SEPARATION OF COBALT(II) AND NICKEL(II) IONS FROM ACID AQUEOUS SOLUTIONS BY Co IT ION-EXCHANGE INTO γ-TITANIUM PHOSPHATE

ABSTRACT

The Co²⁺-2H⁺, Ni²⁺-2H⁺, and Co²⁺-Ni²⁺-2H⁺ ion exchange processes into γ-Ti(H₂PO₄)(PO₄)2H₂O were studied. Exchange isothenns and titration curves were obtained. Monometallic half ion exchange phases were formed by using MC₂+HCl (M=Co,Ni) solutions. Equilibrium constants, free energy, enthalpy, and entropy of the Co²⁺-2H²⁺ ion exchange reaction were determined. In (Co,Ni)Cl₂ solutions, bimetallic a half ion exchange substitution solid solution is detected. Equilibrium constant of the Co²⁺-Ni²⁺ substitution process in the γ-Ti(Co_xNi_0.5?x.HPO₄)(PO₄)nH₂O phase at 85°C was determined. In (Co,Ni)Cl₂+HCl solutions, total separation of Co²⁺ and Ni²⁺ is obtained.     

Adsorption of Radioactive Ions 137Cs+, 85Sr2+, and 60Co2+ on Natural Magnetite and Hematite

Abstract

Natural magnetite and hematite have been used as granular sorbents for ¹³⁷Cs⁺, ⁸⁵Sr²⁺, and ⁶⁰Co²⁺ at tracer concentration levels in aqueous solutions of constant pH (range 2–10) at 25°C. The kinetics of adsorption, up to the first 60 to 90 min, followed a first-order equation. At pH 6–8 about 50% Cs, 30% Co, and 18% Sr is removed from the solution with magnetite and 78% Co with hematite. The difference in the sorption capabilities of magnetite and hematite is discussed in terms of crystal structures of these oxides.     

SYNTHETIC INORGANIC ION-EXCHANGE MATERIALS. XXXXI. ION EXCHANGE EQUILIBRIA OF ALKALI METAL IONS/HYDROGEN IONS ON TIN(IV) ANTIMONATE

Ion exchange equilibria of alkali metal ions (Li⁺, Na⁺, K⁺,, Rb⁺, and Cs⁺)H⁺, systems have been studied in MNO-j-HNOj media with ionic strength of 0.1 at 30, 45 and 60 °C on tin(IV) antimonate as a cation exchanger. The ion exchange isotherms have been measured for both forward and backward reactions by the batch technique. The isotherms showed S-shaped curves for all exchange systems studied. The selectivity coefficients (logarithmic scale) vary with the equivalent fraction X_M of alkali metal ions in the exchanger and give two linear functions of X_M with a break point (X_M= 0.14, except 0.04 for Li⁺, /H⁺) indicating two different exchanging sites. The selectivity sequence, Na⁺, ? K⁺, ? Rb⁺, ? Cs⁺, ? ? Li, holds in the range of Xu= (0 - 0.04) and the sequence, Cs < Rb ⁺, ? K ⁺, ? Na ⁺, < Li ⁺, applies when X_M is higher than 0.14.

Hypothetical thermodynamic data on “zero loading” of the ion exchange reaction was evaluated.     

SELECTIVE UPTAKE OF CESIUM BY AMMONIUM TUNGSTOPHOSPHATE (AWP) - CALCIUM ALGINATE COMPOSITES

ABSTRACT

The fine crystals of ammonium tungstophosphate (AWP) exchanger were immobilized in the biopolymer consisting of calcium alginate (CaALG) gels. The uptake rate of Cs⁺ for the AWP-CaALG composite was fairly fast and the uptake percentage of Cs^? was above 90 % within 30 min even in the presence of 5 M HNO₃ In a wide HNO₃concentration region of 0.1 - 5 M, the distribution coefficient of Cs^? for the composite was about 10⁴ cm³/g, while those for other nuclides, Na⁺, Sr²⁺, Co²⁺, Eu³⁺ and Am³⁺, were less than 10 cm³/g. The uptake of Cs⁺ followed a Langmuir-type adsorption equation, and the maximum uptake capacity of Cs⁺ increased with the content of AWP immobilized in the composite. The trace amounts of ¹³⁷Cs in the presence of 5 M NaNO₃-l M HNO₃ were selectively adsorbed on the composite column. The AWP-CaALG composite proved to be effective for the selective removal of radioactive cesium from waste solutions containing HNO₃ and NaNO₃     

