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A YPO4:Er3+–Yb3+ nanophosphor has been synthesized by a facile coprecipitation method. The photon upconversion has been carried out at 980 nm continuous-wave laser diode excitation. Optical heating...

Present study reports simultaneous batch and column extraction of Pu(IV) and Am(III) followed by selective stripping from actual analytical waste solution generated during quality control operations. N, N, N′, N′ tetra(2-ethylhexyl) diglycolamide (TEHDGA), di(2-ethylhexyl) phosphoric acid (DEHPA), individually and their combination, encapsulated in polyether sulphone resin beads have been investigated. TEHDGA + DEHPA encapsulated resin showed better performance with respect to kinetics (2 h) and extent of extraction (KD ~ 8000 at 5 M nitric acid) for both Am(III) and Pu(IV). Interesting presence of DEHPA, inefficient as extractant at high nitric acid molarity, improved polymer extraction characteristics. Extraction selectivity over assorted metal ions and reusability for three cycles of operations was established.

Hollow fibre membrane (HFM) operation in supported liquid membrane mode has been successfully employed for the separation of terbium from lean aqueous media by using EHEHPA (PC88A) as an extractant...

Hollow Fibre Membrane (HFM) operation in non-dispersive solvent extraction (NDSX) mode has been successfully employed for the separation of dysprosium from NdFeB magnetic scrap material using EHEHPA as an extractant. Effect of various hydrodynamic parameters including aqueous phase acidity, extractant concentration, Dy concentration in feed, phase ratio and flow rate were investigated to optimize the condition for quantitative recovery of dysprosium from the leach liquor obtained by the dissolution of hard disk drive (HDD) in nitric acid media. 0.5 M EHEHPA, 0.3 M HNO3 as aqueous feed phase, 100 ml/min flow rate and phase ratio of 1:1 were found to be optimum for both the cycle test runs. Taking the advantage of fast extraction kinetics of dysprosium, two cycle HFM-NDSX approach was adopted to concentrate Dy from 20 to 83% in first cycle while raising its purity >97% in the second cycle. The overall process also yielded neodymium rich by-product for its further purification.

Separation and purification of rare earth elements (REEs) from each other has been a challenging task and a topic of immense interest across the world. The separation of high purity yttrium from chemically similar heavy rare earths (HREs) could be possible due to its differential behavior in thiocyanate & nitrate media with quaternary amine type of extractant Aliquat336. In case of a hard donor like nitrate ion, Y behaves like heavy rare earths (HERs), more or less in accordance with its ionic radii. On the contrary, in thiocyanate medium, the extraction properties of Y follows the light rare earths (LREs) which makes its separation from Er and other HREs effective. In the present investigation, a microscopic analysis employing computational tools has been utilized to offer an explanation for this curious behaviour of yttrium. The computational results bring out the striking fact that while the behavior of Y remains unchanged in two mediums, it is the trend within the lanthanide series that changes between the two mediums. It is observed that the size of the REE nitrates follow a decreasing trend along the lanthanide series, where Y nitrate shows comparable bond lengths with Er nitrate. On the other hand REE thiocyanates follow an increasing trend in size, where Y thiocyanate bond lengths are closer to the La thiocyanate. Similar trend is observed for the partial charges on the outer atoms of REE nitrates and thiocyanates, which affects the electrostatic binding interaction with the extractant Aliquat336. The contrasting trend among the lanthanide series is further explained in terms of spin density analysis shows that, in case of a hard donor like nitrate, f-electron delocalization takes place into the ligand and the size of the REE nitrates follow the lanthanide contraction. Y in this case behaves like HREs. On the contrary, in thiocyanate medium there is no delocalization of f-orbital in inner-sphere thiocyanate complex and due to absence of f orbital in Y, it occupies position with light rare earths as extraction follows the trend of electrostatic attraction between cation and ligand. Understanding of this extractant interaction is expected to provide a knowledge based approach for the development of new extractant molecules with better binding capacity for specific REE of interest.

Polyethersulfone (PES)-based beads encapsulating organic extractant PC88A and additives have been prepared, characterized and evaluated for yttrium sorption from aqueous chloride medium. The role of additives on modifying the morphological structure of the beads resulting in varying degrees of sorption has been examined. Amongst the various additives investigated, polyvinyl alcohol (PVA) led to significantly enhanced sorption of yttrium. The sorption data were analyzed by different isotherms. The mechanism of sorption was found to proceed via intraparticle diffusion as well as film diffusion following pseudo-second-order kinetics and chemisorption. The polymeric beads were found to be highly stable toward repeated numbers of sorption and desorption of yttrium.

