•A new triazine-containing hybrid silica-material was prepared and characterized.•The material exhibited strong uptake ability and selectivity for Pd over others.•The removal of Pd was more than 99.3% in batch uptake and desorption cycles.•An efficient technical process entitled SPMP for Pd separation was developed.•A novel pathway for simultaneous separation of MA and Pd has been proposed.The efficient separation of palladium, one of the precious metals, is one of the most challenging works that have not been solved. Based on soft-ligand multi-nitrogen organic agents, a new triazine-containing hybrid functional silica-adsorbent, BisDiOTP@SiO2, was prepared and characterized. The uptake of more than ten representative metals towards BisDiOTP@SiO2 was investigated in the wide range of 0.4 –5.0 M HNO3. The high uptake ability and excellent selectivity of Pd(II) towards BisDiOTP@SiO2 were indicated. The enrichment and removal of Pd(II) by batch experiments through six cycles of uptake and desorption were conducted. The separation efficiency was 99.3% for Pd(II), 5.9% for Co(II) and less than 0.2% for all others. Pd(II) was separated effectively from others. A new technical process entitled SPMP (Simultaneous Partitioning of MA(III)/Pd(II) by Extraction Chromatography) for Pd(II) separation along with minor actinides has been developed.Download high-res image (140KB)Download full-size image

A polycrown loaded silica composite material named Polycrown/SiO2-P was firstly prepared by impregnating and immobilizing polycrown into porous silica and was characterized by scanning electron microscope (SEM), and Fourier transformed infrared (FT-IR) spectroscopy, nitrogen adsorption and desorption isotherms. Polycrown/SiO2-P was tested with regard to adsorption performance. Interestingly, Polycrown/SiO2-P preferred Pd(II) than alkali metals, alkaline-earth metals and actinides. Pd(II) adsorption with Polycrown/SiO2-P as functions of HNO3 concentration, contact time, initial Pd(II) concentration, temperature were thus investigated. The results showed the optimal adsorption acidity was determined as 5.0 M nitric acid, proving good acidity-resistant. Pseudo-second-order kinetics model fitted adsorption well indicating chemical adsorption. The isotherm adsorption equilibrium was well described by Langmuir isotherm model with maximum adsorption capacity of 14.30 mg/g. Pd(II) adsorption increased with temperature increased. The positive ΔH° and ΔS°, and the negative ΔG° indicated the adsorption was endothermic, entropy increase and spontaneous in nature. Pd(II) loaded Polycrown/SiO2-P was characterized by XPS. Further, the adsorption efficiency of recovered Polycrown/SiO2-P retained up ~93.7% after five ad-desorption cycles. Polycrown/SiO2-P was promising to separate Pd(II) from highly acid medium.

•A new asymmetric N-donor bipyridine-derivative was synthesized and crystallographic characterized.•A novel soft N-donor silica-bipyridine asymmetric adsorbent was prepared.•It was systematically characterized by SEM, XRD, 29Si NMR, EDS and XPS.•It showed fast adsorption kinetics, excellent adsorption ability and high selectivity toward Pd(II).The effective removal of heavy metal 107Pd(II) from highly active liquid waste (HLW) is very valuable for reducing its hazardous and risk to public health and environment. For this purpose, a novel silica-bipyridine multidentate functional adsorbent was synthesized by vacuum infusing a new asymmetric N-donor ligand CA-MTBP (bipyridine derivative) into the macroporous SiO2-P support. SEM, N2 adsorption–desorption isotherms, TGA, XRD, FT-IR, 29Si solid-state NMR and XPS spectroscopy were utilized to systematically characterize the physicochemical properties of the adsorbent. The characterization results indicated that CA-MTBP was successfully immobilized onto the pores of SiO2-P by intermolecular interaction. Strong hydrogen-bonding interactions identified by single crystal structure of the ligand and 29Si NMR may play a key role in achieving this immobilization. TGA and TOC studies showed that CA-MTBP/SiO2-P had excellent thermal stability and highly HNO3 resistance. EDS and XPS investigations provided directly evidences for Pd(II) being selectively adsorbed onto the adsorbent. The adsorbent had excellent adsorption capability, fast adsorption kinetics and high selectivity for Pd(II) over other typical tested metals in HNO3 media.Download high-res image (116KB)Download full-size image

