106769.1 proposes a kind of made Cl of on-the-spot electrolytic saltwater that utilizes 2Trivalent iron salt in the oxidation NaOH solution prepares Na 2FeO 4The method of solution.
With hypochlorite oxidation style and the made Na of direct current solution 2FeO 4The concentration of solution is lower, the Na of this lower concentration 2FeO 4Solution because NaOH concentration is higher, directly is restricted as the water body treatment agent on the one hand, on the other hand because Na 2FeO 4The solution instability can't use the method for heating evaporation to concentrate.Normally with Na 2FeO 4With KOH replacement(metathesis)reaction taking place, changes K into 2FeO 4Solid is separated out.So not only operation increases, the yield of high ferro acid group reduces, and more seriously produces a large amount of KOH, NaOH mixed ammonium/alkali solutions, and this mixed ammonium/alkali solutions can't circulate and is used for Na 2FeO 4The preparatory phase of solution, otherwise can reduce the utilization ratio of hypochlorite or electric current.For overcoming this present situation, report that recently a kind of KOH of utilization, NaOH mixed ammonium/alkali solutions come the electrolysis iron anode directly to prepare solid K as anolyte 2FeO 4Method (Electrochemistry.Communication, 4,2002,764-766), yet this article is not revealed on the one hand detailed processing parameter, prepared on the other hand solid K 2FeO 4Purity and current efficiency all lower.
Summary of the invention
The purpose of this invention is to provide a kind of need and after the step, can directly from anode electrolytic cell liquid, isolate K through electrolysis 2FeO 4The solid method, thus can under the chemical oxidizing agent condition, prepare solid K 2FeO 4, and can realize that continuous production, electrolytic solution can be recycled, do not produce any by product that may contaminate environment in the production process.
The object of the present invention is achieved like this:
A. use chamber, the two poles of the earth diaphragm electrolytic cell, as anode, as negative electrode, place anolyte compartment and cathode compartment respectively with nickel foam or nickel plate or iron plate with iron-bearing materials with electron conduction;
B. being anolyte with the dense KOH solution that contains additive, is catholyte with dense KOH solution, carry out using the direct current electrolysis under the violent stirring condition at antianode liquid, and in electrolytic process to add KOH with the suitable amount anode of used electric current chamber;
C. the solid state electrolysis product that generates in the anolyte is separated from anolyte,, promptly made the solid potassium ferrate that purity is 90-95wt% through dehydration, dealkalize, drying.
Purpose of the present invention can also realize like this:
A. use chamber, the two poles of the earth diaphragm electrolytic cell, as anode, as negative electrode, place anolyte compartment and cathode compartment respectively with nickel foam or nickel plate or iron plate with iron-bearing materials with electron conduction;
B. being anolyte with the dense KOH solution that contains additive, is catholyte with dense KOH solution, carry out using the direct current electrolysis under the violent stirring condition at antianode liquid, and in electrolytic process with the suitable amount anode of used electric current liquid in add KOH;
C. the solid state electrolysis product that generates in the anolyte is separated from anolyte, being dissolved in concentration again is in the NaOH solution of 7-10M, and this solution and saturated KOH solution are replaced suction filtration in the saturated KOH solution that contains the potassium ferrate crystal seed;
D. the K that will obtain through suction filtration 2FeO 4Solid again through dehydration, dealkalize, drying, promptly makes the solid potassium ferrate that purity is 95-98%.
Compared with prior art, the invention has the advantages that:
1, solid K 2FeO 4Only one step of need electrolysis can generate, production process is few, spatiotemporal efficiency is higher.Compare with the electrolytic process that with pure NaOH is anolyte, the present invention can directly obtain solid K 2FeO 4Thereby, avoided by Na 2FeO 4Solution precipitation separate solid K 2FeO 4Step.Compare with the electrolytic process that with NaOH, KOH mixed solution is electrolytic solution, the present invention can work under comparatively high temps, Fe in the made solid product (OH) 3Content lower.
