Classifications

• • 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
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
  • B01J20/0203—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of metals not provided for in B01J20/04
  • B01J20/0211—Compounds of Ti, Zr, Hf
• • 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
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
  • B01J20/28014—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their form
  • B01J20/2803—Sorbents comprising a binder, e.g. for forming aggregated, agglomerated or granulated products
• • 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
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/20—Two-dimensional structures
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
  • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
• • 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

• This invention concerns a novel partially crystalline sodium nonatitanate composite having a layered structure.
• the novel sodium titanate exhibits ion exchange properties, and it is particularly designed to be an excellent ion-exchanger for strontium.
• Much of the stored nuclear waste is in the form of sludge created when alkali was added to the waste to prevent tank corrosion.
• Some of the radioactive material has been incorporated into salt cakes which is the evaporative product of the alkaline aqueous material. It is desired to remove the radioactive elements from the waste in order to allow for subsequent safe disposal of the non-radioactive materials.
• the removal of two of the metallic radionuclides, cesium and strontium, is particularly important because their half-lives are long enough to represent a hazard for an extended period of time.
• Sodium nonatitanate is known as a strontium ion exchanger. J. Lento; J. Radioanal. Nucl. Chem. Letters, 118: 1-13 (1987) describes the ion exchange behavior of Na 4 Ti 9 O 20 • xH 2 0 toward strontium.
• the sodium titanate was prepared hydrothermally at 300° C followed by boiling with NaOH.
• PCT Application WO 94/19277 discloses silico-titanates and methods for making and using them.
• the silico-titanates disclosed are useful for removing cesium from radioactive wastes.
• U.S. Patent 4, 156,646 discloses removal of plutonium and americium from aqueous alkaline waste solutions using sodium titanate ion exchangers.
• the sodium titanate used is a monosodium titanate.
• U.S. Patent No. 5,352,644 describes a titania bound zeolite made by combining the zeolite, a low acidity titania binder material, and an aqueous slurry of titanium oxide hydrate.
• this invention is a partially crystalline layered sodium titanate having a d-spacing of from about 8 to about 9.5 angstroms.
• this invention is a partially crystalline layered sodium titanate having a d-spacing of from 9.0 to 9.9 angstroms, a Langmuir surface area of from about 60 to about 110 m 2 /g, and 001 reflection peak width greater than 1 degrees and less than about 4.5 degrees.
• this invention is a partially crystalline layered sodium titanate composite having the x-ray diffraction pattern of Figure 1 prepared by hydrothermally treating a sodium titanate gel at a temperature of from about 120°C to about 200°C in the presence of aqueous NaOH for a period of time ranging from about 1 to about 20 hours.
• this invention is a partially crystalline layered sodium titanate having a d-spacing of from 9.0 to 9.9 angstroms, a 001 reflection peak width greater than 2 degrees and less than about 4.5 degrees prepared by the method comprising hydrothermally treating a sodium titanate gel prepared by a reflux method and then hydrothermally treating the reflux product at a temperature of from about 150°C to about 170 °C in the presence of added aqueous NaOH for a period of time ranging from about 1 hour to about 20 hours.
• Figure 1 is an X-ray diffraction pattern of a layered partially crystalline sodium titanate composite of this inven ⁇ on having a d-spacmg of 9.4 angstroms;
• Figure 2 are X-ray diffraction patterns of partially crystalline layered sodium titanate samples 1-1 to 1-6 as prepared in Example 1 ;
• Figure 3 are X-ray diffraction patterns of partially crystalline layered samples 1-7 to 1-13 as prepared in Example 1 ;
• Figure 4 is an X-ray diffraction pattern of partially crystalline layered sodium titanate sample 2-1 prepared in Example 2.
• Figure 5 is a plot of the log (K versus pH for the uptake of strontium by sodium titanate
• Figure 6 is the X-ray diffraction pattern of dehydrated layered partially crystalline sodium titanate of this invention having a d-spacing of 9.00 angstroms as prepared in Example 9;
• Figure 7 is the X-ray diffraction pattern of hydrated layered partially crystalline sodium titanate that has a d-spacing of 10.2 angstroms as prepared in Example 9;
• Figure 8 is a plot of the strontium uptake of a partially crystalline layered sodium titanate prepared in Example 5 as a function of the full-width half maximum (FW ⁇ M) peak height of the 001 reflection peak wherein FWHM and sodium titanate crystalhnity are inversely related.
• FW ⁇ M full-width half maximum
• Figure 9 is a plot of the internal temperature in a reactor vs. time du ⁇ ng sodium titanate hydrother al treatment
• Figures 10A, 10B, IOC, and IOD are scanning electron micrographs (SEM) of each hydrothermally treated pilot plant batch of partially crystalline layered sodium titanate prepared in Example 5 magnified 3000 times;
• Figure 11 is a plot of the concentration of strontium in the effluent of a partially crystalline layered sodium titanate packed column over time before and after regeneration of the sodium titanate ion exchange material.
• Figure 12 is a plot of the kinetics of strontium uptake by bound and unbound partially crystalline layered sodium titanate of this invention.
• the present invention relates to a partially crystalline layered sodium titanate having a d-spacing of from about 8 to about 9.9 angstroms, and a 001 reflection peak half width of from
• the new partially crystalline sodium titanate has strong ion exchange properties towards strontium as a result of physical properties that distinguish the composition from all other sodium titanates.
• the partially crystalline layered sodium titanate of this invention has the formula Na 3 4 . 4 4 Ti 8 4 - 9 2 , g 5 20 6 • *H 2 O. It is preferred that the partially crystalline layered sodium titanate has the formula • TH 2 O.
• the non-crystalline layered sodium titanate of this invention also comprises amorphous sodium titanate. As will be discussed below, the combination of the layered partially crystalline sodium titanate and amorphous sodium titanate is the result of hydrothermally treating sodium titanate gel at specified conditions. The resulting partially crystalline layered sodium titanate has a unique X-ray diffraction pattern as well as other unique physical and performance characteristics.
• the partially crystalline layered sodium titanate of this invention has been formulated to maximize its strontium ion exchange capacity and selectivity.
• the strontium ion-exchange property has been deliberately manufactured into the sodium titanate of this invention by controlling the sodium titanate hydrothermal treatment step to produce a sodium titanate product that it is partially crystalline.