•A novel silica-calix[4]biscrown hybrid material was prepared and characterized.•The materials exhibited strong adsorption ability and high selectivity for Cs(I).•The removal of Cs(I) was more than 99.1% in the batch adsorption and desorption cycles.•The individual separation of Cs(I) from HNO3 was achieved by extraction chromatography.•A new separation process entitled PCEC was proposed.To separate Cs(I), a new silica-calix[4]biscrown hybrid material, 1,3-calix[4]arene-bis(naph-crown-6) (CalixBNaphC)@SiO2-P, was synthesized by impregnation in situ and immobilization of agent into the pores of the SiO2-P particles. The materials were characterized by SEM images, FT-IR spectra, nitrogen adsorption-desorption isotherms and 29Si solid-state CP/MAS NMR. The adsorption of Cs(I) and some typical metals onto CalixBNaphC@SiO2-P was investigated by examining the effect of contact time and HNO3 concentration in the range of 0.4–6.0 M. Enrichment and recovery of Cs(I) in batch experiments were performed by six adsorption and desorption cycles. The removal of Cs(I) was more than 99.1%. Based on the batch results, the chromatographic separation of Cs(I) from 3.0 M HNO3 was conducted by CalixBNaphC@SiO2-P packed column. The effective separation of Cs(I) was achieved utilizing 3.0 M HNO3 and water as eluents. A new process entitled PCEC (Partitioning of Cesium by Extraction Chromatography) for individual separation of Cs(I) was developed.

Soft N-donor bis-triazine ligands developed for the separation of minor actinides (MAs) from lanthanides have been intensively studied for the past two decades. However, the investigation on the recovery and complexation of fission products Pd(II) with these ligands has rarely been reported to date. Herein, the synthesis, and solvent extraction of Pd(II) and some typical metals from HNO3 solutions as well as Pd(II) complexation with a new soft N-donor ligand C9-BTBP were presented. The C9-BTBP ligand exhibited high extraction capability and high selectivity for Pd(II) in HNO3 solution. Both 1:1 and 2:1 Pd(II)–C9-BTBP complexes were found in solution by a combination of ESI-MS and 1H NMR titration experiments. A solid binuclear Pd(II) complex [Pd2(NO3)4·(C9-BTBP)]·2.5H2O was synthesized and characterized by elemental analysis, DSC-TGA and 1H NMR. This is the first example that a binuclear Pd(II) complex with any N-donor bis-triazine ligand has been confirmed both in solution and in the solid state.

Comparative studies were performed toward adsorption kinetics and equilibrium of phenylethyl alcohol (PEA) onto three typical types (F400D, CAL, and 207CX) of granular activated carbons (GAC). The effective diffusion coefficients were of the order of 10–12 m2·s–1 for PEA adsorption on the GAC at 298 K. Desorption ratios of PEA from GAC were 92.2–99.9% achieved by methanol in batch mode at 298 K. Among the GAC employed, the carbon CAL proved to be superior in terms of physical properties as well as adsorption capacity and rate toward PEA. Dynamic adsorption was investigated using this optimal activated carbon. The maximum bed saturation capacity toward PEA was 2.471 mmol·g–1 under optimal conditions (GAC mass 10.01 g, inlet concentration 4.391 mmol·kg–1, flow rate 6.5 × 10–3 kg·min–1, temperature 298 K). The Yoon-Nelson model best described breakthrough data of PEA on GAC bed, whereas Yan and Clark models gave a relatively poor fit. The outcome of this work will facilitate adsorptive recovery of PEA from rose hydrolate byproduct using GAC.

