Evaluation of Novel Solvent Systems Containing Calix-crown-6 Ligands in A Fluorinated Solvent for Cesium Extraction from Nitric Acidic Feeds

Several commercial calix-crown-6 ligands such as: calix[4]arene-bis-crown-6 (CC), calix[4]arene-bis-benzo-crown-6 (CBC), calix[4]arene-bis-naphtho-crown-6 (CNC), and bis-(octyloxy)calix[4]arene-mono-crown-6 (CMC) have been evaluated for their Cs uptake ability from nitric acid feed solutions in a novel solvent system. The calix-crown-6 ligands were made soluble in phenyl trifluoromethyl sulphone (PTMS) and 1 × 10^?3 M solutions were used for metal ion extraction from nitric acid feed solutions. The extraction efficiency of the calix-crown-6 ligands was found out to be: CBC > CNC > CMC ? CC, which was attributed to trends of their partition coefficients. CNC was considered to be the most suitable extractant in view of its better organophilicity. The effects of concentrations of nitric acid and Cs carrier in feed were also investigated. Studies carried out using variation of ligand concentration yielded an extracted species of the type [CsL⁺][NO₃^?]_org. Stripping of Cs(I) from the loaded organic phase was found to be possible when the organic phase contained minute quantities of Alamine 336. Co-current extraction and stripping studies were also carried out using CNC as the extractant.     

Hydraulic and Mass-Transfer Performance of a 20-Mm-Diameter Annular Centrifugal Contactor for the Solvent Extraction of Cesium by Bis(2-Propyloxy)Calix[4]-Crown-6 in n-Octanol

A calixcrown extraction process using bis(2-propyloxy)calix[4]-crown-6 (iPr-C[4]C-6) as extractant and n-octanol as diluent for the separation of cesium from Chinese High Level Liquid Waste (HLLW) has been developed at INET. Chinese HLLW is acidic defense waste with high salt content, which is now stored in underground stainless steel tanks. The intention is to use a process to extract cesium from HLLW conducted on multistage 20-mm-diameter annular centrifugal contactors (ACCs), so it is necessary to study the hydraulic and mass-transfer performance of a 20-mm-diameter ACC for the extraction system. In this work, the effects of the parameters such as the rotor speed, the diameter of heavy weir, and the acid concentration on the hydraulic performance were investigated. An operational envelope of the 20-mm-diameter ACC for the n-octanol/aqueous solution system was identified. The mass-transfer efficiency of the single stage 20-mm-diameter ACC for the extraction and stripping of cesium with iPr-C[4]C-6 in n-octanol was studied by varying several parameters, such as the rotor speed, the total flow rate, and the flow ratio. The extraction stage efficiency is greater than 95% at suitable operating conditions for extracting Cs⁺ with 0.025 mol/L of iPr-C[4]C-6 in n-octanol from HNO₃ solution containing Cs⁺. The stripping stage efficiency of Cs⁺ (< 90%) is lower than the extraction stage efficiency of Cs⁺.     

Optimization Studies for the Recovery of Thorium from Advanced Heavy Water Reactor High Level Waste (AHWR-HLW) Solutions Using Green Solvents

An Advanced Heavy Water Reactor (AHWR) has been specifically designed to exploit Th/²³³U as fuels. The reprocessing is focused mainly on the recovery of ²³³U and Pu from the spent fuels leaving bulk of Th (～100 g/L) in the High Level Waste (HLW) solutions. No systematic attempts have been made so far to identify suitable solvents for the recovery of thorium from high level waste (HLW) solutions generated after AHWR spent fuel reprocessing. Tri-n-butyl phosphate (TBP), though the work horse for nuclear fuel reprocessing as an extractant, suffers from the serious limitation of third-phase formation during the extraction of macro concentrations of thorium. Two straight chain dialkyl amides such as N,N-dihexyl octanamide (DHOA), and N,N-dihexyl decanamide (DHDA) as well as TBP were evaluated for the recovery of the thorium from AHWR-HLW solutions. Attempts were made to identify suitable solvent (extractant + diluent) system and optimize the conditions for the recovery of thorium from HLW solutions. Selectivity of the solvents was examined for thorium extraction over fission products/structural materials under AHWR raffinate solutions. Counter-current centrifugal contactor runs were also carried out on simulated waste solutions to validate the optimized conditions for the recovery of thorium from the simulated AHWR waste solutions.     