2, can realize closed cycle zero release production, not produce the by product of any possibility contaminate environment.
3, processing parameter is realized stable control, the homogeneity that helps improving the quality of products easily.
Embodiment
Used electrolyzer forms with polyvinyl-chloride plate material or methacrylate sheet bonding, and the volumetric ratio of anolyte compartment and cathode compartment is 1: 3-3: 1.Employed barrier film is a kind of in polyvinyl microporous membrane, polyvinyl ionic membrane, perfluor microporous membrane, the perfluorinated ionic membrane.
The iron-bearing materials that has an electron conduction as anodic is meant a kind of in common iron net, iron plate, iron filings, the magnetite.Chemical constitution to iron net, iron plate, iron filings is not done particular requirement.Magnetite is the natural magnet breeze after magnetic separation, the pickling, through adding CaO, K 2O, Al 2O 3, Co 2O 3, CeO, V 2O 5In more than one after, the magnetite powder that forms through fusion or the whole block magnetite of moulding wherein add components contents and are respectively CaO 0.5-1.2wt%, K again 2O 0.5-2.2wt%, Al 2O 31.5-4.2wt%, Co 2O 30.5-1.5wt%, CeO 0.5-1.5wt%, V 2O 50.5-1.0wt%.With iron filings and magnetite powder during, need these powder to be fixed on iron plate or iron net surface as the anode current collector body, and allow the powder face towards negative electrode with magnet as anode.For improving the anodic electron conduction, when being anode, preferably be made into block type electrode with iron filings or magnetite powder.The metallic iron anode only needs oil removing, scale removal before electrolysis, the magnetite anode needs to handle 5-15 minute with the current cathode polarization of 20～50mA before electrolysis.
Used catholyte is that concentration is the KOH solution of 10-13M; Anolyte is the KOH aqueous solution that contains additive, and the concentration of KOH is 10-13M in the anolyte, and content of additive is 1-50ml/LKOH in the anolyte.
Additive therefor is to contain CuCl simultaneously 2, KIO 3, Na 2SiO 3, KI KOH or the NaOH aqueous solution, wherein CuCl 2Concentration range be 0.005-0.05M; KIO 3Concentration range be 0.005-0.05M; Na 2SiO 3Concentration range be 0.02-0.8M; The concentration range of KI is 0.001-0.1M; The concentration range of KOH or NaOH is 2-5M.
The apparent current density of the continuous current that uses is 1.0-10.0 peace/square decimeter during the direct current electrolysis, and the allowed band that bath voltage changes in the electrolytic process is 2-10V, and the optimum controling range of bath voltage is 3-6V.The temperature controlling range of electrolytic solution is 10-80 ℃ in the electrolytic process, and optimum temperature range is 30-70 ℃.
Along with solid K is constantly arranged in the anolyte 2FeO 4Separate out, and have anode to analyse the existence of oxygen side reaction simultaneously, these two reactions all consume hydroxide radical, and the alkali concn in the anolyte is decreased.No matter be K 2FeO 4Solution or solid K 2FeO 4Decomposition rate in low alkalinity solutions is all greater than high alkalinity solutions.So generate K in order to prevent 2FeO 4Decomposition, and keep the concentration of KOH in the anolyte, after electrolysis is carried out 2 hours, should be interrupted or add KOH in the anode chamber continuously, the ratio of selected electric current is when the additional amount of KOH and electrolysis: 0.01-0.05mol KOH:1A electric current per hour.The KOH that the anode chamber is added also can directly be added in and isolate solid K 2FeO 4After in the anolyte that recycles.
The present invention can move in a continuous manner, continues under the electrolytic condition, and the mean residence time of solid state electrolysis product in anolyte in the anolyte is 3-8 hour, and most optimal retention time is 4-6 hour, that is to say that anolyte is 4-6 hour planted agent's recycling replacing one time.Solid state electrolysis product in the anolyte can be step negative pressure leaching or centrifugation with separating of anolyte, also can be the negative pressure leaching or the centrifugation of discharging continuously.