•A novel hybridized macroporous silica-based supramolecular recognition material was prepared.•The functional materials exhibited strong adsorption ability and high selectivity for Sr(II) and Cs(I).•The simultaneous separation of both Cs(I) and Sr(II) from HNO3 was achieved by extraction chromatography.•A new separation process entitled GPSC was proposed.Based on the intermolecular modification of 1,3-[(2,4-diethylheptylethoxy)oxy]-2,4-crown-6-calix[4]arene (Calix[4]) with 4,4′,(5′)-di(t-butylcyclohexano)-18-crown-6 (DBC), a hybridized macroporous silica-based supramolecular recognition material, Calix[4]@DBC/SiO2-P, was prepared. The agents were impregnated and immobilized into the pores of the SiO2-P particles support. The adsorption of Cs(I), Sr(II), and some typical coexistent metals onto Calix[4]@DBC/SiO2-P was investigated. The influence of contact time and HNO3 concentration in the range of 0.4–6.0 M was studied. Calix[4]@DBC/SiO2-P exhibited high adsorption ability and selectivity for Sr(II) and Cs(I) except for Rb(I) and Ba(II). The simultaneous partitioning of Cs(I) and Sr(II) from a simulated highly active liquid waste was performed by Calix[4]@DBC/SiO2-P packed column. They were effectively eluted with water and flowed into effluent along with Rb(I) and Ba(II), while others showed no adverse impact. A new separation process, GPSC (Group Partitioning of Strontium and Cesium by Extraction Chromatography), for the separation of Cs(I) and Sr(II) was proposed.Graphical abstract

A new macrocyclic calix[4]arene-bis[(4-methyl-1,2-phenylene)-crown-6] (CalixBisMePhC) was synthesized. An extraction study of Cs(I), Na(I), K(I), Rb(I), Sr(II), Ba(II), Pd(II), and Ru(III) with CalixBisMePhC/CHCl3 was investigated by examining the effects of contact time, HNO3 concentration, and temperature. The results showed that due to the effective molecular recognition, CalixBisMePhC/CHCl3 had excellent extraction ability and high selectivity for Cs(I) over the tested metals except Rb(I). The maximum distribution ratio for Cs(I) was found at the HNO3 concentration of 4.4 mol·kg–1. The composition of the extracted species of Cs(I) was determined to be CsNO3·0.5CalixBisMePhC·0.5HNO3 by a slope method. Some valuable parameters for the Cs(I) extraction were obtained. The results demonstrated that the CalixBisMePhC/CHCl3 extraction system is promising to partition Cs(I) from highly level liquid waste.

A macrocyclic supramolecular recognition agent, 1,3-bis(1-nonyloxy)-2,4-crown-6-calix[4]arene (NonCalix[4]C6), was synthesized. The extraction of Cs(I), a heat generator, and some typical fission and nonfission products, La(III), Y(III), Rb(I), Mo(VI), Zr(IV), Sr(II), Ba(II), Ru(III), Na(I), K(I), and Pd(II), with NonCalix[4]C6/1-octanol in HNO3 medium was investigated. The effects of contact time, the concentration of HNO3 in the range of (0.4 to 5.0) mol·kg–1, and temperature were evaluated. NonCalix[4]C6 showed excellent extraction ability and high selectivity for Cs(I) over the tested metals except Rb(I), which was ascribed to the effective recognition of NonCalix[4]C6 for Cs(I). The optimum acidity in the extraction of Cs(I) was 4.0 mol·kg–1 HNO3. The extraction property and mechanism of Cs(I) were discussed. The composition of the extracted species of Cs(I) with NonCalix[4]C6 was determined as CsNO3·NonCalix[4]C6. Valuable chemical engineering parameters in the extraction of Cs(I) were obtained. It is beneficial to effectively partition Cs(I) from highly active liquid waste with the NonCalix[4]C6/1-octanol extraction system.

The adsorption behavior of Cs(I), one of the heat generators, in HNO3 medium was investigated at 298 K. The impact of U(VI), some typical elements, and temperature on the adsorption of Cs(I) was evaluated. It was performed by macroporous silica-based 1,3-[(2,4-diethylheptylethoxy)oxy]-2,4-crown-6-calix[4]arene (Calix[4]arene-R14) impregnated supramolecular recognition materials (Calix[4] + M)/SiO2–P. They were modified with tri-n-butyl phosphate (TBP), octanol (Oct), and methyloctyl-2-dimethylbutanemide (MODB). The excellent adsorption ability and high selectivity of (Calix[4] + M)/SiO2–P for Cs(I) except Rb(I) and U(VI) were confirmed. The adsorption ability of Cs(I) onto the modified supramolecular recognition materials was (Calix[4] + Oct)/SiO2–P > (Calix[4] + TBP)/SiO2–P > (Calix[4] + MODB)/SiO2–P. The chromatographic separation of Cs(I) from a 4.0 M HNO3 solution containing La(III), Sr(II), Ru(III), Cs(I), Rb(I), U(VI), Mo(VI), Zr(IV), Gd(III), and Pd(II) was carried out with a (Calix[4] + TBP)/SiO2–P packed column. Cs(I) was eluted effectively with water. The possibility and feasibility of effective partitioning of Cs(I) from highly active liquid waste by the (Calix[4] + M)/SiO2–P materials was evaluated.