Extracting Performance of Cesium by 25,27‐Bis(2‐Propyloxy) Calix[4]‐26,28‐Crown‐6 (iPr‐C[4]C‐6) in n‐octanol

Abstract

In this work, the extraction of cesium(Cs⁺) in nitric acid and in a simulated high level liquid waste (HLLW) by iPr‐C[4]C‐6 was investigated in the diluent n‐octanol. The slope of the extractant dependency equals 1, indicating that the complex has 1∶1[Cs⁺ · iPr‐C[4]C‐6]Cs⁺ to ligand. 0.025 mol/L iPr‐C[4]C‐6 in n‐octanol (abbreviated to iPr‐C[4]C‐6‐n‐octanol) has a stronger extracting ability to Cs when acidities are between 1.0 mol/L and 4.0 mol/L. The stripping properties of Cs loading in 0.025 mol/L iPr‐C[4]C‐6‐n‐octanol was studied. Cs loading in iPr‐C[4]C‐6‐n‐octanol can be stripped easily into the aqueous phase because the distribution ratios of Cs are lower than 0.5 when pH is between 2 and 10 in the aqueous phase. On the above basis, the better parameters were selected and the cold cascade test for removing Cs from the simulated HLLW was investigated on miniature centrifugal contactor. The results of the test are attractive. The removing ratio of Cs from the simulated HLLW is 99.5% and the stripping ratio of Cs loading in 0.025 mol/L iPr‐C[4]C‐6‐n‐octanol is 99.2%. The results show that 0.025 mol/L iPr‐C[4]C‐6‐n‐octanol is an effective process for removing Cs from HLLW.     

Selective transport of radio-cesium by supported liquid membranes containing calix[4]crown-6 ligands as the mobile carrier

Facilitated transport of Cs-137 across supported liquid membranes (SLM) containing a calix-crown ligand viz. caliz[4]arene-bis(crown-6) (CC), calix[4]arene-bis(o-benzocrown-6) (CBC) or calix[4]arene-bis(napthocrown-6) (CNC) was investigated. The feed consisted of dilute nitric acid solutions while the carrier solutions contained mainly CNC in several organic diluents inside the pores of polypropylene (PP) as well as PTFE flat sheet membranes. PTFE membranes containing CNC in a diluent mixture of 2-nitrophenyloctyl ether (NPOE) and n-dodecane were found to have high stability. Selectivity studies were carried out using simulated high level waste (SHLW) as well as fission products obtained from an irradiated natural uranium target.     

Solvent Extraction and Separation of Gallium(III) using Hexaacetato Calix(6)Arene

Gallium(III) was extracted at pH 3.5 by equilibrating eight min with 10 mL of 0.0001 M acetyl derivative of calix(6)arene in xylene. Gallium(III) was stripped quantitatively with 0.1 N hydrochloric acid and determined spectrophotometrically with 0.01% PAR at 510 nm. The nature of the extracted species was determined from the log-log plots and its stoichiometry was confirmed by numerical treatment to experimental data. The IR analysis of Ga(III) loaded organic phase was also studied. The conformational change of reagent during complex formation was studied from the ¹H NMR treatment. The temperature dependence of the extraction equilibrium and metal loading capacity of the reagent was also evaluated. The proposed method was successfully applied for the extraction and separation of multicomponent mixtures, synthetic mixtures, and binary and ternary separation of gallium from the associated elements. The results obtained were reproducible and accurate.     

Synthesis of a Novel Macroporous Silica-Calix[4]arene-Crown Supramolecular Recognition Material and its Adsorption for Cesium and some Typical Metals in Highly Active Liquid Waste

Abstract

A novel macroporous silica-based 25,27-bis(iso-propyloxy)calix[4]arene-26,28-crown-6 (BiPCalix[4]C6) supramolecular recognition material, BiPCalix[4]C6/SiO₂-P, was synthesized. It was prepared by impregnation and the immobilization of the BiPCalix[4]C6 molecule into the pores of the macroporous SiO₂-P particles. The adsorption of Cs(I) and some typical elements Na(I), K(I), Rb(I), Sr(II), Ba(II), Ru(III), Mo(VI), La(III), and Y(III) onto the BiPCalix[4]C6/SiO₂-P material was investigated. The effects of the HNO₃ concentration, contact time, and temperature on the adsorption of the tested metals were studied. It was found that at the optimum concentration of 3.0 M HNO₃, BiPCalix[4]C6/SiO₂-P exhibited excellent adsorption ability and high selectivity for Cs(I) over all the tested elements, which showed weak or almost no adsorption except Rb(I). A pseudo-second-order model was found to be able to describe the adsorption kinetics of Cs(I). The chemical complexation of Cs(I) with BiPCalix[4]C6/SiO₂-P was considered to be the rate-controlling step. Meanwhile, the thermodynamic parameters of the Cs(I) adsorption, ΔH?, ΔG?, and ΔS? were determined. The adsorption of Cs(I) onto BiPCalix[4]C6/SiO₂-P was exothermic. It was demonstrated that in 3.0 M HNO₃, the novel macroporous BiPCalix[4]C6/SiO₂-P material shows promise for the partitioning of Cs(I) from highly active liquid waste.     