• the hydrothermal treatment variables that affect the crystallinity of the sodium titanate product and, thereby, its strontium ion-exchange capacity and selectivity are, hydrothermal treatment temperature, the time of treatment, and the concentration of sodium hydroxide used in the hydrothermal treating solution.
• An additional advantage of the hydrothermal treatment is that it renders the sodium titanate essentially insoluble in strongly alkaline solutions.
• Various methods are used to prepare a sodium titanate gel for hydrothermal treatment.
• Strontium ion-exchange affinity is measured by the strontium distribution coefficient, K j .
• the distribution coefficient, K d is calculated using the following equation:
• C, and C f are the initial and final solution concentrations of strontium or any other solution ion being tested
• V is the volume of the starting test solution
• W is the weight of the sample tested.
• K d is typically reported in units of mL/g.
• the strontium K d is determined by contacting a known sample of sodium titanate with a solution of known strontium concentration for a controlled period of time, preferably 24 hours.
• Strontium Kj is solution specific and for most K d 's reported herein, a solution consisting of 5M NaNO 3 /0. IM NaOH/55ppm Sr was used. If a reported K d is derived from different strontium containing solution, then the solution composition is reported.
• the strontium K d of sodium titanate is a function of sodium titanate crystallinity. If the sodium titanate product is too crystalline, mass transfer into the sodium titanate will be slowed thereby lowering the strontium Kj. Likewise, if the sodium titanate is not crystalline enough, the sodium titanate will not have the requisite d-spacing to be a good strontium exchanger and the strontium Kj will be low. Thus the sodium titanate of this invention is characterized as "partially crystalline" — the crystallinity of the sodium titanate of this invention is tailored during the hydrothermal treatment step to control d-spacing and other physical properties, thereby maximizing the strontium K d of the partially crystalline sodium titanate composition.
• At least three physical properties are characteristic of a partially crystalline layered sodium titanate composition of this invention with the required crystallinity to be a good strontium ion exchanger.
• the properties are, strontium K d , X-ray diffraction d-spacing, and the
• 2dsin0 n ⁇
• d is the d-spacing in angstroms
• n is an integer
• ⁇ is the X-ray wavelength in angstroms
• ⁇ is the X-ray angle of reflection in degrees.
• the Bragg's Law Equation is a useful tool for interpreting X-ray diffraction patterns since the X-ray diffraction pattern is a trace of 20.
• the spacing between the sodium titanate layers is ascertained from the x-ray diffraction pattern using Bragg's Law and is known as d-spacing.
• Sodium titanate is composed of layers of titanium and oxygen atoms separated by voids containing sodium ions and water.
• the d- spacing is the distance from one titanium or oxygen atom to the identical atom one crystal layer away.
• D-spacing is the thickness of one titanate layer and one void space.
• the sodium titanate of this invention must have a d-spacing of from 8 to 9.9 angstroms, and preferably a d-spacing of from about 9.0 to about 9.9 angstroms.
• a sodium titanate having the requisite d-spacing admits hydrated strontium, excludes hydrated sodium, and exhibits strontium K d s in excess of 20,000 mL/g.
• High strontium K ⁇ 's are obtained when the FWHM is greater than 1 degrees and less than about 4.5 degrees: 1.0 degrees ⁇ FWHM ⁇ 4.5 degrees, and most preferably when the FWHM is greater than 2 degrees and less than about 4.5 degrees: 2.0 degrees ⁇ FWHM ⁇ 4.5 degrees.
• the layered structure of partially crystalline sodium titanate of this invention is the source of its ability to selecuvely exchange strontium.
• the partially crystalline sodium titanate composition contains spaces between the layers that are large enough to accept hydrated strontium ions. The layer spacing is small enough, however, to exclude hydrated sodium and this prevents hydrated sodium from competing for ion-exchange sites with hydrated strontium.
• Sodium titanate surface area is related to the rate at which an ion exchanges. The larger the surface area, the faster the strontium exchange rate. Typically, the greater the crystal nity of sodium nonatitanate the lower its surface area is. Thus, there is also a fine balance between crystallinity and exchange rate.
• a partially crystalline sodium titanate of this invention will have a surface area of from 25-200 m 2 /g It is preferred, however, that the partially crystalline sodium titanate of this invention has a surface area of from 60 to 1 10 m 2 /g.
• Partially crystalline layered sodium titanates of this invention can be prepared by at least two techniques; by the sol-gel technique, and by the reflux technique. Both techniques produce a sodium titanate gel that must undergo hydrothermal treatment which crystallizes at least a portion of the sodium titanate gel to give a partially crystalline layered sodium titanate of this invention. It is the parameters of the hydrothermal treatment parameters, including the NaOH concentration, that are important for producing a partially crystalline sodium titanate composition that has the desired Kj, d-spacing, and FWHM properties.
• the sol-gel method for preparing a sodium titanate gel comp ⁇ ses combining titanium isopropoxide and methanol at a weight ratio of from 1: 1 to about 1 : 100 to form a first reaction mixture.
• a second reaction mixture is prepared by combining NaOH and methanol in a weight ratio that allows the sodium hydroxide to dissolve completely in the methanol.
• the first reaction mixture is added to the second mixture to form an admixture and a third reaction mixture comprising water and methanol slowly added to the admixture to initiate gel formation.
• the final mixture is allowed to gel for a period of time ranging from about 15 minutes to about 2 hours or more.
• the reactor is sealed and agitated at a high rate for a period of time of 30 minutes or longer to keep the sodium titanate gel fluid.
• the solvent and byproducts are then evaporated from the sodium titanate gel in a vacuum oven operated at from 40°C to about 80 °C for a period of time ranging from about 2 hours to about 24 hours or more until most of the methanol solvent and reaction byproduct, isopropanol, is volatilized from the sodium titanate gel.
• An alternative and preferred method for producing sodium titanate gel is the reflux method.
• the reflux method does not use methanol and only produces the corresponding isopropanol byproduct thereby reducing the amount of volatile fumes and wastes produced by the sodium titanate gel formation process as well as making solvent recovery easier and more energy efficient.