Polyethersulfone-based beads encapsulating di-2-ethylhexyl phosphoric acid have been synthesized and evaluated for the recovery of rare earth values from the aqueous media. Percentage recovery and the sorption behavior of Dy(III) have been investigated under wide range of experimental parameters using these beads. Taguchi method utilizing L-18 orthogonal array has been adopted to identify the most influential process parameters responsible for higher degree of recovery with enhanced sorption of Dy(III) from chloride medium. Analysis of variance indicated that the feed concentration of Dy(III) is the most influential factor for equilibrium sorption capacity, whereas aqueous phase acidity influences the percentage recovery most. The presence of polyvinyl alcohol and multiwalled carbon nanotube modified the internal structure of the composite beads and resulted in uniform distribution of organic extractant inside polymeric matrix. The experiment performed under optimum process conditions as predicted by Taguchi method resulted in enhanced Dy(III) recovery and sorption capacity by polymeric beads with minimum standard deviation.

An environment benign process for the separation of rare earths has been delineated for the first time by developing polyethersulfone based composite beads through phase inversion method, where the use of hazardous organic diluents could be circumvented. The porosity and pore structure of these beads were controlled through different additives, of which, polyvinyl alcohol and multiwall carbon nanotubes proved to be the most efficacious. The extraction efficiency of rare earths was ameliorated by four fold with the application of the developed nanotube incorporated beads. The influence of various process parameters, namely, aqueous phase acidity, metal ion concentration, presence of other competitive ions and temperature on the separation of representative yttrium ion has been elaborated in the present investigation. The experimental results attribute to the excellent stability and reusability of the developed beads. The feasibility of employing this novel technology in large scale has been established by successful operation in continuous column mode. The developed assay exhibits profound application towards a greener approach due to the elimination of hazardous organic diluents and prevention of significant organic extractant loss during the process of recovery of rare earths from aqueous media.

Extractant impregnated polyethersulfone beads have been prepared by phase inversion method and investigated for yttrium recovery from aqueous medium. The effect of experimental parameters on yttrium sorption has been studied. Quantitative sorption of yttrium (> 90%) was attained after 8 hours of equilibration time in the case of D2EHPA impregnated composite beads. Analysis of sorption data by different kinetic and diffusion models suggested that the sorption of Y(III) followed the pseudo-second order model. Stability tests with polymeric composite beads by multiple cycles of sorption and desorption of Y(III) have established the feasibility of reusing the beads for sorption of metal ions.

According to a relatively recent UNICEF report, 15 percent of the infant population of the world is of low birth weight with India accounting for one third of all the world's low-weight newborns. Twenty percent of all low birth weight infants die within a month. This mortality figure is higher in developing countries due to inadequate nutritional intake by pregnant women. Development of a new package of nutrient-rich food based on egg or milk or soy bean proteins, containing multiple micronutrient supplements, available at affordable cost, may protect against morbidity and mortality among pregnant women as well as low birth weight in newborns. These benefits may continue to decrease morbidity and mortality during infancy and childhood and might reduce the risk of chronic diseases in later adult life.

The separation of entrained di-nonyl phenyl phosphoric acid (DNPPA) from merchant grade phosphoric acid (MGA) by adsorption on the coconut shell based activated charcoal has been carried out. The effect of various process parameters, such as DNPPA concentration in aqueous phase of MGA, equilibrium time, amount of activated charcoal and temperature upon adsorption capacity of activated charcoal has been studied. The results showed that the adsorption equilibrium was reached after 240 minutes. The adsorption phenomenon followed pseudo-second order kinetics. Adsorption of DNPPA increased with initial concentration of DNPPA in the range of 50 to 200 mg/L. The experimental data fitted well with the Freundlich isotherm model. Decrease in adsorption with increase in temperature suggests that the adsorption process is exothermic in nature. The value of enthalpy change (ΔH = −35.52 kJ/mol) indicated that DNPPA adsorption on activated charcoal is a physisorption phenomenon. Column operation was carried out to obtai...

The present paper deals with the study on phase separation kinetics of di nonyl phenyl phosphoric acid (DNPPA)–tri octyl phosphine oxide (TOPO)–petrofin–phosphoric acid system. Factorial design of experiment (DOE) has been utilized to illustrate the effect of different process variables such as extractant concentration in the organic phase, phosphoric acid concentration in the aqueous phase, temperature, phase ratio, and stirring speed on phase separation time (tp) and specific settling rates (SSR of organic and aqueous phase). The dependence of individual variables and their mutual interactions on phase separation kinetics was also deduced. A mathematical correlation relating process variables and response (tp and SSR) was developed which allows defining the percent effect of each of the variables on response. The influence of variables on response was found to be significant at 99% confidence level, while the interaction effect among variables aqueous acid concentration, organic concentration, and tempe...

Polyethersulfone beads containing D2EHPA as extractant have been prepared by phase inversion method and characterized by optical microscope, SEM and TG-DTA. Subsequently these beads were tested for their suitability for separation of rare earths from various aqueous media. Except nitrate medium, the extraction of rare earths was found to be comparable in perchlorate, chloride and sulfate medium. Effect of aqueous acidity, metal ion concentration in aqueous feed, concentration of organic extractant inside the beads, extractant to polymer ratio, liquid to solid (L/S) ratio, additive concentration, and temperature on the extraction of rare earths was studied. Increase in acidity, L/S ratio, metal ion concentration and polymer to extractant ratio led to decrease in extraction of rare earths. Increase in extractant concentration inside the bead resulted in enhanced extraction of metal ion. Extraction of rare earths increased in the range of 30–50 °C and thereafter showed a decreasing trend in between 50 and 70 °C. Stripping of rare earth from composite beads was found to be effective (>90%) with 40% HCl and 30% H 2 SO 4.