Solvent Extraction of U(VI) by Calix[6]arenes

Abstract

This paper focuses on the solvent extraction of U(VI) traces by 1,3,5‐OMe‐2,4,6‐OCH₂CONHOH‐p‐tert‐butylcalix[6]arene (LH₃). The global extraction equation of U(VI) has been established. The complex formed in the organic phase is (UO₂)(LH) with an apparent extraction constant equal to 7.1×10^?5 M (I=0.04 M). Distribution data show that LH₃ efficiently extracts U(VI) from NaNO₃ media at pH 5 and that the stripping of U(VI) can be achieved in nitric acid solutions. Finally a comparison with previous results obtained with the 1,3,5‐OMe‐2,4,6‐OCH₂COOH‐p‐tert‐butylcalix[6]arene (L′H₃) shows that the hydroxamate groups are as efficient as the carboxylate ones for uranyl extraction.     

Efficient co-extraction of strontium and cesium from nitric acid medium by mixtures of di-tert-butylcyclohexano-18-crown-6 and 1,3-di(2-propoxy)calix[4]arene-crown-6 in n-octanol

The co-extraction of strontium and cesium from nitric acid medium by di-tert-butylcyclohexano-18-crown-6 (DtBuCH18C6) and 1,3-di(2-propoxy)calix[4]arene-crown-6 (iPr-C[4]C-6) in n-octanol was studied. The effects of contact time, nitric acid concentration, extractant concentration and temperature on the co-extraction behavior were systematically investigated. Effective extraction of the two metals was achieved under a variety of conditions. The co-extraction from a simulated high-level liquid waste (HLLW) was also conducted, and strontium and cesium could be selectively extracted in the presence of a large number of other metals. Results in this work illustrate the feasibility of partitioning radioactive strontium and cesium simultaneously from HLLW by a mixture of DtBuCH18C6 and iPr-C[4]C-6 in n-octanol.     

Synthesis of Various Calix[4]arene Derivatives with Mercaptoalkyl Chains and Their Application in Removing Cr(VI) from Aqueous Solution

Four different mercaptoalkyl-substituted calixarene derivatives (5,11,17,23-tetra-tert-butyl-25,27-bis(3-mercaptopropoxyl)-26,28-dihydroxycalix[4]arene, 25,27-bis(3-mercaptopropoxyl)-26,28-dihydroxycalix[4]arene, 25,27-bis(5-mercaptopentanoxyl)-26,28-dihydroxycalix[4]arene and 5,17-di-tert-butyl-11,23-di-carboxyl-26,28-bis(3-mercaptopropoxyl)-25,27-di-hydroxycalix[4]arene) were synthesized. Their structures were characterized by Fourier transform infrared spectroscopy (FTIR), ¹H and ¹³C NMR spectroscopy, and elemental analysis techniques. Moreover, their extraction capabilities at different parameters such as pH, shaking speed, and shaking time were examined toward dichromate ions. Results implied that all mercaptoalkyl-substituted calixarene derivatives showed an extraction capability toward dichromate anion while the carboxyl-functionalized calixarene-marcapto-alkyl derivative exhibited the highest extraction capability.     

Highly Lipophilic,Mono-ionizable Calix[4]arene-benzocrown-6 Extractants for Removal of Radiocesium from Nuclear Wastes

A series of lipophilic, proton-ionizable calix[4]arene-benzocrown-6 compounds with calixarene units locked in the 1,3-alternate conformation was prepared for evaluation of their potential as radiocesium ion extractants. Upon ionization of the pendant acidic function, the ligand provides the requisite anion for the formation of an electroneutral extraction complex, thereby markedly increasing Cs⁺ extraction efficiency. To enhance the lipophilicity, each proton-ionizable calix[4]arene-crown-6 ligand bears a (2-ethylhexyl)benzo unit and two octyl groups. By use of radiotracer techniques for Cs⁺ and Na⁺ and ICP spectrometry for K⁺, the ligands were evaluated in terms of the efficiency and selectivity with which they extract Cs⁺ from aqueous solutions into toluene. Supplementary materials are available for this article. Go to the publisher's online edition of Solvent Extraction and Ion Exchange to view the supplementary file.     