• the reflux process comprises first preparing a solution of sodium hydroxide by dissolving sodium hydroxide pellets in deionized water to give a first solution consisting of from about 10 molar to about 19.2 molar NaOH. Neat - 99% - titanium isopropoxide (TiP) is then added slowly to the first solution until the mole ratio of Ti to Na in the mixture ranges from 1 : 1 to 1 : 10, and preferably from 1 :5 to 1 :9. The sodium hydroxide/titanium isopropoxide mixture is then refluxed for a period of time ranging from about 60 minutes to about 4 hours or more at a temperature of from 100-150°C to form an amorphous sodium titanate gel.
• the sodium titanate gel produced by either method must be hydrothermally treated in order to produce the partially crystalline layered sodium titanate of this invention.
• the hydrothermal treatment is accomplished in a reactor at a pressure ranging from about 45 to about 1000 psig and at a temperature ranging from about 100 to about 250° C.
• the sodium titanate gel is hydrothermally treated for a period of time ranging from about 1 hour to about 1 day or more.
• the hydrothermal treatment occurs, the autogenous pressure in the reactor vessel increases with increasing temperature. Therefore, the preferred average reactor pressure during hydrothermal treatment ranges from about 50 psig to about 350 psig depending on reaction temperature.
• the hydrothermal treatment may occur under alkaline conditions created by adding water or a sodium hydroxide solution to the sodium titanate gel before or after it is added to the hydrothermal treatment reactor or autoclave.
• the hydrothermal treatment step may be repeated at least once in order to increase the crystallinity of the partially crystalline sodium titanate.
• the hydrothermal treatment step is preferably conducted for 1 to about 20 hours at 160-200°C. By reducing the temperature of the hydrothermal treatment from 200 °C to
• the autogenous pressure is reduced from 247 to 90 psia, thereby making the process safer and requiring less expensive equipment.
• the time reduction from 20 hours to 5 greatly increases the overall productivity of the process.
• a partially crystalline sodium titanate will not be crystalline enough to have the physical properties of a partially crystalline layered sodium titanate of this invention.
• the partially crystalline sodium titanate can be hydrothermally treated a second and possibly subsequent times at the conditions recited above in order to increase the crystallinity of the partially crystalline sodium titanate to the desired level.
• Table 1 shows that the strontium K ⁇ of a partially crystalline layered sodium titanate can be improved in some cases by a second hydrothermal treatment.
• the partially crystalline layered sodium titanate of this invention has the formula Na, 4 . 44 Ti 8 4 . 9 2 O,g 5 . 206 .
• the partially crystalline sodium titanate is removed from the reactor and washed with deionized water and filtered.
• the washed product is dried at a temperature from about 50°C to about 100 C C for a period of time ranging from about 3 hours to about 2 days or more.
• the amount of sodium hydroxide added to the sodium titanate gel can be a c ⁇ ticai hydrothermal treatment parameters and must be closely controlled in order to produce a sodium titanate having an op ⁇ mum crystallinity for strontium ion exchange.
• the amount of sodium hydroxide added to the sodium titanate gel during hydrothermal treatment should range from about O.OM to about 6M, and preferably from 0.50M to about 1.5M.
• the sodium titanate gel inherently is naturally contaminated with NaOH. So sodium hydroxide will become dissolved in any water added to the sodium titanate gel du ⁇ ng gel hydrothermal treatment. It is preferred, however, that an aqueous solution of NaOH in the mola ⁇ ty ranges given above be added to the sodium titanate gel p ⁇ or to hydrolysis.
• the optimum hydrothermal treatment temperature is from about 100°C to about 250°C and preferably from 160-200°C.
• the strontium Kj of the resulting partially crystalline sodium titanate is at least 20,000 mL/g based on 20mL of solution consisting of 55 ppm Sr/5M NaNO 3 /0. IM NaOH added to 200 mg of solid sample.
• the partially crystalline sodium titanate of this invention is very useful when used as an ion exchanger.
• it In order to use the powdered partially crystalline sodium titanate as an ion exchanger, it must be bound into larger particles to reduce the pressure drop in the ion exchange column and to ease handling. Any binder known in the art for binding catalysts and lon- exchangers may be used.
• the bound sodium utanate of this invention is very useful in removing strontium and other radioactive waste from highly caustic aqueous solutions. So, it is preferred that the binder be selected from materials that withstand radiation and alkaline conditions, and the material should not inhibit or block strontium or other ions from entering the partially crystalline layered sodium titanate.
• a composite material made up from 40 to 95 wt% of partially crystalline sodium titanate with 5-60 wt% of a binder is preferred.
• Both organic and inorganic binders can be mixed with partially crystalline sodium titanate to make a bound ion exchange composition for strontium.
• inorganic binders offer the advantage of increased radiation resistance.
• organic binders may be easier to extrude into pellets than inorganics.
• inorganic binders include silica or silica gel, silicon carbide, clays, and silicates, including synthetically prepared and naturally occurring ones, which may or may not be acid treated, for example, attapulgus clay, china clay, diatomaceous earth, fuller's earth, kaolin, kieselguhr, etc.; ceramics, porcelain, crushed firebrick, bauxite; refractory inorganic oxides such as alumina, titanium dioxide, zirconium dioxide, chromium oxide, beryllium oxide, vanadium oxide, cerium oxide, hafnium oxide, zinc oxide, magnesia, boria, tho ⁇ a, silica- alumina, silica-magnesia, chromia-alumina, alumina-boria, silica-zirconia, etc.
• crystalline zeolitic aluminosilicates such as naturally occurring or synthetically prepared mordenite and/or faujasite, for example, either in the hydrogen form or in a form which has been exchanged with metal cations; spinels such as MgAl 2 O 4 , AnAl 2 O 4 , CaAl 2 O 4 , and other like compounds; and combinations of materials from one or more of these groups.
• spinels such as MgAl 2 O 4 , AnAl 2 O 4 , CaAl 2 O 4 , and other like compounds; and combinations of materials from one or more of these groups.
• inorganic binders include various metal salts in powder, sol, or gel form, as well as graphite and hydraulic cement may be used to bind any type of sodium titanate.
• Ciment Fondo XR calcium aluminate, and Portland type 3 cement are good sodium titanate binders with excellent strength and resistance to high alkalinity.
• the bound sodium titanate can be in the form of pellets, can be fashioned with dies, or extruded.