A new multidentate soft-ligand 2,6-bis(5,6-dinonyl-1,2,4-triazine-3-yl)pyridine (NonBTP) was synthesized. The solvent extraction of Pd(II) and some typical metals Ru(III), Mo(VI), Fe(III), Co(II), Zr(IV), and Ni(II) with NonBTP/30 % 1-octanol–70 % 1-dodecane was investigated at 298 K. It was performed by examining the effects of contact time and the concentration of HNO3 in the range of (0.42 to 5.11) M. NonBTP showed a strong extraction ability and high selectivity for Pd(II) over the tested metals, which had very weak or almost no extraction. The optimum acidity in the extraction of Pd(II) was around 3.0 M HNO3. It was ascribed to the complexation of Pd(II), a weak Lewis acid and an electron-pair acceptor, with nitrogen inside NonBTP, a weak Lewis base and an electron-pair donor. The extraction of NonBTP for Pd(II) was an exothermic reaction. The composition of the extracted species was determined to be Pd(NO3)2·2NonBTP. Considering the excellent complexation of minor actinides MAs(III) with NonBTP, the results are beneficial to simultaneous partitioning of MA(III) and Pd(II) from highly active liquid waste by the NonBTP-containing extraction system.

A macroporous silica-based 2,6-bis(5,6-di(iso-hexyl)-1,2,4-triazine-3-yl)pyridine (BDIHTP) multinitrogen molecular recognition material, BDIHTP/SiO2-P, was prepared. It was performed through impregnation and immobilization of BDIHTP into the pores of the macroporous SiO2-P particle support with a mean diameter of 50 μm. The adsorption of some typical alkali metal and alkaline earths Cs(I), Na(I), K(I), Rb(I), Sr(II), and Ba(II), as well as Pd(II), a representative of precious metals, contained in highly active liquid waste (HLW), onto the BDIHTP/SiO2-P material was investigated at 298 K. It was carried out by examining the effects of contact time and the HNO3 concentration in the range 0.3–5.0 M. BDIHTP/SiO2-P showed excellent adsorption ability and high selectivity for Pd(II) over all the tested metals, which had weak or almost no adsorption. It was attributed to the strong chemical complexation of Pd(II), a soft Lewis acid and an electron-pair acceptor, with nitrogen inside BDIHTP, a soft Lewis base and an electron-pair donor. On the basis of the related results, the chromatographic separation of Pd(II) from 1.0 M HNO3 solution containing the tested metals was performed by BDIHTP/SiO2-P packed column. Pd(II) was effectively eluted with 0.2 M thiourea and separated from the others. The results are very beneficial to building an effective partitioning of minor actinides and Pd(II) together from HLW by the BDIHTP/SiO2-P materials.

A macroporous silica-based 1,3-[(2,4-diethylheptylethoxy)oxy]-2,4-crown-6-calix[4]arene (Calix[4]arene-R14) supramolecular recognition polymeric composite, (Calix[4] + MODB)/SiO2−P, was synthesized. The synthesis was performed by impregnation and immobilization of Calix[4]arene-R14 and methyloctyl-2-dimethylbutanemide (MODB) molecules in the pores of a macroporous SiO2−P polymeric particle support with a mean diameter of 50 μm. MODB was used to modify the Calix[4]arene-R14 through intermolecular interaction force. The static-state adsorption of some typical alkali metals and alkaline-earth metals such as Na(I), K(I), Cs(I), Rb(I), Sr(II), and Ba(II) onto (Calix[4] + MODB)/SiO2−P was investigated. The effects of contact time, HNO3 concentration in the range of 0.3−7.0 M, and temperature on the adsorption were examined. (Calix[4] + MODB)/SiO2−P exhibited strong adsorption ability and excellent selectivity for Cs(I) over all tested elements, which showed weak or almost no adsorption except for Rb(I). The adsorption onto (Calix[4] + MODB)/SiO2−P of the tested metals in HNO3 medium was exothermic. The thermodynamic parameters for the adsorptions of Cs(I) and Rb(I) were determined. It was found that, in 3.0 M HNO3, application of the (Calix[4] + MODB)/SiO2−P polymeric composite in the partitioning of Cs(I), one of the heat generators, from highly active liquid waste in the SPEC (strontium/cesium partitioning from HLW by extraction chromatography) process is promising.

