Chlorinated Cobalt Dicarbollide Research Articles

Experience of Mastering, Industrial Exploitation, and Optimization of the Integrated Extraction–Precipitation Technology for Fractionation of Liquid High-Activity Wastes at Mayak Production Association

Results are presented of tests, mastering, industrial exploitation, and optimization of an integrated scheme for fractionation of liquid high-activity wastes (HAWs) produced in processing of spent nuclear fuel (SNF), which includes the extractive recovery of the Cs–Sr with the system based on chlorinated cobalt dicarbollide in a heavy fluorinated diluent and extraction from the resulting raffinates of a group of rtansplutonium and rare-earth elements by the oxalate precipitation method. This was done at Mayak Production Association in 1996–2003. A total of more than 1600 m3 of HAWs that were stored during a long time in storage facilities and contain more than 54 MCi of β- emitters. About 52 MCi of β- and also about 0.5 MCi of α-nuclides were isolated into concentrates and transferred to vitrification. The scale of activities on integrated fractionation of acid HAWs has no analogs in the world.

On the Possibility of Extractive Fractionation of REEs and TPUs from Weakly Acid Raffinate Produced of Irradiated Fuel Elements with a Mixture of ChCD and D2EHPA in Polar Solvent

Laboratory study was performed to examine the extraction of rare-earth elements and americium with a synergic mixture of chlorinated cobalt dicarbollide (ChDC) and di-2-ethylhexyl phosphoric acid (D2EHPA). It was shown that this extractive agent effectively extracts TPEs and REEs from a nitrate solution of highly radioactive wastes and can extract americium into a separate fraction with good purification to removes. The scheme suggested for extractive isolation of TPEs has a number of advantages over the schemes previously taken for verification.

Modified Diamide and Phosphine Oxide Extracting Compounds as Membrane Components for Cross-Sensitive Chemical Sensors

This research is devoted to the development and study of novel cross-sensitive sensors based on modified extracting ligands. According to the previous results of liquid extraction studies, the chemical modification of membrane active components would change the analytical characteristics of a sensor comprising them. The sensing elements of the studied sensors consisted of various derivatives of N,N,N′,N′-tetraoctyldiamide of diglycolic acid (TODGA) and di-phenyl-N,N-di-i-sobutylcarbamoylmethylen phoshine oxide (CMPO) used as neutral carriers, CCD (chlorinated cobalt dicarbollide) as a lipophilic additive, different plasticizers, and poly(vinyl chloride) (PVC) as a polymer. TODGA-based sensors demonstrated a stable and reproducible response towards rare earth cations in acidic media (pH = 2). Changing the concentrations and ratio of neutral carriers and the lipophilic additive, it is possible to modify the sensitivity and selectivity of the sensors towards the same target ions. Bonded ligands, such as cobalt dicarbollide covalently attached to TODGA and CMPO, exhibited lower selectivity and sensitivity to rare earth cations. A possibility to vary the cross-sensitivity patterns of the sensors in a wide range might be of great interest for the development of multisensor systems allowing the simultaneous determination of several analytes in multicomponent solutions.

Treatment of Spent Nuclear Fuel for Separation, Immobilization and Disposal of Heat Generating High Level Fission Products, Caesium and Strontium

Separation of heat generating, high level fission product caesium and strontium from spent nuclear fuel boosts the capacity of waste repositories by as much as fifty times. For efficient use of already scarce repositories, separation of such fission products is mandatory. Separations of caesium and strontium using Chlorinated Cobalt Dicarbollide (CCD), PEG (Polyethylene Glycol), UNEX process and by Calixarenes or Fission Product Extraction Process (FPEX) were discussed. The UNEX method was then proposed as the most feasible method option. Following separation, nuclear waste immobilization techniques for such high-level fission product were discussed. The techniques included usage of concrete, glass and synthetic rock. Among them synthetic rock was identified as the most suitable one for immobilization of high-level nuclear waste. Finally, a safe disposal system with necessary required geology was shown for safe disposal of the waste.Journal of Chemical Engineering, Vol. 30, No. 1, 2017: 37-42

A new approach for selective Cs+ separation from simulated nuclear waste solution using electrodriven cation transport through hollow fiber supported liquid membranes

The present work describes a novel and cleaner approach for large scale (litre) separation of cesium from simulated nuclear waste solutions by electrodriven transport through a hollow fiber supported liquid membrane (HFSLM) containing chlorinated cobalt dicarbollide as the carrier. To the best of our knowledge, this is the first report on electrodriven cation transport through HFSLM. The transport selectivity of Cs+ over Na+ and other fission products was studied from synthetic nuclear waste solutions. An attempt has also been made to pre-concentrate radio-cesium from an environmental sample containing very low level of 137Cs (≤ 10–12M) with excellent transport efficiency. A very high decontamination factor of cesium over Na+ other metal ions have been obtained for all types of feed solution. For neutral feed solution, the current efficiency for the Cs+ transport has been found to be 100%. The present work certainly adds a new dimension to the ongoing membrane based separations.

