Formation of adducts between U(TTA)4 and several neutral donors was studied by spectrophotometry and it was shown that each of the neutral donors forms only 1∶1
adduct with U(TTA)4. The adduct formation constants with some neutral donors were determined for benzene and chloroform media. As these adducts
are involved in the synergistic extraction of U(IV) from aqueous media by mixtures of HTTA and neutral donors dissolved in
organic solvents, the extraction equilibrium constants were estimated, The adduct formation was found to result in an increase
of the co-ordination number of U(IV) from 8 in U(TTA)4 to 9 in the adducts it forms with the neutral donors. Similar absorption spectral studies with U(DBM)4 revealed that it forms much weaker adducts than the corresponding ones with U(TTA)4.
The extraction of Pu(IV) from perchloric acid by HTTA—TPPO mixtures employing benzene and chloroform as diluents has been
studied. While Pu(TTA)4·TPPO appears to be the dominant species with benzene, mixed adducts involving perchlorate ion formation seem to be predominant
in the extraction with chloroform. The adduct formation between Pu(TTA)4 and different neutral donors, in benzene, was studied by spectrophotometry and the constants of the 1∶1 adducts formed were
Synergistic extraction of tetravalent actinides, using mixtures of a β-diketone and several neutral organophosphorous extractants,
was recently demonstrated. In this work the extraction of the ions Th(IV), Np(IV) and Pu(IV), from perchloric acid medium,
by benzene solutions of a β-diketone, thenoyltrifluoroacetone (HTTA), in combination with a neutral organosulfoxide donor,
di-n-octyl sulfoxide (DOSO), has been investigated. Two methods viz. the slope analysis method and JOB's method have been
employed for the study. The species mainly responsible for the observed synergism, with the M(IV) ions studied, was found
to be M(TTA)4·DOSO. The extraction and adduct formation equilibrium constants are given.
Authors:M. Charyulu, D. Phal, D. Noronha, V. Ramakrishna, and V. Venugopal
The extraction of Am(III) from nitric, hydrochloric, oxalic, phosphoric and hydrofluoric acids was studied using 0.4F di-2-ethyl hexyl phosphoric acid (HDEHP) containing 0.1M phosphorous pentoxide (P2O5) in dodecane/xylene. The extraction with pure 0.4F HDEHP was found to be negligible from all the media studied. However, the presence of a small amount of P2O5 in it increased the extraction substantially. The distribution ratios of Am(III) obtained for HDEHP - P2O5 mixture 3M nitric acid containing different concentrations of oxalic acid/phosphoric acid/hydrofluoric acid are in the order of 200-250. The same for 3M hydrochloric acid is very high (800). These distribution ratios are sufficiently high for the quantitative extraction of Am(III) from all the acid media studied. Different reagents such as ammonium oxalate, sodium oxalate, oxalic acid, hydrofluoric acid, sodium carbonate and potassium sulphate were explored for the back extraction of Am(III) from 0.4F HDEHP + 0.1M P2O5 in dodecane/xylene. Of these, 0.35M ammonium oxalate and 1M sodium carbonate were found to be most suitable. The back extraction of Am(III) was also attempted with water and 1M H2SO4, HNO3, HClO4 and HCl solutions after allowing the extracted organics to degrade on its own. It was found that more than 90% of Am could be back extracted with these acids. Using this method more than 90% of Am(III) was recovered from nitric acid solutions containing calcium and fluoride ions.
Authors:V. Ramakrishna, S. Patil, L. Reddy, and A. Reddy
Extraction of Tm(III), from thiocyanate media, by different sulfoxides (R2SO) has revealed that the extractable complex is Tm(SCN)3·4 R2SO. When mixtures of DPSO and HTTA are used for the extraction of Tm(III) from thiocyanate or perchlorate media, synergistic
enhancement of the extraction of Tm(III) results. The complexes responsible for the enhanced extraction are Tm(TTA)3·DPSO and Tm(TTA)3·2 DPSO when perchlorate media were employed for the extraction and Tm(SCN)(TTA)2·2 DPSO and Tm(SCN)2(TTA)·3 DPSO, in addition to the above two when a thiocyanate medium was employed for the extraction. Values of equilibrium
constants for some equilibria encountered in the extraction of Am(III) and Tm(III) by mixtures of DPSO and HTTA are given.