To develop a separation process of Sr(II), a macroporous silica-based 4,4′,(5′)-di(tert-butylcyclohexano)-18-crown-6 (DtBuCH18C6) polymeric material, (DtBuCH18C6+Oct)/SiO2-P, was synthesized by impregnating and immobilizing DtBuCH18C6 and 1-octanol into the pores of the macroporous SiO2-P particles support. DtBuCH18C6 was modified with 1-octanol through hydrogen bonding. The adsorption of simulant elements of some typical fission products Ru(III), Pd(II), Ba(II), Mo(VI), La(III), Y(III), Sr(II), Cs(I) and those of non-fission products Na(I) and K(I) onto (DtBuCH18C6+Oct)/SiO2-P were studied at 298 K. The effects of the HNO3 concentration in a range of 0.1–5.0 M and contact time on the adsorption were investigated. (DtBuCH18C6+Oct)/SiO2-P showed excellent adsorption ability and high selectivity for Sr(II) over all of the tested metals except Ba(II). Partitioning of Sr(II) from a 2.0 M HNO3 solution containing ~5.0 × 10−3 M of the tested metals was conducted utilizing (DtBuCH18C6+Oct)/SiO2-P packed column. Pd(II), Mo(VI), Y(III), La(III), Ru(III), K(I), Cs(I), and Na(I) showed no adsorption and flowed into effluent along with 2.0 M HNO3. Sr(II) was retained on (DtBuCH18C6+Oct)/SiO2-P and was eluted effectively by H2O, while Ba(II) showed similar elution behavior. The bleeding of total organic carbon leaked from (DtBuCH18C6+Oct)/SiO2-P was evaluated. It was demonstrated that the macroporous silica-based (DtBuCH18C6+Oct)/SiO2-P materials are promising in separation of Sr(II) from high level radioactive waste.

A novel macroporous silica-based supramolecular recognition compound 1,3-[(2,4-diethyl heptylethoxy)oxy]-2,4-crown-6-Calix[4]arene (Calix[4]arene-R14) polymeric composite (Calix[4] + Oct)/SiO2-P was prepared. It was synthesized by impregnating and immobilizing a mixture of Calix[4]arene-R14 and n-octanol into the pores of the macroporous SiO2-P particles. The adsorption of Cs(I) and some typical fission and non-fission products (FPs) contained in high level liquid waste (HLLW) such as Na(I), K(I), Cs(I), Rb(I), Sr(II), and Ba(II) onto (Calix[4] + Oct)/SiO2-P was investigated by examining the influence of contact time and the HNO3 concentration at 298 K. It was found that with an increase in the concentration of HNO3, the adsorption of Cs(I) onto (Calix[4] + Oct)/SiO2-P increased from 0.324 M to 4.0 M HNO3 and then decreased to 7.0 M HNO3. At the optimum HNO3 concentration of 4.0 M HNO3, (Calix[4] + Oct)/SiO2-P showed excellent adsorption ability and high selectivity for Cs(I) over all of the tested elements except Rb(I). The chromatographic separation of Cs(I) from a simulated HLLW containing ∼5.0 mM of the tested elements was performed by (Calix[4] + Oct)/SiO2-P packed column at 298 K. Na(I), K(I), Sr(II), and Ba(II) showed no adsorption and were eluted into effluent along with 4.0 M HNO3. Cs(I) and Rb(I) adsorbed by (Calix[4] + Oct)/SiO2-P could be effectively eluted with water and separated from the others. It is demonstrated that (Calix[4] + Oct)/SiO2-P is promising to apply in the separation of Cs(I), one of the heat emitting nuclides, from an acidic HLLW by extraction chromatography.

