Di-tert-butylcyclohexano-18-crown-6 Research Articles

Preparation of a Novel Silica-Based DtBuCH18C6 Impregnated Polymeric Composite Modified by Tri-n-butyl Phosphate and Its Application in Chromatographic Partitioning of Strontium from High Level Liquid Waste

To reduce significantly the leakage of 4,4',(5')-di-(tert-butylcyclohexano)-18-crown-6 (DtBuCH18C6), an improved silica-based polymeric composite, (DtBuCH18C6+TBP)/Si02-P, was prepared. It was done by impregnating and immobilizing DtBuCH18C6 and tri-n-butyl phosphate (TBP) molecules into the pores of SiO 2 -P particles through an advanced vacuum sucking technique. The adsorption of 10 typically simulated elements, Ru(III), Pd(II), Ba(II), Mo(VI), La(III), Y(III), Na(I), K(I), Sr(II), and Cs(I), toward (DtBuCH18C6+TBP)/Si02-P was investigated in the HNO 3 concentration range of 0.1-5.0 M. In optimum 2.0 M HNO 3 solution, (DtBuCH18C6+TBP)/Si02-P showed strong adsorption ability and high selectivity for Sr(II) over all of the tested elements. The quantity of total organic carbon (TOC), 281.8 ppm, leaked from (DtBuCH18C6+TBP)/Si02-P was much lower than that of 532.3 ppm leaked from DtBuCH18C6/SiO 2 -P. A significant reduction of DtBuCH18C6 leakage was achieved. In terms of the batch experiments, the chromatographic separation of Sr(II) from a 2.0 M HNO 3 solution was performed by a (DtBuCH18C6+TBP)/ SiO 2 -P packed column. Na(I), K(I), Cs(I), Pd(II), Mo(VI), La(III), Ru(III), and Y(III) were found to elute facilely and flow into the effluent along with 2.0 M HNO 3 because of the weak or no adsorption. Sr(II) and Ba(II) adsorbed strongly and were desorbed sufficiently by distilled water and then separated completely from the others. The recovery percentage was 100.5% for Sr(II) and in the range 99.2-100.6% for the others. The application of the macroporous silica-based (DtBuCH18C6+TBP)/Si02-P polymeric composite in partitioning of Sr(II) from high level liquid waste (HLLW) is promising.

Molecular modification of a novel macroporous silica-based impregnated polymeric composite by tri- n-butyl phosphate and its application in the adsorption for some metals contained in a typical simulated HLLW

Using tri- n-butyl phosphate (TBP) as a molecular modifier, a novel macroporous silica-based 4,4′,(5′)-di-( tert-butylcyclohexano)-18-crown-6 (DtBuCH18C6) polymeric composite (DtBuCH18C6 + TBP/SiO 2–P) was synthesized. It was done by impregnating and immobilizing DtBuCH18C6 and TBP molecules into the pores of SiO 2–P particles utilizing an advanced vacuum sucking technique. The adsorption of 10 fission and non-fission products Sr(II), Ba(II), Ru(III), Mo(VI), Na(I), K(I), Pd(II), La(III), Cs(I), and Y(III) onto (DtBuCH18C6 + TBP)/SiO 2–P was investigated by examining the influence of contact time and the HNO 3 concentration in a range of 0.1–5.0 M at 298 K. It was found that at the optimum concentration of 2.0 M HNO 3 (DtBuCH18C6 + TBP)/SiO 2–P exhibited strong adsorption ability and high selectivity for Sr(II) over all of the tested elements, which showed very weak or almost no adsorption except Ba(II). Moreover, the quantity of DtBuCH18C6 leaked from (DtBuCH18C6 + TBP)/SiO 2–P in 2.0 M HNO 3, 326.2 ppm, was obviously lower than 658.4 ppm that leaked from DtBuCH18C6/SiO 2–P. This was ascribed to the effective association of DtBuCH18C6 and TBP through intermolecular interaction, i.e., hydrogen bonding. The significant reduction of DtBuCH18C6 leakage by molecular modification with TBP was achieved. It was of great benefit to application of the (DtBuCH18C6 + TBP)/SiO 2–P polymeric composite in chromatographic partitioning of Sr(II), one of the main heat generators, from high level liquid waste (HLLW) in reprocessing of nuclear spent fuel in MAREC process developed recently.