Flotation of Cesium Coprecipitated with Nickel Hexacyanoferrate(II) from Aqueous Solutions and Radioactive Waste Simulants

Abstract

The coprecipitate flotation of ¹³⁷Cs from dilute aqueous solutions and simulated radioactive wastes using nickel hexacyanoferrate(II) as a coprecipitant and sodium lauryl sulfate, cetyltrimethylammonium bromide, or dodecyl amine as a collector was extensively investigated to establish the best conditions for cesium removal. Under the optimal conditions, removals exceeding 99% and decontamination factors higher than 110 could be achieved for the radioactive waste simulants. The results are compared with those obtained by conventional removal methods and are discussed in terms of the collector properties and the electrical state of the coprecipitate.     

Solvent Extraction Studies for Separation of Zn(II) and Mn(II) from Spent Batteries Leach Solutions

This study aims at assessing the possibility of using solvent extraction processes for separating Zn(II) and Mn(II) dissolved in aqueous solutions obtained by acid bioleaching of spent alkaline and Zn-C batteries. In this context, Cyanex 272 and DEHPA were tested as extractant agents, and the former was shown to have better performance. Hence, the effect of four factors (equilibrium pH, extractant concentration, A/O ratio, and temperature) into three response variables (extraction efficiency of Zn, Y_Zn; extraction efficiency of Mn, Y_Mn; separation factor, β) were tested according to a full factorial design (2⁴) with two replicated center points. Our study revealed that Y_Zn depends mainly on the extractant concentration, Y_Mn on the equilibrium pH and β on the equilibrium pH, extractant concentration, and A/O ratio as well as on second and third order interactions. One extraction step is sufficient to reach high extraction of zinc in synthetic solutions, but two stages were required for real leaching liquor. The extraction kinetics is fast (less than 15 min) for both metals, even when real liquor was tested. The organic solvent can be efficiently recovered using a stripping solution of H₂SO₄ 1 M and thus the process can be considered environmentally sustainable.     

Adsorption Behavior of Platinum Group Metals onto a Silica-based (Crea+Dodec)/SiO2-P Extraction Resin from Simulated High Level Liquid Waste

Basic properties of a silica-based macroporous N’,N’-di-n-hexyl-thiodiglycolamide (Crea) extraction resin, (Crea+Dodec)/SiO₂-P were examined. This extraction resin was synthesized by impregnating Crea and its modifier, n-Dodecyl alcohol (Dodec) into the macroporous SiO₂-P support with a mean diameter of 50 μm. Adsorption behavior of platinum group metals (PGMs) and some fission product elements from simulated high level liquid waste onto the resin was investigated by batch experiment. It was found that (Crea+Dodec)/SiO₂-P extraction resin exhibited good adsorption selectivity for PGMs over other tested elements in 0.1-5.0 M HNO₃ solution. This resin showed strong affinity to Pd(II) especially in a short contact time but almost no adsorption for rare earth elements. Adsorption behavior of PGMs in experiment could be expressed by the Langmuir monomolecular layer adsorption mode. Meanwhile, adsorption results were fitted well with the pseudo-second order model and the rate-controlling step of this adsorption process was governed by the chemisorption process. In addition, the adsorption isotherms and thermodynamic parameters of tested elements were calculated by the Langmuir, Freundlich, and van’t Hoff equations, respectively.     

Comparative Evaluation of CMPO and Diglycolamide Based Solvent Systems for Actinide Partitioning in Mixer-Settler Runs Using Tracer-Spiked PHWR Simulated High Level Waste

The TRUEX solvent (0.2 M CMPO + 1.2 M TBP) was employed for countercurrent extraction studies with radiotracers spiked pressurized heavy water reactor simulated high level waste (PHWR-SHLW) employing a 12-stage of mixer-settler. The results of the mixer-settler runs with CMPO were compared with those obtained under identical conditions employing TODGA (N,N,N’,N’-tetraoctyl diglycolamide) and T2EHDGA (N,N,N’,N’-tetra-2-ethylhexyl diglycolamide) as the extractants. Even though the TRUEX solvent revealed quantitative extraction of trivalent actinides and lanthanides in 5 stages at O/A = 1, stripping of the extracted metal ions from the loaded organic phase was poor with dilute HNO₃ solution (0.2 M HNO₃). Quantitative stripping could not be achieved in 12 stages even when a complexing solution (0.1 M citric acid + 0.1 M HNO₃) was employed as the strippant. In contrast, the stripping from loaded TODGA and T2EHDGA solvents was possible in < 6 stages with 0.2 M HNO₃. The experimental results suggested that the performance of TRUEX solvent was inferior to the diglycolamide based extractants such as TODGA and T2EHDGA.     