4,4′,(5′)-Di-(tert-butylcyclohexano)-18-crown-6(DtBuCH18C6) is a chelating agent having high selectivity mostly for Sr(II). To significantly reduce its leakage by molecular modification, a macroporous silica-based DtBuCH18C6 polymeric composite (DtDo/SiO2–P) was synthesized. It was performed by impregnating and immobilizing DtBuCH18C6 and 1-dodecanol molecules into the pores of the SiO2–P particles utilizing an advanced vacuum sucking technique. The adsorption of a few fission and non-fission products Sr(II), Ba(II), Cs(I), Ru(III), Mo(VI), Na(I), K(I), Pd(II), La(III), and Y(III) onto DtDo/SiO2–P was investigated. It was done by examining the effects of contact time and the HNO3 concentration in a range of 0.1–5.0 M at 298 K. At the optimum concentration of 2.0 M HNO3, DtDo/SiO2–P exhibited strong adsorption ability and high selectivity for Sr(II) great over all of the tested elements, which showed very weak or almost no adsorption except Ba(II). Meanwhile, It was found that the quantity of total organic carbon (TOC) leaked from DtDo/SiO2–P in 2.0 M HNO3, 187.5 ppm, was lower than 658.4 ppm that leaked from DtBuCH18C6/SiO2–P, which was not modified. This was ascribed to the effective association of DtBuCH18C6 and 1-dodecanol through intermolecular interaction. The reduction of DtBuCH18C6 leakage by molecular modification with 1-dodecanol was achieved. It was of great benefit to application of DtDo/SiO2–P 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 the MAREC (Minor Actinides Recovery from HLLW by Extraction Chromatography) process developed recently.

A novel macroporous silica-based chelating polymeric composite, DtDo/SiO2–P, was synthesized by molecular modification of 4,4′,(5′)-di-(tert-butylcyclohexano)-18-crown-6 (DtBuCH18C6) with a long carbon chain organic compound 1-dodecanol. It was performed through impregnation and immobilization of DtBuCH18C6 and 1-dodecanol molecules into the pores of the SiO2–P particles. The adsorption of a few fission and non-fission product elements Sr(II), Ba(II), Cs(I), Ru(III), Mo(VI), Na(I), K(I), Pd(II), La(III), and Y(III) onto DtDo/SiO2–P was investigated at 323 K. The effects of contact time and the HNO3 concentration in a range of 0.1–4.0 M were investigated. It was found that at the optimum concentration of 2.0 M HNO3, DtDo/SiO2–P exhibited strong adsorption ability and excellent selectivity for Sr(II) over all of the tested elements, which showed very weak or almost no adsorption except Ba(II). The bleeding of total organic carbon (TOC) from DtDo/SiO2–P was evaluated. The quantity of TOC in aqueous phase increased with an increase in HNO3 concentration in terms of a linear equation [TOC] = 35.82[HNO3] + 115.5 with a correlation coefficient of 0.9751. The TOC content leaked from DtDo/SiO2–P modified by 1-dodecanol, 119.0–269.3 ppm, in the range of 1.0–4.0 M HNO3 was significantly lower than that of 424.8–634.6 ppm in the case without modification. It resulted from the intermolecular interaction force of DtBuCH18C6 and 1-dodecanol through hydrogen bonding. The reduction of DtBuCH18C6 leakage by molecular modification was achieved. It is of great benefit to application of DtDo/SiO2–P in partitioning of Sr(II), one of the main heat generators, from high level liquid waste (HLLW) in reprocessing process of nuclear spent fuel in MAREC (Minor Actinides Recovery from HLLW by Extraction Chromatography) process developed.