Isolated solid state electrolysis product from anolyte is only handled through dehydration, dealkalize, without any purification step, and in the gained solids, K 2FeO 4Content be no less than 90wt%, Fe (OH) 3Content be not more than 10-20wt%, the content of water is not more than 10-20%.Dewatering agent is a kind of in hexanaphthene, dimethylbenzene, the Skellysolve A, and the dealkalize agent is a dehydrated alcohol, the methyl alcohol more than 96%, a kind of in the 96% above acetone.The gained solids must drying be handled, and the content of water is reduced to below the 1%wt, could preserve medium-term and long-term placement of encloses container.The method of drying treatment is to place the capacity siccative (as block CaCl in vacuum drying oven 2, solid NaOH etc.), first normal temperature drying under reduced pressure makes in the solids content of water reduce to about 5wt%, and the post-heating drying under reduced pressure, the temperature of heating should be less than 80 ℃.K in the primary drying sample 2FeO 4Content greater than 90wt%.
Isolated solid state electrolysis product can purified processing obtain the above solid K of purity 95%wt from anolyte 2FeO 4The program of purification process is: will be dissolved in the NaOH solution that concentration is 7-10M by isolated solid state electrolysis product from anolyte earlier; This solution and saturated KOH solution are replaced suction filtration in the saturated KOH solution that contains the potassium ferrate crystal seed; Filter flask should place temperature not to be higher than 30 ℃ water-bath, and suction filtration was finished in 20-40 minute.With the K that generates in the filter flask 2FeO 4Solid with aforementioned same method dehydration, dealkalize, drying, promptly makes the solid potassium ferrate that purity is 95-98% after suction filtration or centrifugation.If need further to improve purity, can repeatedly repeat this purge process.
Isolate the anolyte behind the solid state electrolysis product, through adjusting the concentration of KOH, and after adding additive, can return the anolyte compartment and recycle.
Embodiment 1:
With the square diaphragm sell of PVC, the volume of anolyte compartment is 10 * 10 * 5cm 3, the volume of cathode compartment is 10 * 10 * 2cm 3, barrier film is that useful area is 7 * 12cm 2The perfluor cationic membrane.Anode is that 32 layers of effective apparent area are 40cm 2The common braiding iron of 30 orders net (the iron wire diameter d=0.14mm), negative electrode is that effective apparent area is 40cm 2Nickel foam.The anolyte volume is 200ml, and the catholyte volume is 100ml.Anolyte and catholyte all are the KOH solution of 13M.Add 2.5ml annex solution, CuCl in the annex solution in the anolyte 2, KIO 3, Na 2SiO 3, KI, KOH concentration respectively 0.015M, 0.015M, 0.3M, 0.015M, 5M.Electrolyzer places constant temperature water bath, and initial temperature is 60 ℃, and temperature-stable was at 65 ℃ after the feeding electric current was made an appointment with half an hour.Carry out vigorous stirring with electric mixer antianode liquid, 3A electric current constant-current electrolysis 6 hours, the bath voltage variation range is 2-3V.Carried out 2 hours from electrolysis, add 1 gram solid KOH per half an hour in the anode liquid.After finishing, electrolysis place cold water to be cooled to room temperature the electrolyzer taking-up.Take out anolyte, through the sand core funnel decompress filter, hexanaphthene flushing 3 times, dehydrated alcohol flushing 6 times, in a conventional oven 70 ℃ down after dry 8 hours, K 2FeO 4Solid 10.6 grams, surveying its purity with chromate process is 95%, current efficiency 45.4%.