• Organic binders may also be used to bind partially crystalline sodium titanate. Examples of organic binders include polymers, starches, cellulose, cellulose acetate and other organic catalyst and ion-exchanger binders known in the art.
• Pore formers, surface area enhancers and other materials may be added to the partially crystalline sodium titanate before, during, or after binding to improve the porosity and surface area of the bound crystalline sodium titanate.
• a preferred pore former is one which can be removed from the ion-exchanger chemically, or thermally before the bound material is used as an ion-exchanger.
• a preferred binder is a hydrolyzable titanium compound.
• the hydrolyzable titanium compound is useful for binding any form of crystalline titanates including crystalline sodium titanates, crystalline hydrogen titanates, and the preferred partially crystalline sodium titanate.
• a hydrolyzable titanium compound of this invention will have the formula Ti XX,X bossX ⁇ wherein
• X is any constituent, and X tractX ⁇ ,and X m are each chosen from the group consisting of Cl, Br.
• hydrolyzable titanium compounds include titanium alkoxides and especially titanium isopropoxide.
• the hydrolyzable titanium compound is preferably used to bind a form of crystalline sodium titanate that is a good strontium ion exchanger because the resulting titania binder has little detrimental impact on the strontium K d of the bound product.
• a preferred crystalline sodium titanate is a partially crystalline sodium titanate having the formula: Na 3 4. 4 4 Ti 8 4.92 ⁇ 18 5-20.6. a d-spacing of from 8.0 to 9.9, and a (001) reflection peak half-width greater than 1 ° and less than about 4.5°.
• the hydrolyzable titanium compound preferably titanium isopropoxide, and a crystalline sodium titanate are combined and water from the air and from the crystalline sodium titanate slowly hydrolyze the hydrolyzable titanium compound to form a titania bound crystalline sodium titanate.
• the titania bound crystalline sodium titanate may be bound in the presence of an alcohol such as methanol in which case the solid should be dried before use or before further processing.
• the titania bound crystalline sodium titanate may be dried at ambient conditions or it may be dried in an oven. In a preferred method, the titania bound crystalline sodium titanate is dried in an oven at a temperature of from 75 °C to about 100°C for a period of time ranging from about 1 hour to about 12 hours or more.
• the dried titania bound crystalline sodium titanate can be used as is, it can be ground and sieved into smaller particles for use as an ion exchanger, or it can be processed further to improve its mechanical properties. It is preferred that the dried titania bound crystalline sodium titanate is further processed first by compaction, and then by calcination.
• the dried titania bound crystalline sodium titanate can be compacted as produced, or it can be ground into small particles, or into a powder and then compacted. It is preferred that the dried titania bound crystalline sodium titanate is ground into smaller particles that can be easily compacted.
• the titania bound crystalline sodium titanate may be compacted in any powder compaction equipment known such as molding presses, tableting presses, and extruders.
• Molding presses comprise a mechanically or hydraulically operated press and a two part mold attached to the platens of the press, consisting of top (male) and bottom (female) portions. The action of pressure and heat cause a particulate charge to flow and take the shape of the cavity of the mold.
• a single-punch press is one that will take one station of tools consisting of an upper punch, a lower punch, and a die.
• a rotary press employs a rotating round die table with multiple stations of punches and dies.
• Older rotary machines are single-sided; that is, there is one fill station and one compression station to produce one tablet per station at every revolution of the rotary head.
• Modern high-speed rotary presses are double-sided; that is, there are two feed and compression stations to produce two tablets per station at every revolution of the rotary head.
• the titania bound crystalline sodium titanate may be dry granulated.
• dry granulation the blended dry ingredients are first densified in a heavy-duty rotary tableting press which produces pellets. The pellets are subsequently crushed into particles of the size required for ion exchange. Densification can also be accomplished using a rotary compactor-granulator system.
• a third technique, direct compaction uses sophisticated devices to feed the blended dry ingredients directly to a high-speed rotary press. Roll presses can also be used to tablet the Utania bound crystalline sodium titanate by directing a powder feed into a gap between two rolls rotating at equal speeds.
• the size and shape of the compacted pellets are determined by the geometry of the roll surfaces. Pockets or indentations in the roll surfaces form b ⁇ quettes from a few grams up to 5 lb. or more in weight. Smooth or corrugated rolls produce a solid sheet which can be granulated in the desired particle size on conventional grinding equipment.
• Lubricants added to the powder feed can aid in the transmission of compaction forces and reduce sticking to the die surfaces.
• Lub ⁇ cants that are removed from the bound mate ⁇ al at calcining temperatures may be incorporated into the titania bound crystalline sodium titanate p ⁇ or to compaction.
• Such lub ⁇ cants may be selected from the group comp ⁇ sing bone acid, graphite, oils, soaps, starch, stea ⁇ c acid, and waxes.
• a preferred lub ⁇ cant is stea ⁇ c acid and it is preferably present in the powder compactor feed in an amount ranging from about 0.1 to 4.0 weight percent.
• the compaction step should produce a compact particle or pellet having a piece density ranging from about 1.5 to about 2.5 g/ml. It is most preferred that the compressed titania bound crystalline sodium titanate particle has a piece density ranging from 1.8 to 2.2 g/ml
• the compacted titania bound crystalline sodium titanate particles are calcined at a temperature ranging from about 150°C to about 500°C for a pe ⁇ od of ume ranging from 30 minutes to 10 hours or more. It is preferred that the particles are calcined in air at a temperature of from about 200°C to about 400°C for a pe ⁇ od of time ranging from about 30 minutes to about 5 hours. It is most preferred that the particles are calcined in moist air at the conditions identified above.
• Bound and unbound sodium titanate ion exchangers are useful in removing strontium and other radioactive and non-radioactive metals form aqueous solutions by packing bound or unbound sodium titanate into a column and removing target metals from the aqueous streams which are fed in to the column. Using this configuration, crystalline sodium titanate can remove metals form large volumes of aqueous solutions. Sodium titanate ion-exchangers can also be regenerated with an acid, and reused without loss of performance.
• bound crystalline sodium titanate is able to remove strontium from aqueous streams having a pH of at least 9.95 up to 13 or more, and a Na ion molarity of from about 1.0 to about 5.0 or more without significant loss of exchanger capacity or physical integrity.