Electrodriven Transport of Cs+ through Polymer Inclusion Membrane as “Solvent Separated Ions”

In our earlier work, we reported [Env. Sci. Technol. 2014, 48, 12994] a novel electrodialysis based selective separation of Cs+ from nuclear waste solution using chlorinated cobalt dicarbollide (HCCD) loaded polymer inclusion membrane (PIM). In continuation with that work, the mechanism of electrodriven transport of Cs+ through HCCD loaded polymer inclusion membranes has been explored. PIMs containing fixed amount of cellulose triacetate and nitrophenyl octyl ether (NPOE) but different concentrations of the carrier have been prepared. The experimental flux of Cs+ across the PIMs, for two different concentrations of the metal ion in the initial feed solution, has been measured using the radiotracer technique. On the basis of the Nernst–Planck equation, an attempt has been made to calculate the time dependence of concentration changes of the metal ion in the feed compartment. The experimental parameters of the membrane., viz., length, self-diffusion coefficient, distribution ratio, electrical resistance, an...

Synergistic extraction of rare earth elements from HNO3 solutions with a mixture of chlorinated cobalt dicarbollide and acidic zirconium salt of dibutyl hydrogen phosphate in a polar diluent

Extraction of La and Ln(III) (except Pm) from HNO3 solutions with mixtures of acidic zirconium salts of dibutyl hydrogen phosphate (ZS HDBP) with chlorinated cobalt dicarbollide (CCD) in a polar diluent, 1: 1 mixture of о-chloronitrobenzene and CCl4, was studied. A synergistic effect is observed at definite ratios of CCD and ZS HDBP in the mixture. The magnitude of the synergistic effect increases with an increase in the Zr to HDBP molar ratio. The maximal synergistic effect equal to 360 was reached for Dy in the ZS HDBP (1: 6)–CCD extraction system. The maximal REE distribution ratio (Dmax) is observed for elements from La to Dy at the HDBP to CCD molar ratio of 2 in all the extraction systems. For elements of the Ho–Lu series, Dmax is observed at the HDBP to CCD molar ratio from 2 to 6. The HDBP to CCD molar ratio at which Dmax is reached increases with an increase in the Zr content of the extraction system. For some pairs of elements, the separation factor considerably increases in the extractant mixture relative to the extractants taken separately. The largest increase in the separation factor (by a factor of 8.3) was noted for the Tm–Er pair in the CCD–ZS HDBP (1: 6) system. The synergistic effect in some cases is preserved at least up to the HDBP to CCD molar ratio of 670: 1, and at higher ratios the magnitude of the synergistic effect does not exceed the uncertainty of its determination. This fact suggests the formation of so-called hypercomplexes containing tens and hundreds of HDBP molecules in the CCD–ZS HDBP systems, similarly to the CCD–HDBP system. The largest number of HDBP molecules was noted in the Ln–CCD–[(ZS HDBP (1: 6)]n complexes. The CCD–ZS HDBP (1: 6) and CCD–ZS HDBP (1: 12) systems are promising for the separation of REE and TPE, and small addition of CCD to the ZS HDBP (1: 6) system in a polar diluent allows the development of a cheap solvent efficiently recovering all the REE and TPE from a 3 M HNO3 solution.

Partitioning of REE(III) and TPE(III) with an extractant based on chlorinated cobalt dicarbollide and polyethylene glycol

Theoretical principles and practical characteristics are reported for an extraction process for REE and TPE partitioning using an extractant based on chlorinated cobalt dicarbollide (CCD) and polyethylene glycol (PEG). Joint extraction of REE and TPE is performed from a ≤1 M HNO3 solution with a solution of CCD and PEG in a polar diluent. The TPE stripping is performed with an aqueous solution of a complexing agent (diethylenetriaminepentaacetic acid) and an organic base (urea or thiourea). Trials on an extraction rig in Gatchina showed that the process can be successfully used for exhaustive recovery of REE and TPE from real Purex process raffinates and for their subsequent partitioning, with reaching the required process parameters. The results of semicommercial trials of the REE/TPE partitioning process on the extraction installation of the Mayak Production Association are reported. The trials were performed on such scale for the first time in the world. In reprocessing of 40 m3 of high-level raffinates, good results were obtained with respect to the process hydrodynamics, REE/TPE partitioning, and their separation from impurity elements. The process has high potential for use in HLW reprocessing technologies at new radiochemical plants.