Embodiment 2:
To be 95% K by the prepared purity of embodiment 1 described method 2FeO 4Solid 20 gram is dissolved under condition of ice bath in 200 milliliters, the NaOH solution of 7M, and behind the sand core funnel decompress filter, the concentration of measuring high ferro acid group in the filtrate with chromate process is 0.47M.Successively 20mL filtrate and the saturated KOH of 10mL are mixed in same filter flask through sand core funnel under condition of ice bath, reaction 2～3min makes and contains solid K 2FeO 4The mother liquor of crystal seed.Under the magnetic agitation condition, speed with 5～8mL/min and 2.5～4mL/min alternately adds last 180mL filtrate and the saturated KOH solution of 90mL in this filter flask respectively, keep solution temperature less than 20 ℃, whole reinforced process is finished in 20～30min, continues to stir 5min afterwards.With reaction gained K in the filter flask 2FeO 4Become filter cake through the sand core funnel decompress filter, residual K in the mother liquor 2FeO 4Concentration be 0.01M, under vacuum pump unlatching situation, divide earlier and wash K 5 times with the 20mL hexanaphthene 2FeO 4Filter cake is to remove water wherein; Divide dissolving flushing alkali and Fe (OH) wherein 10 times with 40～50mL methyl alcohol again 3, divide the residual methyl alcohol of flushing 4 times with the 15mL ether at last.Gained K 2FeO 4Solid after 8 hours, is weighed as 18.3 grams through 70 ℃ of oven dry, and surveying its purity with chromate process is 97.6%.
Embodiment 3:
With the square diaphragm sell of PVC, the volume of anolyte compartment is 10 * 10 * 5cm 3, the volume of cathode compartment is 10 * 10 * 2cm 3Barrier film is that useful area is 7 * 12cm 2The perfluor anionic membrane.Anode is that 32 layers of effective apparent area are 40cm 2The common braiding iron of 30 orders net (the iron wire diameter d=0.14mm), negative electrode is that effective apparent area is 40cm 2Nickel foam.The anolyte volume is 200ml, and the catholyte volume is 100ml.Anolyte and catholyte all are the KOH solution of 13M.Add 2.5ml annex solution, CuCl in the annex solution in the anolyte 2, KIO 3, Na 2SiO 3, KI, KOH concentration respectively 0.015M, 0.015M, 0.3M, 0.015M, 5M.Electrolyzer places water bath with thermostatic control, and initial temperature is 60 ℃, and temperature-stable was at 66 ℃ after the feeding electric current was made an appointment with half an hour.Carry out vigorous stirring with electric mixer antianode liquid, 3A electric current constant-current electrolysis 6 hours, the bath voltage variation range is 2.5-3.5V.Carried out 2 hours from electrolysis, add 1 gram solid KOH per half an hour in the anode liquid.After finishing, electrolysis place cold water to be cooled to room temperature the electrolyzer taking-up.Take out anolyte, through the sand core funnel decompress filter, dimethylbenzene flushing 3 times, washed with methanol 6 times, ether flushing 3 times, in a conventional oven 70 ℃ down after dry 8 hours, solid 9.7 grams, be 94.2% with purity that chromate process is surveyed, current efficiency 41.2%.
Embodiment 4:
With the square diaphragm sell of PVC, the volume of anolyte compartment is 10 * 10 * 5cm 3, the volume of cathode compartment is 10 * 10 * 2cm 3Barrier film is that useful area is 7 * 12cm 2Heterogeneous polyethylenes base anionic membrane.Anode is that 32 layers of effective apparent area are 40cm 2The common braiding iron of 30 orders net (the iron wire diameter d=0.14mm), negative electrode is that effective apparent area is 40cm 2Nickel foam.The anolyte volume is 200ml, and the catholyte volume is 100ml.Anolyte and catholyte all are the KOH solution of 13M.Add 2.5ml annex solution, CuCl in the annex solution in the anolyte 2, KIO 3, Na 2SiO 3, KI, KOH concentration respectively 0.015M, 0.015M, 0.3M, 0.015M, 5M.Electrolyzer places water bath with thermostatic control, and initial temperature is 60 ℃, and temperature-stable was at 66 ℃ after the feeding electric current was made an appointment with half an hour.Carry out vigorous stirring with electric mixer antianode liquid, 3A electric current constant-current electrolysis 6 hours, the bath voltage variation range is 2.5-3.5V.Carried out 2 hours from electrolysis, per half an hour, 1 gram solid KOH was added in the anode chamber.After finishing, electrolysis place cold water to be cooled to room temperature the electrolyzer taking-up.Take out anolyte, through the sand core funnel decompress filter, dimethylbenzene flushing 3 times, washed with methanol 6 times, ether flushing 3 times, in a conventional oven 70 ℃ down after dry 8 hours, solid 9.8 grams, surveying its purity with chromate process is 92.8%, current efficiency 41.1%.