• the ion-exchange columns When used in processing nuclear waste, the ion-exchange columns should be made out of glass, and may be lined with a polymer for caustic protection. Once the exchanger is spent, the sodium titanate, along with the glass column can be vitrified to act as a impervious barrier for the radioactive strontium.
• the unbound and bound sodium titanate of this invention is useful as an ion exchanger for metals besides strontium.
• the sodium titanate is useful, either alone or bound, in removing actinides, and especially uranium, from aqueous solutions. Other actinides which can be similarly removed include thorium, plutonium and americium.
• Sodium titanate may be used as an ion-exchanger as produced or it may be converted into H-titanate and used as an ion-exchanger for metals such as ytterbium, zirconium, molybdenum, silver, thallium, lead, chromium, vanadium, iron, cesium, tin, arsenic, and other metal ions with a high affinity towards hydrogen titanate.
• metals such as ytterbium, zirconium, molybdenum, silver, thallium, lead, chromium, vanadium, iron, cesium, tin, arsenic, and other metal ions with a high affinity towards hydrogen titanate.
• the sodium titanate of this invention is also useful either alone or with a binder, to exchange a wide variety of metals at alkaline conditions.
• the metals are ranked according to uptake in Table 2 below.
• lithium, magnesium, nickel, cobalt, and barium are exchanged by a partially crystalline sodium titanate in amounts equal to or greater than strontium.
• partially crystalline sodium titanate has a high affinity for zinc, copper, cadmium, mercury, thallium, and lead.
• silver has a very high uptake by sodium titanate. As seen in Table 2, these results indicate that sodium titanate can be used to remove metals from industrial effluent and other aqueous metal containing waste, as well as recover target materials.
• the ion exchange results reported in Table 2 are based on batch tests using 200 mg sodium titanate, (sample 5-1 from Example 5, infra) an aqueous 20 mL solution containing 20 ppm of the metal ions being screened, at alkaline conditions (pH 10- 1 1). Sodium was present in all samples, and the results reflect high selectivities for the indicated metals over sodium. Sodium titanate is useful only as a cation exchanger, and therefore it did a poor job exchanging some metals, including As, Sb, Mo, and Pb at high pH.
• This Example describes a reflux method for manufacturing sodium titanate gel of this invention followed by hydrothermal treatment to produce a partially crystalline sodium titanate.
• 5.85 g of NaOH pellets were dissolved in 14 mL of distilled deionized water (DDI). 32 mL of titanium isopropoxide (TiP) was then added slowly to the NaOH solution. This mixture was then refluxed for 3 hrs at which time it was then transferred into a Teflon lined bomb using distilled deionized water (except for Sample 1-2 which used 20 mL of 0.82 M NaOH solution). The bomb was sealed and placed in a 190°C oven and allowed to react for 20 hrs. The material was collected by filtration and washed one time with DDI and three times with methanol. The initial Ti concentration in the bomb was 1.58 M and the initial concentration of NaOH in the bomb was 2.46 M. The Ti:Na ratio was 1 : 1.56.
• Table 3 lists the properties of partially crystalline sodium titanates prepared by the method of this Example.
• the solution used to derive the strontium Kj data included 5M NaNO,, 0. 1M NaOH and 90-95 ppm Sr 2* .
• the solution to sample weight ratio was 200: 1 unless otherwise reported.
• the solution to sample v/w ratio was 250: 1.
• the solution to sample v/w ratio was 400: 1.
• Samples 1-1 to 1-13 are shown in Figures 2 and 3.
• Samples 1 -6, 1-7, and 1- 10 each have d-spacing below 9.9 and greater that 8.0 and 001 reflection FWHM's of between 1 ° and 4.5°.
• This Example describes a method for preparing a sodium titanate designated as sample 2-1 by subjecting sample 1-2 of Example 1 to a second hydrothermal treatment. 3.50 g of sample 1-2 was placed into a Teflon lined bomb. 38 mL of 4.2 M NaOH solution was added to the solid. This mixture was then treated hydrothermally for 2 days at 170°C. The sample was collected by filtration and washed one time with DDI, four times with methanol, and two times with ethanol. The X-ray diffraction pattern of sample 2-1 is found in Figure 4.
• the K d before the second hydrothermal treatment was 3,060 mL/g and after the additional hydrothermal treatment (sample 2- 1), 1270 mL/g.
• This example details the preparation of a partially crystalline layered sodium titanate of this invention by the sol-gel method.
• Solution B was made in a plastic beaker by dissolving 40.793 g of 98.4% NaOH pellets in 400 mL of methanol.
• the NaOH is not readily soluble in methanol. Therefore, the mixture was stirred for over 30 minutes with a magnetic stirrer.
• Solution A was made by mixing 294.2 g of titanium isopropoxide (TiP) and 250 mL of methanol in the reaction vessel. The heat of mixing is exothermic (the temperature reached 72 °
• the reaction vessel was a 2-liter glass beaker wrapped with insulation tape.
• solution B was slowly added to solution A in the reaction vessel.
• the contents were stirred with a magnetic stirrer, and heated to 53 °C on a hot plate.
• Solution C was made in a 100 mL beaker by mixing 20 mL water and 50 L methanol. Using a buret, solution C was added drop-wise to the heated mixture of A and B (53 °C). The resulting sodium titanate gel was mixed for another 15 minutes, then transferred to a ceramic evaporating dish. The solvents were allowed to evaporate overnight in a hood. Next, about half the gel was loaded into a liter round bottom flask, which was then connected to a rotary evaporator. The gel was dried under vacuum for 1.5 hours at 60-75° C. The rotary evaporation procedure was repeated for the second batch. This procedure yielded 135 g of dried gel.
• This example details the preparation of a partially crystalline sodium titanate of this invention using the reflux method followed by hydrothermal treatment.
• a 30% NaOH solution was prepared by dissolving 419.88 g of 98.4% NaOH pellets in 956 g of deionized water. This solution was transferred into a 3000 mL, 3-necked round bottom reaction flask. 295.3 g of titanium isopropoxide (TiP) was added drop-wise from a 500 mL addition funnel into the NaOH solution in the reaction flask. During the addition, the mixture was stirred at 500 rpm. A large amount of white solids precipitated out of solution.
