Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G23/00—Compounds of titanium
  • C01G23/003—Titanates
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J39/00—Cation exchange; Use of material as cation exchangers; Treatment of material for improving the cation exchange properties
  • B01J39/08—Use of material as cation exchangers; Treatment of material for improving the cation exchange properties
  • B01J39/09—Inorganic material
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G23/00—Compounds of titanium
  • C01G23/003—Titanates
  • C01G23/005—Alkali titanates
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/51—Particles with a specific particle size distribution
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
  • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/12—Surface area

Definitions

• the invention concerns a procedure for manufacturing titanates.
• radioactive waste solutions are produced in ample quantity.
• the aim is, by treatment of these wastes, both to reduce their volume and to solidify them for easier subsequent handling and storing.
• ion exchangers are one of the most important ways to bind radionuclides from waste solutions.
• Organic ion exchangers which are employed in cleaning the primary circuits of nuclear reactors, are however not suited for use in solidifying high-active waste because they cannot tolerate high radiation doses. Instead, organic ion exchangers are used in solidifying power plant waste, the ion exchangers loaded with waste being immobilized, most commonly, in cement or bitumen.
• Inorganic ion exchangers which group also includes titanates, are better appropriate for solidifying especially high-active waste. They tolerate radiation well as a rule. They may be used, for instance
• the ultimate object of nuclear waste treatment is to achieve a low-soluble, both mechanically durable and radiation and heat resistant final waste product.
• Inorganic ion exchangers are converted into final waste product either as they are at high pressure and temperature, or by admixing to them vitrifying or ceramizing substances before they are heated.
• Titanates are inorganic ion exchangers. They have the structure of hydrous oxides.
• sodium titanate is synthesized as follows:
• sodium titanate is synthesized from titanium tetrachloride and sodium hydroxide.
• the object of the invention is to achieve an improvement in procedures for the manufacturing of titanates known at present.
• the more detailed object of the invention is to provide a procedure which is substantially simpler and less expensive than any procedures of prior art.
• the other aims of the invention and the advantages gainable with its aid will become apparent from the disclosure of the invention.
• the procedure of the invention offers a single-step titanate synthesis based on an inexpensive and readily available raw material, titanium dioxide hydrate, which is obtained e.g. as an intermediate in the titanium dioxide pigment industry, and on a simple process technology.
• the product obtained by the procedure of the invention, titanate has high capacities for radionuclides; it tolerates radiation exceedingly well; and it can be ceramized to final waste product.
• the raw material of the titanate synthesis is titanium dioxide hydrate mass.
• the titanium dioxide hydrate mass is an intermediate from the manufacturing of titanium dioxide pigment, from the so-called sulphate process.
• ilmenite mineral mineral formula FeTiO 3
• the "extraction cake" obtained in this reaction is dissolved in water or in a weak acid, whereby a mixture of titanium sulphate and iron sulphates is produced.
• the ferrisulphate is reduced to ferrosulphate and removed by filtering.
• the solution is then concentrated and the concentrated titanium sulphate solution is converted by hydrolysis to titanium dioxide hydrate, which is the initial substance for the titanate synthesis. Its dry matter content is about 40 %. As a result of the process, it is exceedingly acidic.
• the titanium dioxide hydrate mass is suspended in water or in an organic solvent, e.g. ethanol, propanol or butanol, at weight proportions 1/10-1/5.
• the mixture is heated to the boiling point (water 100oC, water/ethanol 78oC, water/propanol 88oC, water/- 1-butanol 93oC) .
• a 20-40 % aqueous solution of an alkali or earth alkali metal hydroxide, such as NaOH, KOH or Ca(OH) 2 , NH 3 or of an organic amine, such as hydrazine, mono, di or trimethylamine, is slowly added at weight proportion 1/3-1/1 referred to the wet weight of the titanium hydrate.
• the bases it is possible by varying the bases, or when several different bases are used in one synthesis by varying their proportions, to influence the sorption properties of the product, in particular its ion selectivity.