Diluent effect on Sr(II) extraction using di- tert-butyl cyclohexano 18 crown 6 as the extractant and its correlation with transport data obtained from supported liquid membrane studies

The effect of organic diluents on the extraction of Sr(II) from an aqueous nitrate medium (containing a mixture of 2.0 M Al(NO 3) 3 + 0.5 M HNO 3) using di- tert-butylcyclohexano 18 crown 6 (DTBCH18C6) as the extractant was investigated. The diluent effect on the Sr(II) transport rates across supported liquid membranes (SLM) containing DTBCH18C6/diluent as the carrier was also investigated. Though diluents containing DTBCH18C6 alone have shown moderate transport rates, their 1:1 mixture with 1-octanol has shown significant enhancement in transport rates: a 1:1 chloroform–octanol mixture resulted in the highest distribution ratio values though the transport rates were at maximum with a tert-butyl benzene–octanol mixture. The extractability of the metal ion was correlated with Schmidt’s diluent parameter.

Bleeding evaluation of the stationary phase from a few novel macroporous silica-substrate polymeric materials used for radionuclide partitioning from HLLW in MAREC process

To separate minor actinides from HLLW by extraction chromatography, a few novel silica-based di(2-ethylhexyl)phosphoric acid (HDEHP), 4,4�,(5�)-di(tert-butylcyclohexano)-18-crown-6 (DtBuCH18C6), octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO), and N,N,N�,N�-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) polymeric adsorption materials (HDEHP/SiO2-P, DtBuCH18C6/SiO2-P, CMPO/SiO2P, and TODGA/SiO2-P) were synthesized by impregnating HDEHP, DtBuCH18C6, CMPO, and TODGA into the pores of porous SiO2-P particles, which were the new kind of inorganic/organic composites consisted of macroporous SiO2 and copolymer. The bleeding behavior of these composites was investigated by examining the effect of contact time and HNO3 concentration. It was found that in the tested HNO3 concentration range, a noticeable quantity of DtBuCH18C6, at least 600 ppm, leaked out from DtBuCH18C6/SiO2-P because of the protonation of DtBuCH18C6 with hydrogen ion, while the others were lower and basically equivalent to the solubility of HDEHP, CMPO, or TODGA in corresponding acidities solutions. Based on the batch experiment, the bleeding of CMPO/SiO2-P and TODGA/SiO2-P, the main adsorbents used in MAREC process for HLLW partitioning, was evaluated by column operation in 0.01M HNO3 and 3M HNO3. The quantity of CMPO leaked was �48 ppm in 0.01M HNO3 and �37 ppm in 3.0M HNO3. The bleeding of TODGA decreased from 23.2 ppm to 7.27 ppm at the initial stage and then basically kept constant. An actual bleeding of TODGA was evaluated by the separation of Sr(II) from a 2.0M HNO3 solution containing 5.0 . 10 –3 M of 6 typically simulated elements.

Synthesis of a novel macroporous silica-based polymeric material containing 4,4 ′,(5 ′)-di( tert-butylcyclohexano)-18-crown-6 functional group and its adsorption mechanism for strontium

A novel, specific macroporous silica-based 4,4 ′,(5 ′)-di( tert-butylcyclohexano)-18-crown-6 (DtBuCH18C6) chelating polymeric material (DtBuCH18C6/Si-polymer) was synthesized by impregnating DtBuCH18C6 molecule into the Si-polymer particles that was prepared by a series of polymerization reactions between ∼50 μm SiO 2 and a mixture of m/ p-divinylbenzene, α,α-azobisisobutyronitrile, 1,1-azobiscyclohexane-1-carbonitrile, m/ p-formylstyrene, methyl benzoate and diotylphthatate at 90 °C. This hydrophilic material exhibited the much higher adsorption ability for Sr(II) than that of a commercial Sr-resin, an inert conventional polymer-based adsorbent. The complex composition between DtBuCH18C6/Si-polymer and Sr(II) was determined as 1:1 type by investigating the influence of the concentrations of DtBuCH18C6, Sr(II), H + and NO 3 − on the adsorption of Sr(II) onto DtBuCH18C6/Si-polymer. The adsorption equilibrium equation was described as follows Sr 2+ ( aq) + 2 NO 3( aq) −+ DtBuCH18C6/Si-polymer ( re) ↔ Sr( NO 3) 2· DtBuCH18C6/Si-polymer ( re) The apparent adsorption equilibrium constant was calculated to be log K ad=2.21±0.15 at 2.0 M HNO 3 at 25 °C. The monolayer molecule adsorption mechanism was determined by examining the relationships between −ln(1− F) and t and lnt, respectively. The corresponding adsorption equations at different temperatures were obtained. The chelating effect of the DtBuCH18C6/Si-polymer adsorbent for Sr(II) was considered as the mainly adsorptive pathway.