• TiP titanium isopropoxide
• the reaction vessel was placed on a heating mantle, and equipped with a condenser, thermocouple and temperature controller, and mixer. The mixture was stirred at 250 rpm and refluxed at 1 10° C for 5.25 hours. The sodium titanate gel product was allowed to cool and settle out overnight. The water was then decanted, and the solids dried at 60°C for 2 days. The yield was 152 g of sodium titanate gel.
• 10 kg of sodium titanate gel were made using the sol gel method according to this example.
• a 50 gallon reactor was charged with 30 kg titanium isopropoxide and 20.6 kg methanol.
• a solution of 4.2 kg NaOH and 32.8 kg methanol was slowly added from one of several 20 gallon mixing tanks.
• a 2.1 kg water/4.1 kg methanol solution was then slowly added to initiate gel formation.
• Methanol evaporation from the reactor was eliminated by applying pressure, and high agitation rate, (681 ft/min), to keep the gel fluid.
• the d ⁇ ed gel was divided into four batches and treated hydrothermally in a 5 gallon stainless steel-lined autoclave.
• the autoclave liner was capped with a sheet of Teflon.
• Table 4 summa ⁇ zes the conditions of each hydrothermal treatment.
• 4.5 kg of dry gel was hydrothermally treated in 9 kg of water for 20 hours at 160-200° C.
• batches 5-3 and 5-4 2.6 kg of dry gel was treated in 5.2 kg of water for 5 hours at 160- 200°C. All non-stirred batches formed a solid chunk by the end of the autoclave step This solid was easily dispersable in water.
• Batch 5-4 was agitated throughout the treatment The mate ⁇ al from batch 5-4 was a finely suspended slurry, and therefore was very easy to remove from the autoclave.
• the top layer of water on each batch in the autoclave was suctioned off and the remaining solid slurry was transferred to a filter bag within a centrifuge. 7 kg of deionized water was used to wash the solids clinging to the sides of the autoclave. The solids were centrifuged for 10 minutes to remove the water. An additional 4 kg of water was added to the solids and then centrifuged to wash the product. The product was dried overnight in a 65 °C oven with a flowing nitrogen purge. The combined yield of all four batches was 9.2 kg of partially crystalline sodium titanate.
• X-ray powder diffraction (XRD) patterns of the synthesized materials from Examples 1 and 2 were prepared and the results are shown in Figures 1-3.
• the XRD patterns indicate, for the reflux samples, that as the mole ratio of Na/Ti increases, the crystallinity of the titanate material also increases until a ratio of 5 is reached. At this ratio, what appears to be a less crystalline compound, forms.
• sample 2-1 shows that this twice hydrothermally treated sample is more crystalline than its precursor 1-2.
• Samples 2- 1 , 1 -8 and 1-9 exhibited K d values that were considerably lower than those of the less crystalline samples.
• sample 1-8 had a strontium K d of 7000 mL/g in 0.1M NaNO 3 . Under the same conditions, sample 1-1 had strontium K d value in excess of 100,000 ml/g.
• sample 2- 1 A more crystalline variety which appears to resemble sample 2- 1 are samples 1-1 , 1-2, 1-3, and 1-5 and a more gel-like group as exemplified by 1 -6, 1 -7, and 1 -10. and a sample of intermediate crystallinity between the two, sample 1 -4. It is sample types 1 - 10 and
• Sample 1-13 (gel-based) and 1-2 (reflux-based) have similar Na:Ti mole ratios and were reacted for approximately the same time period and temperature, but turn out to be different structure nonatitanates.
• the X-ray diffraction pattern for the gel sample was similar to the high
• EXAMPLE 7 This Example describes the strontium dist ⁇ buuon coefficient (K d ) results for sodium titanates prepared in Examples 1 and 2.
• the dist ⁇ buuon coefficient as defined in this example is the ra ⁇ o of the concentration Sr 2 * in the exchanger to the concentration of Sr + in solution at equi b ⁇ um. Because the analyses were earned out an a weight basis, the units are g/g instead of the usual mL/g.
• the distribuuon coefficients K d ) were determined for Sr 2 " 1" as a function of pH for three of the samples, 1-1 , 1-10, and 2-1. The resulting data are shown in Figure 5. As the pH of the solution decreases, the selectivity for Sr decreases.
• the K d at pH values above 1 1 are reported as being greater than 300,000 because at this pH, the Sr concentration was below the detection limit of the AA unit and a value of 0 1 ppm was used to calculate the K ⁇ It is important to mention that there is typically a large difference between the initial pH of the Sr solutions and equilib ⁇ um pH after exchange. This is due to the hydrolysis of the sodium nonatitanate whose reaction is shown below.
• sample 1-6 was placed on a piece of Whatman filter paper and inserted into a longneck round bottom flask which contained distilled deionized water. The flask was gently heated to produce water vapors which would then impregnate the partially crystalline layered sodium titanate sample. A second portion of sample 1-6 was placed in a 75°C oven until needed. For the K,j measurements, TGA, and XRD pattern of this dried material, the second portion of sample 1-6 was removed from the oven and immediately transferred to the appropriate testing container to help prevent abso ⁇ tion of moisture. The K d measurements were done using a solution containing 5 M NaNO 3 , 1 M NaOH, and 91.67 ppm Sr 2 " " . The results are shown in
• This Example examines the effect of the hydrothermal treatment step on the strontium K,, of a partially crystalline layered sodium titanate.
• Four parameters were studied: method of gel preparation (sol-gel or reflux), concentration of NaOH in the autoclave, the time, and the temperature of the hydrothermal treatment step.
• the source material for the experiments was sodium titanate gel made by the sol-gel method and by the reflux method and made according to Examples 3 and 4.
• the results in Table 7 indicate that the strontium K d 's for partially crystalline sodium titanates prepared by hydrothermally treating amorphous sodium titanates are two times greater for mate ⁇ al treated at 160°C for 5 hours than at 200°C for 20 hours.
• the most statistically significant hydrothermal treatment variable affecting the 24 hour K d data is the relationship between the concentration of NaOH and the temperature during the hydrothermal treatment step. Control of both of these parameters is necessary to fine tune the crystallinity of the final product.
• Example 5 the strontium K d of partially crystalline sodium titanate prepared in Example 5 was evaluated.