Ion Exchange of the Organometallic Aqua‐Ion fac‐[99mTc(CO)3(H2O)3]+ from Aqueous Solutions

Dynamic (column) studies on the ion exchange of triaquatricarbonyltechnetium(I) cation, fac‐[^99mTc(CO)₃(H₂O)₃]⁺ (1), in the system: amphoteric ion exchange resin (Purolite S‐950) ‐ aqueous HNO₃ solutions (0.05–2 M) corroborate the +1 charge of 1. Stability constants of fac‐[^99mTc(CO)₃(H₂O)_3?nCl_n]^1?n complexes, determined from the distribution coefficients in the system anion exchanger (Dowex 1X4) ‐ aqueous HCl solutions (0.1–12 M) differ from the literature values determined at a constant ionic strength. This difference, resulting from the decrease in the activity of water with increasing HCl concentration, may be a measure of the effect of non‐constant ionic strength on ion‐exchange equilibria. Weak acidic properties of 1 in aqueous solution at n.c.a. (no carrier added) level (pK_a ?9) have been demonstrated by paper electrophoresis.     

LITHIUM-ION SIEVE PROPERTY OF λ;-TYPE MANGANESE OXIDE

The adsorptive properties of A-Mn0₂for mono and divalent metal ions were investigated by pH titration and by measurements of the distribution coefficients(Kd's) of the metal ions. The pH titration curve showed an apparently monobasic acid type for a H⁺-Li⁺exchange. Those for H⁺-K⁺and H⁺-Cs⁺exchanges were nearly the same as that for blank titration. The lithium ion uptake increased with increasing solution pH and reached 5 meq/g at pH 11. X-ray diffraction analyses showed that the adsorption of lithium ions caused an increase in the lattice constant of a cubic unit cell. The potassium and cesium ion uptakes were nearly zero over a pH range between 4 and 11. A-Mn0₂showed a remarkably high Kd value for lithium ions, compared to a cation exchange resin. The selectivity sequences were Na⁺< K⁺< Rb⁺< Cs⁺<< Li⁺for alkali metal ions, Mg²⁺< Ca²⁺< Sr²⁺< Ba²⁺for alkaline earth metal ions, and Ni²⁺< Zn²⁺< Co²⁺< Cu²⁺for transition metal ions.     

Uptake of cesium and strontium cations by potassium-depleted phlogopite

Phlogopite mica was equilibrated with 1.0 N sodium chloride (NaCl)–0.2 N sodium tetraphenylborate (NaTPB)–0.01 M disodium ethylenediaminetetraacetic acid (EDTA) solution at room temperature resulting in an almost complete removal (92%) of the mica's interlayer K. X-ray powder diffraction analysis provides additional evidence that hydrated Na⁺ ions had almost completely replaced the interlayer K⁺. Following equilibration, the c-axis spacing of the mica increased from 10.0 Å to approximately 12.2 Å. Cesium and Sr ion exchange isotherms indicate that K-depleted phlogopite is highly selective for both elements, the Cs⁺ exchange capacity is 1.26 meq/g or 65% of the theoretical cation exchange capacity and the Sr²⁺ exchange capacity is 1.94 meq/g or 100% of the theoretical exchange capacity of the mica. Kielland plots indicated that the mica was selective for Cs⁺ when the equivalent exchange capacity of Cs⁺ in the exchanger phase (X¯_Cs) was < 0.66 and selective for Sr²⁺ when X¯_Sr < 0.41. At equivalent fractions greater than these levels, layer collapse and/or steric effects limit the diffusion of these ions into the interlayers of the mica. Analysis of the Cs⁺ equilibrated mica utilizing XRD indicated that a collapse of the c-axis spacing had occurred. Based on the high selectivity of < 45-μm K-depleted phlogopite for Sr²⁺ and Cs⁺, this material may prove useful as an inorganic ion exchanger for these radioactive isotopes.     