Embodiment 5:
The anode filtrate of embodiment 4 is taken out, behind adding 15 gram solid KOHs and the 2.5ml annex solution, be settled to 200ml and add the anolyte compartment as anolyte.CuCl in the annex solution 2, KIO 3, Na 2SiO 3, KI, KOH concentration respectively 0.015M, 0.015M, 0.3M, 0.015M, 5M.Catholyte still is 100ml 13MKOH.Still use embodiment 4 used and anode, negative electrode, electrolyzer that do not do any processing to carry out electrolysis.The anolyte initial temperature is 60 ℃, and temperature-stable was at 65 ℃ after the feeding electric current was made an appointment with half an hour.Carry out vigorous stirring with electric mixer antianode liquid, 3A electric current constant-current electrolysis 6 hours, the bath voltage variation range is 2-3V.Carried out 2 hours from electrolysis, add 1 gram solid KOH per half an hour in the anode liquid.After finishing, electrolysis place cold water to be cooled to room temperature the electrolyzer taking-up.Take out anolyte, through the sand core funnel decompress filter, hexanaphthene flushing 3 times, dehydrated alcohol flushing 6 times, in a conventional oven 70 ℃ down after dry 8 hours, solid 10.2 grams, surveying its purity with chromate process is 94.3%, current efficiency 43.4%.
Embodiment 6
With the square diaphragm sell of synthetic glass, the volume of anolyte compartment is 8 * 5.3 * 7.5cm 3, the volume of cathode compartment is 3.3 * 5.3 * 7.5cm 3, barrier film is that useful area is 4 * 5cm 2The perfluor cationic membrane.Anode is block magnetite, and its apparent area is 30cm 2Anodic making processes is: take by weighing natural magnet breeze, 4.5g KNO after 200g magnetic separation, the pickling 3, 3.0g CaCO 3, 3.5g Al 2O 3Mix the back and in plumbago crucible, be melt into bulk, excision forming thereafter with alternating current arc.Negative electrode is that its apparent area of nickel foam is 30cm 2The anolyte volume is 150ml, and the catholyte volume is 110ml.Anolyte and catholyte all are the KOH solution of 13M.Add 1.5ml annex solution, CuCl in the annex solution in the anolyte 2, KIO 3, Na 2SiO 3, KI, KOH concentration respectively 0.015M, 0.015M, 0.3M, 0.015M, 5M.Electrolyzer places constant temperature water bath.Antianode carries out 20 minutes cathodic polarization pre-treatment before the electrolysis with the electric current of 0.5A.The initial temperature of electrolytic solution is 60 ℃, and temperature-stable was at 62 ℃ after the feeding electric current was made an appointment with half an hour.Carry out vigorous stirring with electric mixer antianode liquid, 0.5A electric current constant-current electrolysis 6 hours, the bath voltage variation range is 2.6-3.9V.After finishing, electrolysis place cold water to be cooled to room temperature the electrolyzer taking-up.Take out anolyte, the sand core funnel decompress filter, hexanaphthene flushing 3 times, dehydrated alcohol flushing 6 times, in a conventional oven 70 ℃ down after dry 8 hours, obtain solid 2.5 grams, surveying its purity with chromate process is 92.4%, current efficiency 34.8%.