• Batches 1 and 2 which were hydrothermally treated for the longest period of time, (160-200° C for 20 hours), were the most crystalline, as indicated by the low full width at half maximum of the largest peak in their X-ray pattern. These most crystalline materials also have the lowest K d 's because high crystallinity hinders the interlayer diffusion, thereby lowering strontium uptake.
• the sodium titanate from all four batches have a high strontium K ⁇ . But the strontium K d for the batches hydrothermally treated for 5 hours are about two times higher than for the batches treated for 20 hours (20,500 vs. 1 1 ,500 mL/g). This difference may be correlated with the degree of crystallinity of the samples.
• Figure 8 is a plot of the strontium Kj of the batches as a function of FWHM (full width at half maximum peak height of the 001 reflection peak).
• the X-ray pattern for batch 2 shows a major peak at 8.76 angstroms. This peak is still present after stirring the sample with 0. 1 M NaOH. By this observation, the new peak is not a H 4 Ti ⁇ ,O 20 phase (which should result if the sample were washed with too much water in the pilot plant).
• Batch 2 may contain another sodium titanate phase, possibly Na ? Ti,O 7 which has its major peak at 8.270 angstroms. All other batches contain only nonatitanate.
• Figure 9 shows that batch 2 has the longest period at the internal temperature of 200°C (18 hours). This extended heating period may have allowed the new phase to form.
• Figures 10A, B, C, and D show scanning electron micrographs (SEM) of each of the pilot plant batches at 3000 times magnification.
• mixing does not affect the resulting strontium K,,, it does influence the gross morphology of the exchanger.
• Mixing the gel during hydrothermal treatment causes shear stresses in the newly forming sodium titanate, which in turn results in a higher number of loose fibers and elongated bundles.
• This example details a method for preparing an amorphous sodium titanate bound crystalline sodium titanate.
• TiP titanium isopropoxide
• This example details the preferred method for preparing an titania bound partially crystalline sodium titanate.
• TiP titanium isopropoxide
• the mixture was agitated until it formed a thick paste.
• the paste was subsequently spread on a Teflon sheet and air-cured for 45 minutes. After air-curing, the plaque was cured in the oven at 85 °C overnight.
• the cured plaque was ground with a mortar and pestle, then sieved to obtain 20-40 mesh particles.
• the resulting compound is a partially crystalline sodium titanate bound with an amorphous titania.
• the regeneration of the exchanger was achieved by passing 15 mL of a 0.5 M HCl solution through the column at a rate of 0.5 b.v./hr and then subsequent treatment with 20 mL of a solution containing 5 M NaOH, and 0. 15 M KCl (0.5 b.v./hr) to give a regenerated partially crystalline sodium titanate.
• the breakthrough curve for Sr sorption is shown in Figure 1 1.
• the curve shows that the partially crystalline sodium titanate effectively purifies approximately 700 column volumes, (cv.), of the model solution in the first sorption cycle, and after regeneration, the material purifies nearly twice the number of c.v. 's ( 1200) in the second cycle.
• Pellets of sodium titanate prepared by the method of Example 5 combined with Portland cement and calcium aluminate (Ciment Fondu) were prepared according to the method of Example 11 , based on the recipe set forth in Table 9, below.
• This Example describes methods of introducing porosity into the inorganic binder/ion exchanger system to improve mass transfer.
• mass transfer of cations into the exchanger increases and therefore increases the amount of radioactive cation captured.
• Two methods investigated for increasing porosity were gas foaming of the binder-exchanger and addition of inert fillers to the binder-exchanger system. The inert filler was leached out to form porous pellets. All samples using pore formers were prepared by using the general procedure listed in Example 15.
• One aluminum filled porous sample was sent for surface area determination via nitrogen porosimetry and exhibited a Langmuir surface area of 1 1 1. 1 m /g, a BET surface area of 63.2 m 2 /g, and an average pore radius of 32.2 angstroms.
• the aluminum filler increased both the BET and Langmuir surface areas in the bound samples to surface areas similar to that seen in the unbound sodium titanate. Even with the increased surface area, the Sr-K d for this sample was small.
• inorganic or organic fillers were blended and cured with the binder-exchanger system described in Example 1 1.
• the inorganic fillers were calcium carbonate and calcium sulfate while the organic filler was a low molecular weight hydrocarbon wax. These fillers have low solubility in water but can be leached out with the appropriate leaching solutions.
• Organic pore formers were used to increase porosity without introducing additional calcium to the system.
• the organic pore formers were added into the system at different volume percent loading as listed in Table 13. There was no increase in K ⁇ as the porosity due to leached wax increased.
• the strontium K d did increase with increased exchanger loading for samples 16- 13 and 16-14. This was also observed with the inorganic fillers. There appears to be an upper limit to the amount of exchanger that can be added without loss of mechanical strength.
• the K j values were again lower than the virgin sodium titanate powder. TABLE 13
• cement or calcium exchanged bound sodium titanate can be fully regenerated with an acid wash followed by a caustic wash. However, when the acid wash was tested on cement or calcium exchanged, cement bound sodium titanate, the pellet broke apart, indicating acid attack on the binder.
• the untreated sample, the acid washed sample, and the 0.1 M NaOH treated sample all have nearly the same strontium uptake (K d between 161-264 mL/g based on sodium titanate weight within the pellet).
• the strontium uptake of the sample regenerated with the 2 M NaOH was 3.9 times higher than the o ⁇ ginal sample (623 vs 161 mL/g)
• the low K d of the regenerated bound sample with respect to the virgin sodium titanate powder (623 vs. 10,000 mL/g) probably indicates that mass transfer within the pellet must be improved by increasing the porosity.
• sodium titanate gel was tested as a binder for partially crystalline sodium titanate and found to have good mechanical strength, is resistant to caustic, and enhances the strontium uptake of sodium titanate. Since the sodium titanate gel is inorganic, this binder will have a high resistance to damage by radiation.
• Sodium titanate as prepared in Example 5 was bound with sodium titanate gel by two different methods.
• the binder was formed by making a sodium titanate sol-gel (methanol, NaOH, and titanium isopropoxide) and adding the sodium titanate exchanger before curing.
• titanium isopropoxide (TiP) was mixed with the sodium titanate ion exchanger and allowed to solidify in moist air before curing.