• the mixture After adding the base, the mixture is allowed to react at the boiling point of the azeotrope, with powerful agitation, 2-4 hours. The mixture is left to stand over night and filtered and washed with water for 1-2 days. Drying at 105-110oC for 24 hours. The product is cake-like and can be ground and sieved to separate the desired grain sizes.
• One sodium titanate product has the chemical composition:
• This sodium titanate had specific surface area 12 m 2 /g.
• the product in completed form is cake-like. It can be ground and the different grain sizes can be separated by sieving. The greater part of the grains obtained are suitable for column use, and the grains are mechanically durable enough. The finest granular material may be used for batch equilibrations.
• the strontium sorption half-time is dependent on the grain size of the sodium titanate, the half-time with grain size 0.071-0.140 mm being
• the distribution coefficient is also higher than in the latter case by a factor over 4, i.e., 5.6 x 10 4 .
• the sorption capacities of sodium titanate are high.
• the capacities determined by column experiments are: for strontium 1.4 mmol/g, cesium 1.5 mmol/g and cobolt 1.8 mmol/g.
• the distribution coefficients increase powerfully with increasing pH, being at pH higher than 6: several ten thousand for strontium, several thousand for cobolt, but for cesium only from a few tens to hundreds.
• the sorption mechanism is not fully understood.
• the exchangeable ion in sodium titanate is sodium. Since Sr, Cs and Co exchange the stoichiometric quantity of sodium, this suggests chemical ion exchange. Sorption takes place in two steps. The greater part of the sorption is very rapid. At the second step the sorption is lower by one order of magnitude. The first step is believed to be exchange onto the surface of the grains and to the fine dust that is present. The second step would seem to be exchange into the grains.
• Sodium titanate tolerates radiation very well.
• a 10 Gy gamma dose has no effect on the sorption capacity, on structure, nor on the specific surface area.
• the finest granular material may be used in batch operation. This material is added to the waste solution and mixed during a couple of hours at the most. The material is then either separated e.g. by filtering, or red clay or other brick clay is admixed to it for baking. In the first instance, the filtered titanate is usually dried at a few hundred degrees and ceramized after grinding.
• Titanates may be used in columns either completely separated or to the purpose of binding the waste nuclides remaining in the residual solution from batch running. After the use, the material is removed from the column and it is usually dried, ground and ceramized.
• the evaporator waste concentrates of nuclear power stations have greatly variable origins. They present a high salt concentration as a rule. Titanates may best be applied to solidify them by equilibrating the waste and titanate in a batch, by thereafter adding brick clay and by preparing a brick. 4-M sodium concentration, which corresponds to the true situation in evaporator wastes, lowers the distribution coefficient of strontium in sodium titanate by one order of magnitude. A boric acid concentration of 1-M, also consistent with actual situations, lowers the distribution coefficient of strontium by one order of magnitude. The capacity is still high enough in spite of salt concentrations as mentioned above.
• the organic ion exchangers removed from the primary circuits of reactors are, on the side of the evaporator concentrates mentioned, the most important source of medium activity waste. At present they are usually embedded in concrete or bitumen.
• an alternative possibility is to elute the waste nuclides from the resins and to bind them e.g. to titanate in columns.
• complex-forming agents such as oxalates, citrates and EDTA.
• oxalates, citrates and EDTA One possible eluant , sodium citrate, causes no substantial weakening of the sorption of strontium in sodium titanate.
• EDTA significally lowers the sorption at pH over 6.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Environmental & Geological Engineering (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geology (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Inorganic Compounds Of Heavy Metals (AREA)
• Manufacture And Refinement Of Metals (AREA)

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• 1982
  • 1982-04-30 FI FI821535A patent/FI821535L/fi not_active Application Discontinuation
• 1983
  • 1983-04-26 EP EP83901347A patent/EP0107689A1/en not_active Withdrawn
  • 1983-04-26 WO PCT/FI1983/000036 patent/WO1983003819A1/en unknown

Non-Patent Citations (1)

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