P. Kandwal

A novel CMPO-functionalized task specific ionic liquid: synthesis, extraction and spectroscopic investigations of actinide and lanthanide complexes

A novel CMPO (carbamoylmethylphosphine oxide) based task specific ionic liquid (TSIL) with an NTf(2)(-) counter anion was synthesized and evaluated for actinide/lanthanide extraction from acidic feed solutions using several room temperature ionic liquids (RTILs). The extraction data were compared with those obtained with CMPO in the same set of RTILs and also in the molecular diluent, n-dodecane. The extracted species were analyzed by the conventional slope analysis method and the extraction followed an ion-exchange mechanism. The nature of bonding in the extracted complexes was investigated by various spectroscopic techniques such as FT-IR and UV-visible spectroscopy.

Separation of Carrier Free 90Y from 90Sr by Hollow Fiber Supported Liquid Membrane Containing Bis(2-ethylhexyl) Phosphonic Acid

The present article gives a comparative account of the efficiency of carrier-free 90Y separation from 90Sr by solvent extraction, flat sheet-supported liquid membrane (FSSLM) and hollow fiber-supported liquid membrane (HFSLM) methods using bis(2-ethylhexyl) phosphonic acid (PC88A) as the carrier extractant. The major focus of this work has been to develop the HFSLM method for the separation of Y(III) on a relatively large scale. The feed and receiver phase conditions were optimized by carrying out batch solvent-extraction studies. The extraction of Sr(II) by PC88A was negligible in the acidity range of 0.01–3 M HNO3, whereas the extraction of Y(III) was significantly large at lower acidity (≤0.1 M HNO3) with a separation factor (SF = DY/DSr) of 8.5 × 104. HFSLM studies suggested selective and efficient transport of Y(III) into 3 M HNO3 from a feed solution containing a mixture of Y(III) and Sr(II) at 0.1 M HNO3. On the other hand, transport of Sr(II) was negligible in the receiver phase. The purity of the separated 90Y was ascertained by paper chromatography and by half-life measurement. The radiation stability of the carrier was excellent as studied up to 1000 KGy dose.

Selective caesium transport using hollow fibre-supported liquid membrane containing calix[4]arene-bis-naphthocrown-6 as the carrier extractant

Abstract Polypropylene hollow fibre-based supported liquid membrane (HFSLM) containing calix[4]-bis-2,3-naphtho-crown-6 in 20% (v/v) n-dodecane+80% (v/v) 2-nitrophenyl octyl ether (NPOE) as the carrier solvent was employed for the first time to investigate the transport behaviour of radio-caesium. The carrier solution was 1 mM calix[4]-bis-2,3-naphtho-crown-6 in 20% (v/v) dodecane+80% (v/v) NPOE+0.4% alamine 336 and the feed was 3 M HNO3 while distilled water was used as the receiver phase. In spite of high viscosity of the carrier solvent, quantitative (>99%) transport was possible in about 6 h. Significant amount of acid transport was also noticed which was ascribed to a co-transport mechanism involving encapsulated hydronium ion. Selectivity studies were carried out by taking a mixture of radiotracers, viz. 51Cr, 59Fe, 85,89Sr, 137Cs, 152,154Eu and 241Am, which represent some of the elements present in the high level waste, in the feed solution. The decontamination factors for various metal ions were found to be in the range 540–890. High decontamination factors as well as possibility of working over several days without deterioration of the liquid membrane suggested possible application of the system for the recovery of radio-caesium from high level waste. Studies on the membrane stability indicated reproducible transport data over 40 h.