Authors:A. Garg, V. Ramakrishna, Vivek Singh, and M. Olaniya
Solid wastes and sewage sludges in metropolitan cities are potential health hazards due to toxic heavy metal pollutants. Sewage sludges from six Indian cities viz., Ahmedabad, Bikaner, Bombay, Calcutta, Jaipur, Kanpur and solid wastes from six different disposal sites of the capital city of Delhi have been analyzed for 26 elements (As, Au, Ba, Br, Co, Cr, Cs, Cu, Eu, Fe, Hg, Hf, K, La, Mg, Mn, Mo, Na, P, Rb, Sb, Sc, Se, Sr, Th and Zn) by employing instrumental neutron activation analysis (INAA). Sewage sludges from Bombay after different treatments (settled, digested, aerobic, anaerobic) along with several environmental SRMs were also analyzed. An attempt has been made to attribute the pollutant sources to the degree of urbanisation and industrialization of the city. Role of treatment processes in the removal/retention of heavy metals is discussed.
Authors:D. Phal, S. Kannan, V. Ramakrishna, and S. Patil
Extraction of plutonium(IV) from aqueous sulfuric and sulfuric-nitric acid into di-2-ethylhexyl phosphoric acid (HY) in the diluents n-dodecane, toluene or chloroform has been investigated. The composition of the Pu(IV) species extracted from H2SO4 was found to be PuH2Y6, which changed to Pu(NO3)H2Y5 and Pu(NO3)2H2Y4 with increasing concentration of nitrate ion in the aqueous medium. These three species can be represented as PuY2(HY2)2, Pu(NO3)Y(HY2)2 and Pu(NO3)2(HY2)2, respectively, where Y represents the anion of monomeric HY, and HY2 the anion of dimeric H2Y2. Synergism in the extraction of Pu(IV) by the addition of thenoyltrifluoroacetone (HTTA) to HY was also investigated and attributed to extraction of the additional species, Pu(TTA)Y(HY2)2 and Pu(TTA)2(HY2)2. The addition of the neutral extractant tri-n-octylphosphine oxide (TOPO) to HY did not result in synergism in the extraction of Pu(IV) from aqueous sulfuric acid. With aqueous nitric acid under similar conditions, however, synergism was observed. The possible equilibria in these systems were identified and the corresponding equilibrium constants were determined.
Authors:S. Patil, V. Ramakrishna, P. Kartha, and N. Gudi
Solutions of HTTA are known to extract tetravalent actinides as M(TTA)4 species. When TOPO is added to HTTA solutions, the extracting of Np(IV) and Pu(IV) from aqueous perchloric acid was enhanced
enormously. The species responsible for the enhanced extraction were identified from the extraction data by the slope ratio
method and JOB's method. It was found that the predominant species responsible for enhancement in the extraction, when [HTTA]≫[TOPO],
was M(TTA)4. TOPO for both Np(IV) and Pu(IV). Furthermore, it was established that depending on the relative concentrations of HTTA and
TOPO, a number of species with the composition M(TTA)a(ClO4)4-a·b TOPO, with a ranging from 1 to 4 and b having values of 1 or 2, are involved in the extraction. Several equilibrium constant
values are given.
Authors:S. Patil, V. Ramakrishna, M. Sajun, and R. Thiagarajan
Synergistic extraction of Th(IV) from perchlorate medium by mixtures of HTTA and TBP was studied. These studies include the
effect of the ionic strength, temperature and the diluents on the extraction. Ionic strength was found to influence the extraction
of Th(TTA)4 and Th(TTA)4·TBP whereas the adduct formation in the organic phase was almost unaffected. Increase of temperature resulted in a decrease
of the extraction of Th(IV). The stability of the adduct was found to decrease in the order, cyclohexane > benzene > chloroform.