Ion exchange resins from phenol/formaldehyde resin‐modified lignin

Phenol/formaldehyde resin, commonly sulfonated, is used as ion exchanger. Lignin, which is the phenolic polymer matrix in wood, was isolated from olive stone biomass by alkaline hydrolysis of weak ether bonds (Kraft lignin, KRL). It was then hydroxymethylated (KRLH) with an aqueous solution of formaldehyde. Novolac resin (N) was synthesized from phenol and formaldehyde under acidic conditions. KRL or KRLH was incorporated into phenol/formaldehyde during polymerization (N‐KRL, N‐KRLH). The products of polymerization (N, N‐KRL and N‐KRLH) were sulfonated with concentrated H₂SO₄ (1:3 w/w as typical proportion according to literature or 1:6 w/w as an excess of H₂SO₄) and then cross‐linked with formaldehyde. The different products were characterized by IR spectroscopy, swelling in ethanol, acetone and in an aqueous solution of 1 N NaOH. The ion‐exchange capacity, the moisture retention capacity and the titration curves of the sulfonated and cured products were determined. The ion‐exchange capacity and the uptake of metal ions (mainly Co²⁺ and Cu²⁺) detected by atomic absorption spectroscopy, on the sulfonated materials, prepared in an excess of H₂SO₄, is higher for N‐KRL and N‐KRLH than for N and it takes place at the same rate or faster. The latter shows a medium acidic behaviour according to the titration curves, in contrast with the sulfonated N‐KRLH and N‐KRL which show a strongly acidic behaviour. © 2001 Society of Chemical Industry     

Ion Exchange Kinetics of Heavy Metal Ions on Organic–Inorganic Composite Cation Exchanger Poly-o-toluidine Zr(IV) Tungstate

To study the ion exchange kinetics of heavy metal ions on the organic–inorganic composite cation exchanger poly-o-toluidine Zr(IV) tungstate, Nernst–Planck was computer simulated. Simulated numerical results for counter ions (Cu, Zn, Cd and Pb) of equal valence and four different ionic mobilities are presented to understand the ionic diffusion process. These results are based on the fractional attainment of equilibrium U(τ), of the counter ions under study. The forward (M²⁺–H⁺) and reverse (H⁺–M²⁺) ion exchange processes are justified as the particle diffusion phenomenon. The self-diffusion coefficient (D _o ), energy of activation (E _a ), and entropy of activation (?S*) have also been estimated to understand the ion exchange process occurring over the surface of this cation exchanger and indicated that the ion exchange process is feasible and spontaneous. It is concluded that the difference in activation energies and entropy of activation may facilitate the separation of metal ions. The regeneration capability of this cation exchanger was also explained.     

The Reduction and Oxidation of Co Species in CoZSM-5 Zeolites Studied by IR Spectroscopy

The process of reducing Co ions in zeolite CoZSM-5 by NO, H₂ and CO, as well as of oxidizing them by O₂ was studied by IR spectroscopy with CO as the probe molecule for Co²⁺ and NO as the probe for Co³⁺. Two zeolites of different Co status were used: in the first, Co²⁺ ions were localized mostly in cation exchange positions, and in the second most of the Co²⁺ occurred in the form of CoO and oxide-like clusters. IR studies evidenced that NO reduced some Co³⁺ to Co²⁺ already at room temperature, and also reduced some Co²⁺ to lower oxidation states (probably Co⁺) at 670 and 1070 K. Only Co²⁺ in exchange positions could be reduced with NO. The treatment of zeolite CoZSM-5 with H₂ or with CO at 670 and 1070 K made the reduction of Co³⁺ to Co²⁺ (the contribution of Co³⁺ decreased and the contribution of Co²⁺ increased). IR studies illustrated that the most electron-acceptor Co³⁺ (characterized by a high frequency Co³⁺–NO band) were transformed, by reduction, into the most electron-acceptor Co²⁺ (characterized by a high frequency Co²⁺–CO band). The treatment of zeolite CoZSM-5 with oxygen at 670–1070 K resulted in the oxidation of Co²⁺ to Co³⁺ (the contribution of Co²⁺ decreased while the contribution of Co³⁺ increased).     

Studies on a new heteropolyacid-based inorganic ion exchanger; zirconium(IV) selenomolybdate

A new heteropolyacid-based cation exchanger zirconium(IV) selenomolybdate has been synthesized, characterized using I.R., X-ray, TGA, DTA techniques. Its composition was found to be Zr:Se:Mo::2.5:0.7:1.6 and it is quite chemically stable. It exhibits 0.94 meq/g ion-exchange capacity for Na⁺ ions. Its distribution behavior for 16 metal ions has been studied and its utility has been employed by achieving separations Zn²⁺–Cd²⁺, Zn²⁺–Co²⁺, Ni²⁺–Cd²⁺and Ni²⁺–Co²⁺ on its column.     