Embodiment 7
With the square diaphragm sell of synthetic glass, the volume of anolyte compartment is 8 * 5.3 * 7.5cm 3, the volume of cathode compartment is 3.3 * 5.3 * 7.5cm 3, barrier film is that useful area is 4 * 5cm 2The perfluor cationic membrane.Anode collector is the common iron plate of 40 * 90 * 0.8mm, and anode is that diameter d=0.14mm, length are the iron wire bits (the iron wire bits that above-mentioned braiding iron net is cut into after breaking) about 1cm.With 4 * 7 * 1cm ndfeb magnet sorption after handling through insulation simultaneously in anode collector.Take by weighing 20g iron wire bits and its even shakedown is overlying on anode collector another side 4 * 7cm 2The zone in.Negative electrode is that its apparent area of nickel foam is 30cm 2The anolyte volume is 150ml, and the catholyte volume is 110ml.Anolyte and catholyte all are the KOH solution of 13M.Add 1.5ml annex solution, CuCl in the annex solution in the anolyte 2, KIO 3, Na 2SiO 3, KI, KOH concentration respectively 0.015M, 0.015M, 0.3M, 0.015M, 5M.Electrolyzer places constant temperature water bath.The initial temperature of electrolytic solution is 60 ℃, and temperature-stable was at 63 ℃ after the feeding electric current was made an appointment with half an hour.Carry out vigorous stirring with electric mixer antianode liquid, 1A electric current constant-current electrolysis 6 hours, the bath voltage variation range is 2.6-4.5V.After finishing, electrolysis place cold water to be cooled to room temperature the electrolyzer taking-up.Take out anolyte, the sand core funnel decompress filter, hexanaphthene flushing 3 times, dehydrated alcohol flushing 6 times, in a conventional oven 70 ℃ down after dry 8 hours, obtain solid 3.2 grams, surveying its purity with chromate process is 93.4%, current efficiency 40%.

Claims (19)

1, process for preparing solid potassium ferrate is characterized in that:
A. use diaphragm electrolytic cell, as anode, as negative electrode, place anolyte compartment and cathode compartment respectively with nickel foam or nickel plate or iron plate with iron-bearing materials with electron conduction;
B. being anolyte with the dense KOH solution that contains additive, is catholyte with dense KOH solution, carry out using the direct current electrolysis under the violent stirring at antianode liquid, and in electrolytic process with the suitable amount anode of used electric current liquid in add KOH;
C. the solid state electrolysis product that generates in the anolyte is separated from anolyte,, promptly made the solid potassium ferrate that purity is 90-95wt% through dehydration, dealkalize, drying.
2, process for preparing solid potassium ferrate is characterized in that:
A. use diaphragm electrolytic cell, as anode, as negative electrode, place anolyte compartment and cathode compartment respectively with nickel foam or nickel plate or iron plate with iron-bearing materials with electron conduction;
B. being anolyte with the dense KOH solution that contains additive, is catholyte with dense KOH solution, carry out using the direct current electrolysis under the violent stirring at antianode liquid, and in electrolytic process with the suitable amount anode of used electric current liquid in add KOH;
C. the solid state electrolysis product that generates in the anolyte is separated from anolyte, being dissolved in concentration again is in the NaOH solution of 7-10M, and this solution and saturated KOH solution are replaced suction filtration in the saturated KOH solution that contains the potassium ferrate crystal seed;
D. the potassium ferrate solid that will obtain through suction filtration again through dehydration, dealkalize, drying, promptly makes the solid potassium ferrate that purity is 95-98%.
3,, it is characterized in that used barrier film is a kind of in polyvinyl microporous membrane, polyvinyl ionic membrane, perfluor microporous membrane, the perfluorinated ionic membrane according to claim 1 or 2 described process for preparing solid potassium ferrate.
4,, it is characterized in that said iron-bearing materials is a kind of in common iron net, iron plate, iron filings, the magnetite according to claim 1 or 2 described process for preparing solid potassium ferrate.