Removal and Separation of Some Radionuclides by Poly-acrylamide Based Ce(IV) Phosphate from Radioactive Waste Solutions

Removal of cesium, cobalt, and europium ions from radioactive waste solutions using poly-acrylamide based Ce(IV) phosphate material was investigated using both batch and fixed bed column techniques. The effect of pH, initial metal ion concentration, and temperature had been studied. Simple kinetic and thermodynamic models had been applied from which the mechanism of the process and the thermodynamic parameters were determined. The positive values of enthalpy change, ΔH, obtained for the three metal ions confirmed the endothermic nature of the sorption process and suggested that chemisorption is the predominant sorption mechanism. The high positive values found for the entropy change, ΔS, show the increased randomness at the solid/solution interface. The obtained negative values of free energy change, ΔG, indicating the feasibility and the spontaneous nature of the sorption processes. Breakthrough data were investigated in a fixed bed column at room temperature (298 K) under the effect of various process parameters like bed depth, flow rate, and initial ion concentration. The results showed that the overall bed capacity decreased with increasing flow rate and increased with increasing initial metal ion concentrations and bed depth.     

Extraction of Lanthanides(III) from HClO4 Solutions with Bis(diphenylphosphorylmethylcarbamoyl)alkanes

Abstract

Novel polyfunctional neutral organophosphorus compounds, namely bis(diphenylphosphoryl-methylcarbamoyl)alkanes of general formula [Ph₂P(O)CH₂C(O)NH]₂(CH₂)_n (I-III; n = 3, 5, 8), were synthesized and studied as extractants for La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y from perchloric acid solutions. The influence of both of HClO₄ concentration in the aqueous phase and that of the extractant in the organic phase on the extraction of metal ions is considered. The stoichiometry of the extracted complexes has been determined. Bis(diphenylphosphorylmethylcarbamoyl)alkanes II and III possess a higher extraction efficiency towards Ln(III) than their monoanalogue Ph₂P(O)CH₂C(O)NHC₉H₁₉. The potentialities of polymeric resin impregnated with bis(diphenylphosphorylmethylcarbamoyl)pentane II for the preconcentration of lanthanides(III) from perchloric acid solutions are demonstrated.     

The Screening of Extractants for the Separation of Zn(II) from Australian Hot-Dip Galvanizing Effluent

In this study, the most appropriate organic phase for the selective extraction of Zn(II) from Australian hot-dip galvanizing effluent streams has been determined. TBP (tributyl phosphate) and Hostarex A226 (diisotridecylamine) were identified as the most favourable for the extraction of zinc ions from a chloride matrix. Two alternatives, Hostarex A324 (tri-iso-octlyamine) and Hostarex A327 (tri-n-octyl/n-decylamine), were also tested. Laboratory scale shake tests were conducted using model solutions containing a range of acid concentrations and zinc concentrations up to 80 g/L. Industrial pickling effluent was used to test the effect of impurities present. The use of TBP was confirmed as the most appropriate extractant.     

对叔丁基杯[4]及杯[6]芳烃的合成及其对铜离子的萃取研究

以对叔丁基苯酚和甲醛为原料,分别对对叔丁基杯[4]及杯[6]芳烃的合成和萃取性质进行了研究．结果表明,在本研究范围内,以KOH为催化剂,对叔丁基杯[6]芳烃的最高产率为77．8％;以NaOH为催化剂,对叔丁基杯[4]芳烃的最高产率为47．3％。对于对叔丁基杯[4]和杯[6]芳烃,最佳的反应回流温度都为140℃。对叔丁基杯[6]芳烃对模拟废水中的铜离子具有一定的萃取效果,最高萃取率为70．3％。     

电镀重金属废水治理技术的发展现状(Ⅰ)

介绍了我国治理电镀废水的发展历程，较系统地评述了电镀重金属废水的各种治理技术——化学法、吸附法、高于交换法、电解法、膜分离法等的应用现状与发展趋势及其近年来在电镀废水治理技术的组合应用和多元综合防治技术的兴起与应用趋势。