A macroporous silica-based octyl(phenyl)-N,N-diisobutylcarbamoylmethylphoshine oxide (CMPO) chelating polymeric composite, CMPO/SiO2−P, was synthesized by impregnating and immobilizing CMPO into the pores of SiO2−P particles support. To separate long-lived minor actinide (MA(III)) elements such as Am(III) and Cm(III) from highly active liquid waste (HLW), the adsorption and elution of 13 representative simulated fission products from a 3.0 M HNO3 were performed. It was carried out through two columns, both packed with CMPO/SiO2−P at 323 K. In the first column, all of the simulated elements were separated into three groups: (1) Cs(I), Sr(II), and a portion of Ru(III) (nonadsorption group); (2) Pd(II), a portion of Zr(IV), and all of REs(III) (MA-RE−Pd-Zr group); and (3) most of Zr(IV), Mo(VI), and a portion of Ru(III) (FPs group) by eluting with 3.0 M HNO3, H2O, and 0.5 M H2C2O4, respectively. MA(III) were predicted to flow into the second group along with Gd(III) because of their close adsorption and elution behaviors onto CMPO/SiO2−P. By addition of 0.5 M DTPA and conditioning of the HNO3 concentration to 3.0 M, the MA(III)-containing effluent was then supplied to the second column and separated into (1) Pd(II), (2) RE(III) elements Sm(III), Eu(III), Gd(III), and Y(III) (MA-RE group), and (3) Zr(IV) by eluting with 3.0 M HNO3, H2O, and 0.5 M H2C2O4, respectively. MA(III) flowed into the MA-RE group along with Gd(III). Based on the position of MA(III) in the elution curves, an effective group partitioning process of MA(III) and RE(III) from HLW by extraction chromatography was proposed.

To partition effectively Cs(I) and Sr(II), two harmful heat emitting nuclides, from a highly active liquid waste by extraction chromatography, two kinds of macroporous silica-based polymeric materials, Calix[4]arene-R14/SiO2-P and TODGA/SiO2-P, were synthesized. Two chelating agents, 1,3-[(2,4-diethyl-heptylethoxy)oxy]-2,4-crown-6-calix[4]arene (Calix[4]arene-R14), an excellent supramolecular compound having molecular recognition ability for Cs(I), and N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) were impregnated and immobilized into the pores of SiO2-P particles support by a vacuum sucking technique. The loading and elution of 11 typical simulated fission and non-fission products from 4.0 M or 2.0 M HNO3 were performed at 298 K. It was found that in the first column packed with the Calix[4]arene-R14/SiO2-P, all of the simulated elements were separated effectively into two groups: (1) Na(I), K(I), Sr(II), Fe(III), Ba(II), Ru(III), Pd(II), Zr(IV), and Mo(VI) (noted as Sr-group); (2) Cs(I)–Rb(I) (Cs-group) by eluting with 4.0 M HNO3 and distilled water, respectively. The harmful element Cs(I) flowed into the second group along with Rb(I) because of their close sorption and elution properties towards Calix[4]arene-R14/SiO2-P, while Sr(II) showed no sorption and flowed into Sr-containing group. In the second column packed with TODGA/SiO2-P, the Sr-group was separated into (1) Ba(II), Ru(III), Na(I), K(I), Fe(III), and Mo(VI) (non-sorption group); (2) Sr(II); (3) Pd(II); and (4) Zr(IV) by eluting with 2.0 M HNO3, 0.01 M HNO3, 0.05 M DTPA–pH 2.5, and 0.5 M H2C2O4, respectively. Sr(II) adsorbed towards TODGA/SiO2-P flowed into the second group and showed the excellent separation efficiency from others. Based on the elution behavior of the tested elements, an advanced PREC (Partitioning and Recovery of two heat generators from an acidic HLW (high activity liquid waste) by Extraction Chromatography) process was proposed.

Through an advanced vacuum sucking technique, two macroporous silica-based N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) and octyl(phenyl)-N,N-diisobutylcarbamoyl-methylphoshine oxide (CMPO) polymeric composites, TODGA/SiO2-P and CMPO/SiO2-P, were synthesized by impregnating and immobilizing the chelating agents into the pores of the SiO2-P particles. To partition long-lived minor actinides (MA(III)), such as Am(III) and Cm(III) from highly active liquid waste (HLW), the loading and elution of 15 typically simulated fission and non-fission products from a 3.0 M HNO3 were performed. In the first column packed with TODGA/SiO2-P, the simulated elements were effectively separated into following groups: (1) non-adsorption group, (2) MA–lRE–FPs group, (3) hRE group, and (4) micro quantity of Zr(IV). MA(III) was predicted to flow into the second group along with Nd(III) due to their close adsorption and elution onto TODGA/SiO2-P. In the second column packed with CMPO/SiO2-P, after conditioning the acidity in MA–lRE–FPs containing 0.05 M DTPA to 3.0 M HNO3, it was separated into (1) Sr(II) and Pd(II), (2) MA–mRE, (3) lRE, and (4) Zr(IV). MA(III) was believed to flow into MA–mRE effluent along with Gd(III) because of the similar adsorption towards CMPO/SiO2-P. In terms of the position of MA(III) appeared, an improved MAREC process for long-lived MA(III) partitioning from HLW was proposed.

