Selective extraction of mercury by 4-phenyl-5-p-tolyl-1,3,4-thiadiazolium-2-thiolate (PTTDT)

The extraction of radio-mercury(II) by PTTDT was investigated as function of diluent, hydrochloric acid concentration, extractant concentration and certain foreign compounds in the aqueous phase. The extraction was found to be quantitative when chloroform was used as diluent and at low HCl or high PTTDT concentrations. Neither the presence of boric acid, nor several metal salts (NaF, CuSO₄, ZnSO₄ or Na₂SO₄) had any effect on the E%. The presence of chloride or bromide lowers the E% considerably. A radiochemical procedure was developed to pre-concentrate mercury from artifical sea water using an organic: aqueous phase ratio of 1∶100.     

Evaluating the residence time for cesium removal from simulated Hanford tank wastes using SuperLig® 644 resin

Batch contact and column experiments were performed to evaluate the effect of residence time on cesium removal from two simulated Hanford tank wastes using SuperLig^® 644 resin. The two waste simulants mimic the compositions of tanks 241-AZ-102 and 241-AN-107 at the U.S. Department of Energy (DOE) Hanford site. A single column made of glass tube (2.7-cm i.d.), which contained ~100 ml of H-form SuperLig^® 644 resin was used in the column experiments. The experiments each consisted of loading, elution, and regeneration steps were performed at flow rates ranging from 0.64 to 8.2 BV/h for AZ-102 and from 1.5 to 18 BV/h for AN-107 simulant. The lowest flow rates of 0.64 and 1.5 BV/h were selected to evaluate less than optimal flow conditions in the plant. The range of the flow rates is consistent with the River Protection Project design for the waste treatment plant (WTP) columns, which will operate at a flow rate between 1.5 to 3 BV/h. Batch contact experiments were also performed for two batches of SuperLig^® 644 to determine the equilibrium distribution coefficients (K _d) as a function of Cs concentration. The column experiments revealed that adequate column loading for Cs on SuperLig^® 644 (50% breakthrough at 100 bed volumes) can be achieved for the two simulated Hanford tank wastes at the nominal plant flow rates of 1.5 and 3 BV/h (residence times 40 and 20 minutes). The column performance was marginally improved at flow rates below the nominal rates. At flow rates higher than the nominal, the Cs loading deteriorated significantly. The SuperLig^® 644 was eluted effectively with 0.5M nitric acid. The elution required approximately 15 BVs to reduce Cs concentration to below 1% of initial Cs concentration in the feeds.     

Fast and simple radiochemical method for the separation of uranium,thorium and lanthanum

The concept of using paper chromatography on papers impregnated with liquid anion or cation exchangers is extended to the separation of trace elements through filtration on filter papers loaded with suitable extractant. The uptake of uranium, thorium and lanthanum from HCl and HNO₃ media of different molarities by a filter paper treated with tri-octyl amine (TOA) is investigated. The effect of the different parameters on the uptake of the studied elements is experimented. A simple and fast radiochemical procedure is developed for the separation of La, Th and U from each other.     

Alkenyl selenols and selenocyanates: synthesis, spectroscopic characterization by photoelectron spectroscopy, and quantum chemical study

Vinyl, allyl, and homoallyl selenols were easily prepared by a chemoselective reduction of the corresponding selenocyanates with aluminum hydrides. Two stable vinyl and five stable allyl conformers of both series were predicted on the potential-energy surface. The interaction of SeH or SeCN groups with the vinyl group has been investigated with UV photoelectron spectroscopy and quantum chemical calculations, using the MP2/cc-pVTZ and B3LYP/cc-pVTZ levels. In the vinyl derivatives, a surprisingly strong direct conjugation of the selenium lone electron pair and the C=C double bond was observed. On the other hand, in allyl position the selenium lone pair is independent on the C=C double bond, and the hyperconjugation between the Se-C bond and the double bond is the ruling effect. Thus is clarified the type and extent of the interaction between the SeH or SeCN group and the unsaturated moiety.     

O-silylated enolate phenylthialkylation: A synthesis of α,β-unsaturated 5- and 6-membered lactones.

ZnBr₂-catalysed phenylthioalkylation of ketene bis(trimethylsilyl)acetals, obtained from carboxylic acids, with appropriate α-chlorosulphides can be used to prepare γ- and δ- lactones.     