THERMODYNAMICS OF ALKALI AND ALKALINE EARTH METAL ION-EXCHANGE ON ZIRCONIUM SULPHOPHOSPHONATES

The thermodynamics of alkali and alkaline earth metal ion exchange on a layered zirconium sulphophosphonate having the general composition Zr(O₃PC₆H₄SO₃H) _×(HPO₄) _2?× yH₂O have been investigated. Enthalpy and entropy changes accompanying the M²⁺ - H⁺ exchange (M = Na⁺, Cs⁺, Mg²⁺ and Ba²⁺)were determined by the temperature variation method. For the monovalent ions, Na⁺ and Cs⁺, the enthalpy terms favor exchange whereas the entropy terms are unfavorable. In contrast, for the divalent ions, Mg²⁺ and Ba²⁺, the exchange is due to highly favorable entropy terms.     

Two-Phase Calorimetry. II. Studies on the Thermodynamics of Cesium and Strontium Extraction by Mixtures of H+CCD− and PEG-400 in FS-13

Abstract

Thermochemical characterization of the partitioning of cesium and strontium from nitric acid solutions into mixtures of the acid form of chlorinated cobalt dicarbollide (H⁺CCD^?) and polyethylene glycol (PEG-400) in FS-13 diluent has been completed using isothermal titration microcalorimetry and radiotracer distribution methods. The phase transfer reaction for Cs⁺ is a straightforward (H⁺ for Cs⁺) cation exchange reaction. In contrast, the extraction of Sr²⁺ does not proceed in the absence of the co-solvent molecule PEG-400. This molecule is believed to facilitate the dehydration of the Sr²⁺ aquo cation to overcome its resistance to partitioning. The phase transfer reactions for both Cs⁺ and Sr²⁺ are enthalpy driven (exothermic), but partially compensated by an unfavorable entropy. The results of the calorimetry studies suggest that the PEG-400 functions as a stoichiometric phase transfer reagent rather than acting simply as a phase transfer catalyst or phase modifier. The calorimetry results also demonstrate that the extraction of Sr²⁺ is complex, including evidence for both the partitioning of Sr(NO₃)⁺ and endothermic ion pairing interactions in the organic phase that contribute to the net enthalpic effect. The thermodynamics of the liquid-liquid distribution equilibria are discussed mainly considering the basic features of the ion solvation thermochemistry.     

Microbial interactions with caesium—implications for biotechnology

The continuing release of caesium isotopes into the environment has highlighted the necessity for efficient removal of Cs from industrial waste effluents prior to discharge. Existing technologies, e.g. zeolite ion-exchange for Cs removal, can be expensive and microbial metal adsorption/accumulation may represent a cheap alternative. The distinct chemical properties of Cs⁺, which dictate a high degree of metabolism-dependent uptake via monovalent cation transport systems, indicate that different approaches are required for biological Cs removal to those which are generally adopted for other metals/radionuclides. The low toxicity of Cs⁺ eliminates one potential problem in the use of live cells for Cs removal. High levels of Cs⁺ accumulation have been reported in a number of microorganisms, but uptake levels vary markedly in different organisms and are strongly influenced by a number of physico-chemical and mechanical parameters, e.g. the use of batch or continuous-flow systems, biomass immobilization (which tends to increase Cs⁺ adsorption at the expense of metabolism-dependent accumulation), pH and particularly the prevalence of other monovalent cations such as K⁺ and Na⁺. Inherent differences in Cs⁺ uptake capacities of different microorganisms appear to be largely attributable to differences in the affinity of monovalent cation transport systems for Cs⁺. The application of rigorous screening procedures involving the use of autoradiography has great potential for isolation of microorganisms with particularly high affinities for Cs⁺. Alternatively, manipulation of the physiological status of microorganisms can dramatically alter the transport of Cs⁺ and other monovalent cations. Hyper- and hypo-osmotic shock, respectively, have so far proved to be the most successful treatments for stimulating Cs removal and recovery. Other manipulations, at both the cellular and molecular level, which are known to influence K⁺ fluxes but have yet to be characterized for Cs⁺, are outlined here.     