Electrodriven selective transport of Cs+ using chlorinated cobalt dicarbollide in polymer inclusion membrane: a novel approach for cesium removal from simulated nuclear waste solution.

The work describes a novel and cleaner approach of electrodriven selective transport of Cs from simulated nuclear waste solutions through cellulose tri acetate (CTA)/poly vinyl chloride (PVC) based polymer inclusion membrane. The electrodriven cation transport together with the use of highly Cs+ selective hexachlorinated derivative of cobalt bis dicarbollide, allows to achieve selective separation of Cs+ from high concentration of Na+ and other fission products in nuclear waste solutions. The transport selectivity has been studied using radiotracer technique as well as atomic emission spectroscopic technique. Transport studies using CTA based membrane have been carried out from neutral solution as well as 0.4 M HNO3, while that with PVC based membrane has been carried out from 3 M HNO3. High decontamination factor for Cs+ over Na+ has been obtained in all the cases. Experiment with simulated high level waste solution shows selective transport of Cs+ from most of other fission products also. Significantly fast Cs+ transport rate along with high selectivity is an interesting feature observed in this membrane. The current efficiency for Cs+ transport has been found to be ∼100%. The promising results show the possibility of using this kind of electrodriven membrane transport methods for nuclear waste treatment.

A highly efficient solvent system containing chlorinated cobalt dicarbollide in NPOE—Dodecane mixture for effective transport of radio-cesium from acidic wastes

The present paper is a first time report on the pertraction of radio-cesium (137Cs) across a flat sheet supported liquid membrane (FSSLM) containing a solvent system containing chlorinated cobalt dicarbollide (CCD) in a diluent mixture containing 2-nitrophenyloctyl ether (NPOE) and n-dodecane. The feed phase consisted of 1M HNO3 while 8M HNO3 was the receiver phase. The optimized solvent system with 1.0×10−2M CCD in 60% NPOE+40% n-dodecane was found to be highly efficient for the transport of the metal ion in terms of metal ion extraction (87.8%) and stability of the liquid membrane. The transport efficiency decreased with increasing feed phase HNO3 concentration suggesting applicability of the transport system for radioactive wastes at low to moderate acidity (≤1M HNO3). Furthermore, the transport rates of Cs(I) increased with increasing CCD concentration suggesting direct involvement of the carrier molecule in the metal ion transport. The addition of PEG-400 (used for Sr(II) transport) into the solvent system did not result in the expected co-transport of Sr(II) which was attributed to the leaching out of the ligand from the membrane pores due to its high aqueous solubility. The diffusion coefficient was calculated by the lag time method and was found to be 1.7×10−7cm2/s which was somewhat lower than that obtained by Danesi׳s method.

Evaluation of a novel and efficient solvent system containing chlorinated cobalt dicarbollide for radio-cesium recovery from acidic wastes

Abstract A novel solvent system containing chlorinated cobalt dicarbollide (CCD) in a diluent mixture containing 2-nitrophenyloctyl ether (NPOE) and n-dodecane was found to be highly efficient for the extraction of radio-cesium from acidic feed conditions. When PEG-400 (polyethylene glycol with average molecular weight of 400) was added to the solvent system, it was found to extract radio-strontium as well similar to that reported with the UNEX (Universal Extractant) solvent. The solvent system was found to be superior as compared to analogous solvent systems reported previously using CCD in either nitrobenzene or PTMS (phenyltrifluoromethyl sulphone, a fluorinated diluent). The present work deals with less toxic solvent formulation which can be used as an alternative to these hazardous/toxic chemicals for simultaneous recovery of Cs(I) and Sr(II) from acidic solutions. Batch co-current extraction data are also presented for the simultaneous recovery of Cs and Sr which indicated near quantitative extraction (>99.5%) of the metal ions in 4 and 3 stages, respectively. The reusability and radiolytic stability studies were also carried out which suggested highly encouraging results.