Selective Recovery of Am(III) over Eu(III) by Hollow Fiber Supported Liquid Membrane Using Cyanex 301 in the Presence of Synergists as the Carrier

Lanthanide/actinide separation was investigated on 0.5 L scale (both feed and receiver phase volumes) with Cyanex-301 (bis(2,4,4-trimethylpentyl)dithiophosphinic acid) as the carrier using the Hollow Fiber Supported Liquid Membrane (HFSLM) technique under varying feed pH conditions. At pH 3.4, the quantitative transport of Am(III) was achieved within 15 minutes with 0.5 M Cyanex 301 as the carrier with separation factor of >100 over Eu(III). The transport rate of Am(III) decreased significantly with increasing feed acidity, and was independent of the feed nitrate concentration. The effect of neutral auxiliary donor ligands as synergists, viz. tri-n-butyl phosphate (TBP), N,N,-dihexyl octanamide (DHOA) and 2,2′-bipyridyl (Bipy) on the selective recovery of Am(III) over lanthanides was also investigated. The presence of synergists led to the possibility of Am(III) recovery at lower pH values with improved separation factors (SF). It was particularly beneficial as the use of buffer for feed pH adjustment could be avoided. In the presence of synergists, >85% transport of Am(III) was achieved in 30 minutes of operation at pH 2.0. The SF value at pH 2.0 for different synergists followed the order: bipyridyl (350) >DHOA (50) >TBP (8). The transport rate of Am(III) by HFSLM system was found to be satisfactory for 25 hours of continuous operation. However, the SF values deteriorated significantly with the time of operation.

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.

A ‘cold’ actinide partitioning run at 20 L scale with hollow fibre supported liquid membrane using diglycolamide extractants

Abstract ‘Actinide partitioning’ studies were attempted by hollow fibre supported liquid membrane (HFSLM) technique using pressurized heavy water reactor simulated high level waste (PHWR-SHLW) as the feed. Two diglycolamide extractants for actinide partitioning, viz. 0.1 M TODGA (N,N,N´,N´-tetraoctyl diglycolamide) + 0.5 M DHOA (N,N-dihexyl octanamide) and 0.2 M T2EHDGA (N,N,N´,N´-tetra-2-ethylhexyl diglycolamide) + 30% iso-decanol in n-dodecane were used as the carrier solvent. Quantitative recovery of all trivalent actinides and lanthanides from PHWR-SHLW was achieved with both the carriers within 30 min when the feed volume was 0.5 L. On the other hand, about 18 h were necessary for a similar study carried out using a feed volume of 20 L. None of the other elements present in the PHWR-SHLW were transported, except small quantities of Sr and Mo. The product could be concentrated to two and four times by maintaining the feed to receiver phase volume ratio of 2:1 and 4:1, respectively. The transport behaviour of trivalent actinides and lanthanides by the two diglycolamide extractants were remarkably similar. The present studies revealed that diglycolamide-HFSLM system offers a promising alternative approach for ‘actinide partitioning’, where the use of organic solvent inventory could be drastically reduced. A mathematical model was developed and there was good agreement between the predicted and experimentally obtained data.

A Novel Liquid Emulsion Membrane Containing TODGA as the Carrier Extractant for Am Recovery from Acidic Wastes

The recovery of Am has been investigated by Liquid Emulsion Membrane (LEM) containing 0.1 M N,N,N′,N′-tetraoctyl-3-oxapentane diamide (TODGA) + 0.5 M di-n-hexyloctanamide (DHOA) in n-dodecane as extractant. Span 80 (sorbitan monooleate) was used as the surfactant for making the emulsion while 3 M HNO3 and 0.1 M acetate buffer (at pH 4.75) were used as the external and internal phases, respectively. Optimized conditions indicated 2% Span 80 was required for making the emulsions. The effect of different experimental conditions such as varying feed acidity, varying volume ratio, different strippants, and varying TODGA concentration have been studied for the quantitative removal of Am from acidic solution. The higher transport rate has been observed which can be attributed to the higher surface area per unit volume available for mass transport. Demulsification was possible by heating the emulsions to 80°C. Actual acidic radioactive waste has also been tested for the recovery of americium. The results show the applicability of ELM for the removal of Am(III) from waste solutions with a faster rate of transport as compared to those reported previously.