Adsorption of Co2+ and Cs1+ by polyethylene membrane with iminodiacetic acid and sulfonic acid modified by radiation‐induced graft copolymerization

Two modified hollow fiber membranes, the chelating hollow fiber membrane with iminodiacetic acid and the cation‐exchange hollow fiber membrane with sulfonic acid group ( SO₃H), were prepared by radiation‐induced grafting of glycidyl methacrylate onto polyethylene hollow fiber membrane and its subsequent iminodiacetation and sulfonation. The adsorption characteristics of Co²⁺ and Cs¹⁺ for the 2 hollow fiber membranes were examined when the solutions of Co²⁺ and Cs¹⁺ permeate across the 2 membranes, respectively. Without regard to the chelating membrane with iminodiacetic acid group and the cation‐exchange membrane with sulfonic acid group ( SO₃H), 2 membranes were observed to adsorb Co²⁺ higher than Cs¹⁺. The adsorption curves of Co²⁺ by IDA group‐chelating fiber membrane in the presence of Na¹⁺ and Ca²⁺ showed that the chelating hollow was found to have a very high selectivity for Co²⁺, even though there is a high concentration of Na¹⁺ and Ca²⁺ in the inlet solution. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 999–1006, 1999     

Rapid Separation of Tl+ and Pb2+ from Various Binary Cation Mixtures Using Dicyclohexano-18-crown-6 Incorporated into Emulsion Membranes

Abstract

Relative transport rates of metal cation nitrates (Na⁺, K⁺, Rb⁺, Cs⁺, Ag⁺, Tl⁺, Ca²⁺, Sr²⁺, Ba²⁺, and Pb²⁺) in a water-toluene-water emulsion membrane system were measured. The toluene component contained the surfactant Span 80 and the crown ether dicyclohexano-18-crown-6. The aqueous receiving phase contained Li₄P2O₇. When each metal cation was individually present in the aqueous source phase, metal extraction was complete within 10 min with the order of extraction being Tl⁺ > Cs⁺ > Ag⁺ > Rb⁺ > K⁺ ≥m Na⁺ and Pb⁺ > Ca²⁺ > Sr²⁺ > Ba²⁺ for uni-and bivalent cations, respectively. Significant extraction was found for all cations except Na⁺, K⁺, and Ba²⁺. Some metal ions were concentrated nearly 10-fold in a 10-min period. Relative transport rates were determined when binary cation mixtures of either Tl⁺ or Pb²⁺ were present at equal concentrations with each of the remaining metal ions in the source phase. Tl⁺, when present with either Na⁺, Cs⁺, or Rb⁺, was selectively extracted from the source phase. Complete and nearly exclusive extraction of Pb²⁺ was observed in the presence of all cations including Tl⁺. The enrichment ratios of Pb²⁺ in the binary mixtures were approximately 10 while those of the second cation were less than 0.5 except for Sr²⁺ which was 0.86. Corresponding separation factors for Pb²⁺ ranged from 1000 to > 6000.     

Removal of Cs1+, Sr2+ and Co2+ from aqueous solutions by adsorption on natural clinoptilolite

The adsorption properties of local clinoptilolite (Serbia) towards Cs⁺, Co²⁺, and Sr²⁺ were investigated by batch equilibration technique. The influence of equilibration time, initial metal cation concentration, solution pH and presence of EDTA on these properties was studied and discussed. Kinetic data were found to be well fitted with pseudo-second order kinetic model. Cs⁺ is preferably adsorbed by the natural clinoptilolite, followed by Sr²⁺ and Co²⁺. The Langmuir adsorption isotherm was used to determine the adsorption capacities from both single and mixed metal solutions. At pH range of 3–12 the adsorption of Cs⁺ remains almost constant, while at low pH (2–3) the adsorption is lesser. At initial pH range of 2–10 adsorption of Sr²⁺ remains approximately stable, whereas at initial pH > 10 adsorption increases significantly. The adsorption of Co²⁺ is low at low pH but increased remarkably with increasing pH and precipitated at pH > 8. Cs⁺ adsorption on the clinoptilolite was not affected by the presence of EDTA, while the presence of EDTA hinders the adsorption of Co²⁺ and Sr²⁺ on clinoptilolite.     