Simultaneous extraction of Cs and Sr from synthetic high level waste solutions using a solvent containing chlorinated dicarbollide and PEG-400 in PTMS

A Cs selective solvent composed of 0.08 M chlorinated cobalt dicarbollide and 0.5 % PEG 400 (polyethylene glycol of average molecular weight of 400) in phenyl trifluoromethyl sulphone (PTMS) was used for the extraction of Cs(I) and Sr(II) from nitric acid solution as well as synthetic pressurized heavy water reactor (PHWR) high level waste (HLW) solution. Comparison was also done with analogous solvent system in nitrobenzene and xylene diluent mixture. The various experiments included acid concentration variation and PEG-400 concentration variation. A sharp decrease in the Cs(I) and Sr(II) extraction was noticed with increasing nitric acid concentration. On the other hand, while PEG-400 concentration variation had very little effect on Cs(I) extraction, it has a very significant influence on Sr(II) extraction. Batch co-current extraction studies were carried out with solvents made from both the diluent systems and the results indicated that PTMS based solvent system was superior to that containing nitrobenzene and can be used for the recovery of the metal ions from actual PHWR-HLW. Radiolytic degradation studies were also carried out and the results suggested reasonably good stability of the solvent system.

Synergistic extraction of rare earth elements from HNO3 solutions with a mixture of CCD and HDBP in a polar diluent

The extraction of Ln(III) (except Pm), La(III), and Y(III) from HNO3 solutions with dibutyl hydrogen phosphate (HDBP), chlorinated cobalt dicarbollide (CCD), and their mixture in a polar diluent, mixture of o-chloronitrobenzene (OCNB) and CCl4 (1: 1), was studied. A synergistic effect is observed for all the examined elements. For the series La-Dy, it reaches a maximum at the HDBP to CCD molar ratio of 3: 1, and for the series Tb-Lu, at the HDBP to CCD molar ratio of 9: 1. The synergistic effect is observed at the HDBP to CCD molar ratios of up to 700: 1 and 1500: 1 for heavy and light lanthanides, respectively. At higher ratios, the magnitude of the synergistic effect does not exceed the uncertainty of its determination. This fact indicates that one CCD molecule can activate several hundreds of HDBP molecules, enhancing their extraction ability. The degrees of separation of neighboring lanthanides do not noticeably change on introducing CCD into the extraction system. The key component of the hypercomplex is the CCD anion, with the role of the CCD proton being insignificant. A complex of variable composition, containing lanthanide, CCD, and HDBP, is formed in the organic phase.

Extraction of Lanthanoids with Diamides of Dipcolinic Acid from Nitric Acid Solutions. II. Synergistic Effect of Ethyl-Tolyl Derivates and Dicarbollide Cobalt

New ethyltolyl-substituted derivatives of dipicolinic acid, N,N-diethyl-N',N'-ditolyl diamides (DPA) have been synthesized and evaluated for their extraction capability toward americium and lanthanides. These diamides were studied as a stand-alone extractant in conjunction with a polar solvent FS-13 (trifluoromethylphenyl sulfone) as well as in an extraction mixture in conjunction with the synergistic extractant chlorinated cobalt dicarbollide and FS-13. The effect of the ortho-, meta-, and para position of the methyl group on the tolyl ring of the N,N'-diethyl-N,N'-ditolyl-diamide (EtTDPA) was investigated. Data on the extraction ability of different diamides of dipicolinic acid show that the Et(o)TDPA has the most promising properties because it has the best balanced selectivity between the heavy and light lanthanoids.

Characterization of high level waste for minor actinides by chemical separation and alpha spectrometry

The high level waste (HLW) generated from the reprocessing of the spent fuel of pressurized heavy water reactor has been characterized for the minor actinides. The radiation dose of the waste solution was reduced by radiochemical separation of cesium from HLW by solvent extraction with chlorinated cobalt dicarbollide dissolved in 20% nitrobenzene in xylene. Minor actinides (Np, Pu, Am, Cm) in the high level waste were assayed by alpha spectrometry following radiochemical separation. The gross alpha activity determined by liquid scintillation agrees well (within 10%) with the cumulative quantities of actinides determined by alpha spectrometry.