5,, it is characterized in that said magnetite is the natural magnet breeze through magnetic separation, pickling, through adding CaO, K according to the described iron-bearing materials of claim 4 2O, Al 2O 3, Co 2O 3, CeO, V 2O 5In more than one after, the magnetite powder that forms through fusion or the whole block magnetite of moulding wherein add components contents and are respectively CaO 0.5-1.2wt% again; K 2O 0.5-2.2wt%; Al 2O 31.5-4.2wt%; Co 2O 30.5-1.5wt%; CeO 0.5-1.5wt%; V 2O 50.5-1.0wt%.
6, according to claim 1 or 2 described process for preparing solid potassium ferrate, when it is characterized in that using iron filings and magnetite powder as anode, with the magnet of surface after insulation is handled these body of powder are fixed on and have on the ferromagnetic iron plate or iron net surface, and allow the one side of body of powder towards negative electrode as the anode current collector body.
7, according to claim 1 or 2 described process for preparing solid potassium ferrate, it is characterized in that the concentration of KOH in the said catholyte is 10-13M, the concentration of KOH is 10-13M in the anolyte, content of additive is 5-25ml/LKOH in the anolyte.
8,, it is characterized in that additive therefor is to contain CuCl simultaneously according to claim 1,2 or 7 described process for preparing solid potassium ferrate 2, KIO 3, Na 2SiO 3, KI KOH or the NaOH aqueous solution, wherein CuCl 2Concentration be 0.005-0.05M, KIO 3Concentration be 0.005-0.05M, Na 2SiO 3Concentration be that the concentration of 0.02-0.8M, KI is that the concentration of 0.001-0.1M, KOH is 2-5M; The concentration of NaOH is 2-5M.
9, according to claim 1 or 2 described process for preparing solid potassium ferrate, it is characterized in that the apparent current density of direct current continuous current that electrolysis is used is 1.0-10.0A/dm 2, the allowed band that bath voltage changes in the electrolytic process is the 2-10 volt.
10, according to claim 1 or 2 described process for preparing solid potassium ferrate, the temperature controlling range that it is characterized in that electrolytic solution is 30-80 ℃.
11, according to claim 1 or 2 described process for preparing solid potassium ferrate, the ratio of selected electric current is when it is characterized in that adding in the anode liquid amount of KOH and electrolysis: 0.01-0.05molKOH per hour: the 1A electric current.
12, according to claim 1 or 2 described process for preparing solid potassium ferrate, it is characterized in that anolyte after isolating solid potassium ferrate, after adding KOH and additive, return in the anolyte compartment again and recycle.
13, according to claim 1 or 2 described process for preparing solid potassium ferrate, it is characterized in that the solid state electrolysis product in the anolyte, continuing under the electrolytic condition that the mean residence time in anolyte is 3-8 hour.
14, according to claim 1 or 2 described process for preparing solid potassium ferrate, it is characterized in that the solid state electrolysis product in the anolyte can be step negative pressure leaching or centrifugation with separating of anolyte, also can be the negative pressure leaching or the centrifugation of discharging continuously.
15, according to claim 1 or 2 described process for preparing solid potassium ferrate, the used dewatering agent that it is characterized in that dewatering is a kind of in hexanaphthene, dimethylbenzene, the Skellysolve A.
16, according to claim 1 or 2 described process for preparing solid potassium ferrate, the used dealkalize agent of dealkalize is a kind of in dehydrated alcohol, the methyl alcohol more than 96%, the acetone more than 96%.
17, according to claim 1 or 2 described process for preparing solid potassium ferrate, the method that it is characterized in that drying treatment is for placing the capacity siccative in vacuum drying oven, elder generation's normal temperature drying under reduced pressure, make in the solids weight percent content of water reduce to about 5%, heat drying or normal pressure heat drying then reduce pressure, the weight percent content of water is reduced to below 1%, and the temperature of heating should be lower than 80 ℃.
18, according to the described process for preparing solid potassium ferrate of claim 2, it is characterized in that finishing the suction filtration time is 20-40 minute.
19,, it is characterized in that temperature should be lower than 30 ℃ in the filter flask according to the described process for preparing solid potassium ferrate of claim 2.
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