• Table 14 summarizes the effectiveness of titanate as a binder for sodium titanate with respect to ion exchange capacity and mechanical strength. Bound samples passed the mechanical test if they withstood being shaken for 24 hours in solutions containing 64 ppm Sr, 5 M NaNO 3 , and 0. 1 M NaOH (marked as “P” in Table 14). Those that failed are designated by "F” .
• This example details the measurement of strontium equilibrium batch capacities for titania bound Na-titanate prepared according to Example 13, as well as each of the unbound pilot plant batches prepared in Example 5.
• the 24-hour K ⁇ of titania bound sodium titanate is 3.5 times higher than powder (37,000 vs. 10,800 mL/g for 64 ppm Sr, 5.1 M NaNO 3 , and 0. 1 M NaOH).
• the capacity of the TiP-bound sodium titanate is nearly the same as for the unbound material (batch 2). Because the presence of the titania binder does not affect capacity, the binder itself may take up strontium.
• K d measurements of the titania binder indicates that this is the case, with a K d of 17,000 mL/g (64 ppm Sr, 5. 1 M NaNO 3 , 0. 1 M NaOH).
• the powder combined with the binder has a higher strontium uptake than the powder of the binder by itself.
• the titania binding process produces a composite mate ⁇ al which has enhanced mass transfer.
• This Example details a method for manufacturing sodium titanate ion exchange pellets using an organic binder with introduced porosity to improve mass transfer inside the pellet.
• Partially crystalline sodium titanate powder produced in Example 5 had a Sr 2 * distribution coefficient (Kj) of 16900 mL/g.
• the sodium titanate powder was subsequently bound with 20 wt % cellulose acetate. While Kj testing on the preliminary pellets were positive (K j Ca 2500), later pellets consistently tested low with K d values less than 300. The extreme decrease in K d was due to decreased mass transfer through the cellulose acetate. Incorporating porosity in the pellet using a binder with pore former, consistently recovered the K d to values greater than 1600 mL/g.
• the process to produce pellets with pore former consisted of dissolving cellulose acetate (22.5 wt %) in an acetone (47.5 wt %)/formamide (30.0 wt %) mixture. Pores are formed by a phase inversion of the acetone/formamide/water system when the pellet is later extruded into water.
• the solution was blended with sodium titanate at a weight ratio of 1 :4 cellulose acetate to ion exchanger. Once blended, the mixture was stirred to volatilize enough acetone to leave a thick paste.
• the paste was extruded into a water wash bath containing 0. 1 % Triton XL-80N, 50% glycol and 25% glycerol at 10°C.
• the purpose of the water bath is to leach the formamide/acetone solvent and to minimize the pore collapse due to drying of the membrane.
• the low temperature facilitates the precipitation of the polymer and freezing of the pore structure.
• the surfactant reduces pore collapse upon drying by reducing capillary pressures.
• the reason for the loss of mass transfer upon binding is apparent from Table 16.
• the surface area of virgin sodium titanate is greater than 139 m 2 /g, but the extruded powder blended with cellulose acetate and acetone showed very little surface area ( ⁇ 1 m /g).
• the cellulose acetate had blinded the surface of the sodium titanate powder.
• the surface area increased to greater than 91 m 2 /g.
• the wetability of the pellets using the new binder process also increased. The pellets with pore former wetted more easily due to intact pores and presence of residual surfactant in the pores.
• This example demonstrates that heat treatment increases the mechanical strength of titania bound sodium titanate.
• partially crystalline sodium titanate is mixed with a hydrolyzable titanium compound in air and stirred for about one hour, a paste like material is obtained due to the hydrolysis of TiP to form titania/titanium hydroxide.
• This material was then cured at room temperature in air and then dried at 90°C overnight. After drying the material was ground to below 40 mesh.
• the titania bound sodium titanate powder was compressed in a pelletizer to a piece density of 1.8 - 2.2 g/ml.
• the pellets were then calcined at 200°C, 300°C and 400°C, respectively. After 4 hours of thermal treatment, the pellets were crush tested using the ASTM method D4179.
• the physical properties of the crushed product were combined with product AW-300 zeolite, manufactured by Des Plaines, Illinois, UOP.
• the instrument used was an Instron model 4502 with a 100 Newton load cell. The results are found
• Partially crystalline sodium titanate made according to the method of Example 5 was added to a slurry of hydrous titania. Methyl cellulose was added as organic binder to form the material before calcination. The mixture was extruded and calcined at 560°C for 4 hours. The calcined extnidates exhibited good mechanical strength, but powdered in alkali solution.
• Partially crystalline sodium titanate made using the method described in Example 5 was mixed with titania hydrate powder.
• the mixture was pelleted to a piece density of 1.8 - 2.2 g/ml.
• the pellets were then calcined at 400°C and 560°C, respectively. After 4 hours of thermal treatment, calcined extrudates have reasonably good mechanical strength, but powdered in alkali solution.
• the titania bound sodium titanate powder made using method describing in Example 1 was mixed with titania hydrate powder.
• the mixture was pelleted to a piece density of 1.8 - 2.2 g/ml. the pellets were then calcined at 400°C and 560°C, respectively. After 4 hours of thermal treatment, all the pellets have very good mechanical strength with strong resistance against degradation in alkali solution.
• This example demonstrates a process of making titania bound crystalline sodium titanate pellets using a motorized pellet former, which is facilitated by the presence of a solid lubricant, namely stearic acid.
• a solid lubricant namely stearic acid.
• the titania bound crystalline sodium titanate powder was mixed with 0.5 % - 4% of stearic acid and pelletized with tablet press, Coulton 215, to a piece density of 1.8 - 2.2 g/ml.
• the pellets were then calcined at 400° C either in the air or in air saturated with moisture at room temperature. After 4 hours of thermal treatment, all the pellets have very good mechanical strength with strong resistance against degradation in alkali solution.
• the strontium Kd was measured for three samples: intact pellets; pellets ground to 16-45 mesh; and to below 45 mesh.
• the intact pellets had a K ⁇ of 1 1 ,860 mL/g.
• the 16-45 mesh material has a K d of 1 1 ,531 , and the 45" mesh material had a K d of 12,813.
• titania bound crystalline sodium titanate prepared by the method of Example 13 is used to remove uranium from an aqueous solution.
• This example describes a method for converting partially crystalline sodium titanate into crystalline hydrogen titanate followed by testing the hydrogen titanate as an ion-exchanger.

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