Separation of Transmutation- and Fission-Produced Radioisotopes from Irradiated Beryllium

The primary objective of this study was to test the effectiveness of a two-step solvent extraction-precipitation process for separating transmutation and fission products from irradiated beryllium. Beryllium metal was dissolved in nitric and fluoroboric acids. Isotopes of 241Am, 239Pu, 85Sr, 60Co, and 137Cs were then added to make a surrogate beryllium waste solution. A series of batch contacts was performed with the spiked simulant using chlorinated cobalt dicarbollide and polyethylene glycol diluted with sulfone to extract the isotopes of Cs and Sr. Another series of batch contacts was performed using a combination of octyl (phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide in tributyl phosphate diluted with dodecane for extracting the isotopes of Pu and Am. The 60Co was separated by first forming a cobalt complex and then selectively precipitating the beryllium as a hydroxide. The results indicate that >99.9% removal can be achieved for each radionuclide. Transuranic isotope contamination levels are reduced to <100 nCi/g, and sources of high beta-gamma radiation (60Co, 137Cs, and 90Sr) are reduced to levels that will allow the beryllium to be contact handled. The separation process may be applicable to a recycle or waste disposition scenario.

Removal of Cs from simulated high-level waste solutions by extraction using chlorinated cobaltdicarbollide in a mixture of nitrobenzene and xylene

Efficacy of chlorinated cobaltdicarbollide in a modified diluent, 20% nitrobenzene in xylene was tested for the extraction and recovery of Cs from simulated high-level waste (HLW) solutions generated from PHWR-fuel reprocessing. Concentration of the reagent, composition of the diluent, numbers of contacts, the nature of stripping agents are some of the parameters optimized for the complete removal of Cs from such waste solutions. The above solvent extraction procedure can be applied to genuine HLW solutions for effective reduction of the dose due to Cs so that HLW can be handled in fume hoods for its characterization.

Extraction generator of 223Ra for nuclear medicine

A novel 227Ac/223Ra extraction generator for nuclear medicine was developed. Its operation is based on selective extraction of 223Ra with a solution of chlorinated cobalt dicarbollide and polyethylene glycol in a polar diluent from a solution of a mineral acid and a complexing agent. Radium is stripped to any appropriate aqueous solution on adding TBP into the extractant. Trials performed in the manual mode showed that 223Ra is efficiently separated from the parent isotopes 227Ac and 227Th (decontamination factor of 223Ra from 227Ac and 227Th >106). It is the most convenient to use the 223Ra generator for the radionuclide production in a regional center, because it allows fairly simple production of large batches of 223Ra, avoiding problems associated with the need for skilled staff for working with the generator in a medical center and with the radiation-induced degradation of the matrix (ion-exchange resin).

Thermodynamics of Cesium Extraction from Acidic Media by HCCD and PEG

In this study, details of cesium extraction from nitrate media using chlorinated cobalt dicarbollide (HCCD) dissolved in the polar phenyl trifluoromethyl sulfone (FS-13) diluent have been examined. It has been verified that Cs+ phase transfer is based solely on cation exchange (H+ for Cs+) that is, that a previously reported nitrate dependency arises from nonideal behavior of solute species. The enthalpy and entropy of the system calculated using appropriate corrections to the van't Hoff analysis are found to be in good agreement with independently measured calorimetry results. Finally, it is demonstrated that synergistic extraction of Cs+ by HCCD and PEG does not occur. Although there is a definite interaction between HCCD and PEG (and it is well established that this interaction is responsible for the extraction of Sr2+), this association is actually antagonistic to the extraction of Cs+.

Selective separation of radio-cesium from acidic solutions using supported liquid membrane containing chlorinated cobalt dicarbollide (CCD) in phenyltrifluoromethyl sulphone (PTMS)

A supported liquid membrane method was developed using chlorinated cobalt dicarbollide (CCD) in phenyltrifluoromethyl sulphone (PTMS) as the carrier, impregnated in PTFE flat sheet membranes for the selective separation of Cs(I) from nitric acid feed solution. Solvent extraction studies were carried out for optimizing the feed as well as strip conditions. >95% Facilitated transport of Cs(I) was observed in about 3 h when 1 M HNO 3 and 8 M HNO 3 were used as the feed and strip solutions, respectively while 0.025 M CCD in PTMS was used as the carrier extractant. Selectivity studies, carried out using a mixture of radiotracers viz. 51Cr, 59Fe, 99Mo, 99mTc, 106Ru, 137Cs, 152Eu and 241Am, indicated selective transport of Cs(I) with DF values >100. Though reproducibility of the transport data was excellent when carried out in two successive transport experiments with freshly loaded carrier solvent, the stability of the membrane was poor which restricts its long term use.