Barrier to internal rotation in 2,3- and 3,3-difluoropropenal and their methyl derivatives

The conformational stability and structure of 2,3-dimethylpropenal, 2,3-difluoropropenal and their 3,3-dimethyl and 3,3-difluoro derivatives were investigated utilizing ab initio calculations with 3-21G and 6-31G basis sets. For 2,3-dimethylpropenal and 3,3-difluoropropenal the s-trans was predicted to be the low-energy form. In the case of 3,3-dimethylpropenal and 2,3-difluoropropenal the s-cis was predicted by both levels of calculation to be the more stable conformer. Full optimization was performed at the transition states and the barriers to internal rotation were calculated. Methyl and fluorine substitution were found to significantly increase the barrier to interconversion in propenal. The relative change in the barrier depends on the position and the type of the substituent. The trans to cis barrier in 2,3-dimethylpropenal was calculated to be about 3 kcal mol⁻¹ greater than that in 3,3-dimethylpropenal, while the cis to trans barrier in 2,3-difluoropropenal was predicted to be about 7 kcal mol⁻¹ higher than the corresponding one in 3-3-difluoropropenal.     

Separation of strontium from simulated waste in K2SO4/Nitrate medium containing Sr2+, Eu3+, Ce3+, Pd2+, Rh3+, Ru3+, UO 2 2+ , Fe3+, Cr3+, Ni2+, Al3+, Ca2+ and Cs+, by strongly basic anion exchanger

In this work Strontium was separated selectively form, Pd²⁺, Ni²⁺ and Ca³⁺ using anionic resins of Amberlite type IRA-900 and IRA-410 from nitrate medium. The Separation of strontium by strongly basic anion exchangers IRA-410 and IRA-900 from simulated waste containing, Sr²⁺, Eu³⁺, Ce³⁺, Pd²⁺, Rh³⁺, Ru³⁺, VO₂ ²⁺, Fe³⁺, Cr³⁺, Ni²⁺, Al³⁺, Ca²⁺, and Cs⁺, in K₂SO₄/nitrate medium which adsorbed as strontium sulphate complex was achieved through ligand- ligan exchange. The elution of strontium carried out via “loading” the column with a solution of 0.03N EDTA in presence of 0.1N NaNO₃ at pH7 where Sr²⁺ has low K_d value. An inductively Coubled Plasma — Optical Emission Spectrometry (ICP — OES) of ARL type model 3520, was used for elemental analysis.     

Influence of diluent on the synergic extraction of divalent cobalt by the thenoyltrifluoroacetone-tribenzylamine perchlorate system

The effect of ten pure diluents and different mixtures of nitrobenzene and toluene on the synergic extraction of Co²⁺ by the thenoyltrifluoroacetone (HTTA)-tribenzylamine (TBA) mixture is studied. The logarithm of the extraction constant of Co(TTA)₂ increases with increasing dielectric constant of the diluent, whereas the logarithm of the formation constant of the extracted adduct Co(TTA)₂TBA decreases with increasing dielectric constant of the diluent. This behaviour is explained by changes in the hydrophobic character of the extracted species. The theory of regular solutions is successfully applied to the extracted adduct. Consideration of the self-association of the amine salt is necessary in the treatment of the equilibria involved.     

Determination of trace elements in Egyptian molasses by instrumental neutron activation analysis

Multielement neutron activation analysis has been applied to the determination of macro, micro and trace amounts of Al, Br, Ca, Cl, Co, Cr, Cs, Fe, K, La, Mg, Mn, Na, Rb, Sc and V in molasses of Kom Ombo, Edfu, Armant, Naga Hammady and Abu Korkass cane sugar factories. The threshold element concentrations are acceptable and below the safety. Differences in element concentrations may be related to different botanic textures and structures, different compositions of sugar cane plants, corrosion of containers or changes in soil as a result of geochemical differentiation. The method is sensitive down to 0.038 ppm of V. The relative errors due to counting statistics are in the range of 0.2–11%.     

Complexes of tris(o-phenanthroline)nickel(II) and copper(II) bromide with dithiocarbamates derived from α-amino acids

Complexes of 1,10-o-phenanthroline (o-phen)-Ni^II and Cu^II with dithiocarbamates derived from -amino acids (glycine, phenylalanine, alanine, methionine and tryptophan) were synthesized and characterized by chemical analysis, spectral and thermal studies and by biological screening; the complexes are non-electrolytes. The empirical formula are [Ni(o-phen)₂(aadtc)] and [Cu₂(o-phen)₂(phaladtc)(H₂O)₂Br₂] where, aadtc = glycinyl-, phenylalaninyl-, alaninyl-, methioninyl- and tryptophanyldithiocarbamate and phaladtc = phenylalaninyldithiocarbamate. The structure of these complexes is probably octahedral. Molecular association through hydrogen bonding between the —NH and the carboxylate groups is proposed for the Ni^II complexes. The Cu^II complex is dimeric with the phenylalaninyldithiocarbamate acting as a bridge.