In the present study an attempt has been made to understand the extraction and stripping behavior of iron (III) with D2EHPA alone and its mixture with TBP or TOPO in phosphoric acid medium. Effect of variables such as concentrations of iron (III), phosphoric acid, and phosphate in the aqueous phase, D2EHPA, TBP, and TOPO concentrations in the organic phase and temperature on the extraction process has been studied. The extraction of iron (III) decreased with increase in phosphoric acid concentration. The increase in D2EHPA concentration increased the extraction of iron (III). The presence of TOPO or TBP with D2EHPA showed antagonism. The increase in temperature decreased the extraction of iron (III) with D2EHPA alone and its mixture with either TOPO or TBP showing the exothermic nature of the extraction reaction. The stripping of iron (III) by various reagents followed the order: oxalic acid > phosphoric acid > hydrochloric acid > sulphuric acid > mixture of sulphuric and hydrofluoric acids > ascorbic aci...

A method to simultaneously recover yttrium and uranium from phosphoric acid using DNPPA + TOPO and D2EHPA + TBP solvent systems has been developed. The solvent mixture DNPPA + TOPO is employed for merchant grade phosphoric acid, while the D2EHPA + TBP solvent system is employed for wet process phosphoric acid to recover uranium and yttrium. In the method, four steps are involved for the yttrium recovery: (1) yttrium is co-extracted with uranium using the two organic systems; (2) yttrium is selectively stripped from the loaded organic solutions; (3) yttrium is recovered from the strip liquor by double sulphate salt precipitation; (4) yttrium double sulphate salt is dissolved and precipitated with oxalic acid to generate pure yttrium product. Selective stripping of yttrium from the loaded organic solutions with various strip solutions was tested. It was found that 10% (w/v) Na2SO4 + 30% H2SO4 and H2SO4 (30 to 40%) are the most preferable conditions with more than 95% of yttrium recovered and less t...

The phase separation kinetics for the process of recovering uranium from phosphoric acid medium (WPA) with 1.5 M D2EHPA + 0.2 M TBP is influenced by process variables such as D2EHPA/TBP concentration in the organic phase, acid concentration of the aqueous phase, temperature, phase ratio (A/O). To correlate the effect of these variables on phase separation kinetics (phase separation time, specific settling rate (SSR) for aqueous and organic), a statistical approach of data generation and analysis using factorial design of experimentation (DOE) has been adopted. The significance of individual variables and their mutual interactions on phase separation behaviour in WPA-D2EHPA + TBP process was statistically derived using the DOE data. Mathematical models representing a relation between the responses (phase separation time, SSR organic or SSR aqueous) and variables were established. The percentage effects of each variable on response were calculated from these models. Further a real variable mathemat...

Kinetics of the mass transfer processes involved in uranium recovery from wet process phosphoric acid (WPA) by solvent extraction employing synergistic extractants has been studied. In the present investigation results on the kinetics of separation of entrained solvent by diluent washing and uranium mass transfer behaviour have been discussed. Kinetic studies for the entrained solvent separation by diluent (petrofin) wash for D2EHPA/WPA system showed significant dependence of the rate constant value on the variables such as phase ratio, temperature and agitator speed. Kinetic studies on the mass transfer of U(VI) from phosphoric acid with 1.5 M D2EHPA+ 0.2 M TBP have been carried out using a constant interfacial area cell (Lewis cell). The effect of stirring speed, interfacial area, acidity of aqueous phase, extractant concentration in organic phase and temperature on the extraction rate constant indicate that both chemical reaction and diffusion, control the rate of uranium extraction from phosphoric aci...

Time resolved fluorescence spectroscopy (TRFS) of Eu(III) (an analogue of trivalent actinides) complexation with humic acid (HA) and its model compounds, namely phthalic acid (PA), mandelic acid (MA) and succinic acid (SA) has been carried out at varying concentration ratios of ligand to metal ion. The emission spectra were recorded in the range of 550–650 nm by exciting at an appropriate wavelength. The intensity of the 616 nm peak of Eu(III) was found to be sensitive to complexation. The ratio of the intensities of 616 and 592 nm peaks was used to determine the stability constants of Eu-phthalate, Eu-mandelate and Eu-succinate complexes. In the case of model compounds, the life-time was found to increase with increasing ligand to metal ratio (L/M) indicating the decrease in quenching of the fluorescence by coordinated water molecules with increasing complexation. On the other hand in the case of HA, the life-time was found to be constant at least up to L/M of 5, indicating the formation of outer sphere complex. Beyond L/M = 5 the life-time value was found to increase which can be attributed to the binding of the metal ion to the higher affinity sites in the HA macromolecule.