A macroporous silica-based N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) polymeric composite (TODGA/SiO2-P) was synthesized. It was done through impregnation and immobilization of TODGA molecule into the pores of the SiO2-P particles utilizing a vacuum sucking technique. The macroporous SiO2-P particles were the silica-based organic/inorganic composite synthesized by immobilizing styrene–divinylbenzene copolymer inside SiO2 through the complicated polymerization reaction. The adsorption of rare earth (RE(III)) elements onto TODGA/SiO2-P was investigated in HNO3 solution containing diethylenetriaminepentaacetic acid (DTPA), an acidic multi-dentate chelating agent. It was found that in the presence of 0.05 M DTPA, NO3- and H+ had significant effect on the TODGA/SiO2-P adsorption due to the competition reactions of RE(III) with different species, H4DTPA− and H2DTPA3−. With an increase in the concentration of NO3- from 0.115 M to 3.015 M, the adsorption of RE(III) onto TODGA/SiO2-P increased noticeably. On the other hand, RE(III) showed strong adsorption at 0.1 M H+, weak adsorption at around pH 2, and no adsorption in excess of pH 2.3. In a 0.1 M H+–0.115 M NO3-–0.05 M DTPA solution, a change of the distribution coefficient of RE(III) onto TODGA/SiO2-P with an increase in atomic number of RE(III) from La(III) to Lu(III) was investigated. The silica-based TODGA/SiO2-P polymeric composite showed strong adsorption for heavy RE(III) over the light one. In a 0.01 M H+–1.0 M NO3-–0.05 M DTPA solution, the effect of the ratio of solid phase to liquid one on the relationship of the distribution coefficient of RE(III) with the change in atomic number of RE(III) was also studied. Based on the complicated disassociation equilibrium of DTPA, the influence of the concentrations of NO3- and H+ on the adsorption of TODGA/SiO2-P for RE(III) was demonstrated. This makes the partitioning of RE(III) and MA(III) together from high level liquid waste (HLLW) by the polymeric composite TODGA/SiO2-P promising.

A novel macroporous silica-based 2,6-bis(5,6-diisobutyl-1,2,4-triazine-3-yl)pyridine (iso-Bu-BTP), a neutral chelating agent having several softatom nitrogen, polymeric composite (iso-Bu-BTP/SiO2-P) was synthesized. It was done through impregnation and immobilization of iso-Bu-BTP molecule into the pores of SiO2-P particles with 40–60 μm of bead diameter and 0.6 μm of mean pore size. The effective impregnation resulted from the intermolecular interaction of iso-Bu-BTP and co-polymer inside the SiO2-P particles by a vacuum sucking technique. To understand the possibility of applying iso-Bu-BTP in the MAREC process developed, the adsorption behavior of a few representative rare earths (REs) such as Ce(III), Nd(III), Gd(III), Dy(III), Er(III), Yb(III), and Y(III) towards iso-Bu-BTP/SiO2-P was investigated at 298 K. The influence of the HNO3 concentration in a wide range of pH 5.52–3.0M and a few chelating agents such as formic acid, citric acid, and diethylenetriaminepentaacetic acid (DTPA) on the adsorption of RE(III) was examined. It was found that in the presence of chelating agent, the adsorption ability of the tested RE(III) towards iso-Bu-BTP/SiO2-P decreased due to two competition reactions of RE(III) with iso-Bu-BTP/SiO2-P and chelating agents. In a 0.01M HNO3 solution containing 1M formic acid or 1M citric acid, light RE(III) showed lower adsorption towards iso-Bu-BTP/SiO2-P than that of the heavy one. This makes the separation of light RE(III) from the heavy one possible. Based on the similarity of minor actinides and heavy RE(III) in chemical properties and the results of column separation experiments, chromatographic partitioning of light RE(III) from a simulated high level liquid waste solution composed of the heavy RE(III) and minor actinides in MAREC process is promising.