Kinetics of Exchange of Cs+, Co2+ and Sr2+ on Synthetic Hydrous Titanium Oxides

Abstract

In the present work, a study of the kinetics of adsorption of Cs⁺, Co²⁺, and Sr²⁺ on four hydrous titanium oxides, prepared in different media, and designated as Ti‐I, Ti‐II, Ti‐III, and Ti‐IV, was carried out. In the aqueous medium, the internal diffusion coefficients, D_i for Cs⁺ were found to be equal to 3.7×10^?9, 3.7×10^?9, 2.3×10^?9, and 1.5?10^?9 cm²/s, in Ti‐I, Ti‐II, Ti‐III, and Ti‐IV, respectively. For Co²⁺ and Sr²⁺, these values are equal to 0.96×10^?9 and 0.64×10^?9 cm²/s, respectively for Ti‐IV. In Ti‐IV, D_i for all ions generally increases on adding methanol or propanol. This is probably due to greater dehydration, leading to faster ion diffusion, and, hence, to a decrease of ion mobility due to stronger interaction with the surface. In all media in Ti‐IV, the order: D_i(Cs⁺)>D_i(Co²⁺)≥D_i(Sr²⁺) was found which is due to a stronger interaction of the bivalent ions with the exchange sites.     

In situ immobilization properties and mechanism of geopolymer microspheres after adsorbing Sr2+ and Cs+ (Sr/Cs@GPMs)

Herein, in situ immobilization properties and mechanism of the pre-prepared geopolymer microspheres after adsorption of Sr²⁺/Cs⁺ (Sr/Cs@GPMs) were studied. The Sr²⁺ and Cs⁺ were solidified via calcination and a GP slurry coating strategies. The conditions for leaching experiments were H₂O, 0.1 mol/L (NaCl, NaOH, and HCl). The calcination results showed that the pore volume of the two adsorbents gradually decreased with increasing temperature and the order of leaching rate of Sr²⁺/Cs⁺ in calcination of Sr/Cs@GPMs was: HCl > NaCl > NaOH > H₂O, while the leaching rate decreased with increasing temperature and met the national standards. The in situ immobilization mechanism revealed that the pores of the adsorbent disappeared after high-temperature calcination or ceramic reaction. The results of the GP slurry coating experiment showed that the leaching rates of Sr²⁺/Cs⁺ decreased with leaching cycles. The solidified slag-based GP with Sr/Cs@GPMs (12%) adsorbent in 0.1 mol/L HCl leaching environment had the 28-day leaching rate (R₂₈) and cumulative leaching fractions (P₂₈) for Sr²⁺ of 1.26 × 10^-3 cm/d and 0.057 cm, respectively, and 1.51 × 10^-3 cm/d and 0.127 cm for Cs⁺, respectively. These metrics met the requirements of the national standard, thus indicating that slag-based GP has value in treating radionuclides.     

Recovery of purified radiocesium from acidic solution using ammonium molybdophosphate and resorcinol formaldehyde polycondensate resin

Separation of Cs⁺ from acidic solution was investigated using ammonium molybdo- phosphate (AMP) based sorbents. Four sorbents including two AMP powders and two composites prepared by coating of AMP powder on polymethylmethacrylate (PMMA) beads were used in this study. Equilibrium sorption isotherms for Cs⁺ on AMP sorbents were determined. The effect of H⁺ concentration on Cs⁺ uptake by AMP–PMMA beads was examined. Two column runs were carried out to establish the Cs⁺ separation performance of AMP–PMMA beads from 1.0 M nitric acid having Cs⁺ concentration equivalent to 10 Ci of ¹³⁷Cs per litre. Recovery of Cs⁺ from loaded AMP–PMMA column was carried out by dissolution of AMP using NaOH solution. The feasibility of ion exchange purification of the recovered Cs⁺ solution was examined using resorcinol formaldehyde polycondensate resin (RFPR). The Cs⁺ sorption isotherm on RFPR from Cs-bearing dissolved AMP solution was determined. Purification of Cs⁺ from dissolved AMP solution was studied in two column runs using RFPR in loading-elution cycles. The results of these studies are useful in formulating a scheme for the recovery of purified ¹³⁷Cs product from high level waste for large-scale utilization as a radiation source in industrial irradiators.