Novel polymer inclusion membrane containing a macrocyclic ionophore for selective removal of strontium from nuclear waste solution

A new polymer inclusion membrane (PIM) containing cellulose triacetate (CTA) as the monomer, di-tert-butylcyclohexano-18-crown-6 (DtBuCH18C6) as the carrier and 2-nitrophenyl octyl ether (NPOE) as the plasticizer was developed for the selective transport of Sr2+ from aqueous nitrate medium. Studies with crown ether concentration variation have indicated a linear dependence on the permeability coefficient (P) suggesting a diffusion mechanism for ion transport. Effects of membrane thickness, nature of plasticizer and plasticizer concentration on the transport of Sr2+ were studied. The effect of feed acidity was also investigated for a possible application in the nuclear waste solution. Selective Sr2+ transport was observed in a synthetic waste solution containing metal ions such as UO22+, MoO22+, Zr4+, Ce3+, Nd3+, Ru3+, Pd2+, Ba2+ and Cs+, etc., in 1 M HNO3 and 2 M NaNO3. Greater than 70% transport of Sr2+ was observed in 24 h while most of the other metal ions were negligibly transported (<0.01%).

Kinetics of the adsorption of strontium(II) by a novel silica-based 4,4',(5')-di(tert-butylcyclohexano)-18-crown-6 extraction resin in nitric acid medium

A new type of silica-based chelating extraction resin, DtBuCH18C6/SiO2-P, was prepared by impregnating a crown ether derivative, 4,4¢,(5¢)-di(tert-butylcyclohexano)-18-crown-6 (DtBuCH18C6), into the porous silica/polymer composite particles (SiO2-P). The adsorption of Sr(II) and some other fission product elements was investigated by a batch adsorption experiment in HNO3

Comparison of Column Chromatographic and Precipitation Methods for the Purification of a Macrocyclic Polyether Extractant

Column chromatography on aminopropyl-derivatized silica and precipitation of a complex with perchloric acid have been evaluated as methods for the purification of di-tert-butylcyclohexano-18-crown-6 (DtBuCH18C6), a compound frequently employed for the selective extraction of strontium from acidic nitrate media. Both methods are shown to provide a simple and effective means of eliminating inactive sample components (i.e., impurities or stereoisomers incapable of extracting strontium) from the crown ether and enriching the material in 4(z),4′(z) cis-syn-cis DtBuCH18C6, a stereoisomer capable of highly efficient strontium extraction.

Influence of the Extractant on Strontium Transport from Reprocessing Concentrate Solutions through Flat-Sheet Supported Liquid Membranes

Abstract The influence of the extractant on strontium transport through a flat-sheetsupported liquid membrane from nuclear fuel reprocessing concentrate solutions to demineralized water has been studied using two crown ethers of different lipophilicity: dicyclohexano-18-crown-6 (DC18C6) and di-tert-butylcyclohexano-18-crown-6 (DtBuC18C6). The distribution coefficients of strontium showed that DC18C6 is a better strontium extractant than DtBuC18C6 in the entire range of crown-ether concentration studied. No effect of association between the DC18C6 molecules was observed even at high concentrations. However, the strong lipophilic character of DtBuC18C6 led to a distribution coefficient of this extractant 10 times higher than the distribution coefficient of DC18C6. Thus, the membrane concentration of DtBuC18C6 was approximately 10 times higher than that of DC18C6. This leads to greater strontium permeability for DtBuC18C6, even though DC18C6 had a greater capacity for strontium extraction and a higher diffusion coefficient in the membrane due to the smaller molar volume of this crown ether. The precipitation of a white solid was observed when the synthetic concentrate was mixed with an organic phase containing DtBuC18C6 dissolved in n-hexylbenzene (0.7 mol·L−1 isotridecanol), causing a decrease of strontium permeability. In this case, DC18C6 had the greatest strontium permeability.