Carrier Distillation Technique Research Articles

Development of Methodologies for the Chemical Quality Control of Zircon, A Precursor for Zirconium Production

AbstractMethodologies have been developed for the chemical quality control of zircon mineral by EDXRF and D.C.Arc carrier distillation technique. EDXRF technique was found to be preferred for major and minor constituents including non‐metal analytes, while D.C.Arc carrier distillation OES was found to be good for minor and trace metallic constituents including low Z elements. A comparative evaluation of the analytical performance (detection limit, sensitivity, precision, linear dynamic range) was performed. A multipoint standardization was carried out using the base material of 1 : 1 SiO2 : ZrO2 powder mixture to establish calibration curves for the analytes after identification of interference free and the best performed emission and X‐ray analytical lines. In zircon sample, Si, Zr and Y were found to be present as major constituent, with Ga, Ca, Ru, Rh, Fe, Mn, Mg, I, S as minor and Zn, Cr, Sn, Li as trace constituents. The total uncertainty of the EDXRF measurements was evaluated. The statistical t‐test analysis was carried out for 10 degrees of freedom with 95 % confidence interval. The experimentally obtained t‐values were found to be lower compared to the corresponding tcri value revealing the reliability of the measurements. Elemental distributions of the analytes were also investigated using five different zircon samples.

Determination of analytes at trace level in uranium matrix by ICP-AES without chemical/physical separation

Determination of trace metallic constituents in nuclear materials e.g. U, Pu, Am, Zr etc. by Atomic Emission Spectroscopy requires the separation of the major matrix without the loss of analytes at trace level. For DC Arc carrier distillation technique, carrier is used to separate the matrix physically according to the volatility of the analytes while appropriate extractant in suitable diluent is used for chemical separation in inductively coupled plasma atomic emission spectroscopy (ICP-AES). In the present study an attempt was made to develop a methodology for the determination of B, Cd, Mg, Zn, Al, Sr and Sc at trace level (up to 0.1 μg/mL) in uranium matrix without any chemical or physical separation. It involves identification of suitable analytical lines of uranium for its ICP-AES determination; study the spectral interference of uranium to choose interference free analytical lines, optimization of instrumental and experimental parameters etc. The method was validated using synthetic samples.

Glycerol production by microbial fermentation: A review

Microbial production of glycerol has been known for 150 years, and glycerol was produced commercially during World War I. Glycerol production by microbial synthesis subsequently declined since it was unable to compete with chemical synthesis from petrochemical feedstocks due to the low glycerol yields and the difficulty with extraction and purification of glycerol from broth. As the cost of propylene has increased and its availability has decreased especially in developing countries and as glycerol has become an attractive feedstock for production of various chemicals, glycerol production by fermentation has become more attractive as an alternative route. Substantial overproduction of glycerol by yeast from monosaccharides can be obtained by: (1) forming a complex between acetaldehyde and bisulfite ions thereby retarding ethanol production and restoring the redox balance through glycerol synthesis; (2) growing yeast cultures at pH values near 7 or above; or (3) using osmotolerant yeasts. In recent years, significant improvements have been made in the glycerol production using osmotolerant yeasts on a commercial scale in China. The most outstanding achievements include: (1) isolation of novel osmotolerant yeast strains producing up to 130 g/L glycerol with yields up to 63% and the productivities up to 32 g/(L day); (2) glycerol yields, productivities and concentrations in broth up to 58%, 30 g/(L day) and 110–120 g/L, respectively, in an optimized aerobic fermentation process have been attained on a commercial scale; and (3) a carrier distillation technique with a glycerol distillation efficiency greater than 90% has been developed. As glycerol metabolism has become better understood in yeasts, opportunities will arise to construct novel glycerol overproducing microorganisms by metabolic engineering.

Trace Metal Assay of Uranium Silicide Fuel

A comprehensive trace metal assay of uranium silicide, a fuel for nuclear research reactors that employs low-enrichment uranium, is carried out by atomic spectrometry. Of the list of specification elements, 21 metallic elements are determined by a direct current (dc) arc carrier distillation technique; the rare earths yttrium and zirconium are chemically separated from the major matrix followed by a dc arc/inductively coupled argon plasma (ICP) excitation technique in atomic emission spectrometry (AES); silver is determined by electrothermal atomization-atomic absorption spectrometry (ETA-AAS) without prior chemical separation of the major matrix. Gamma radioactive tracers are used to check the recovery of rare earths during the chemical separation procedure. The detection limits for trace metallics vary in the 0.1- to 40-ppm range. The precision of the determinations as evaluated from the analysis of the synthetic sample with intermediate range analyte concentration is better than 25% relative standard deviation (RSD) for most of the elements employing dc arc-AES, while that for silver determination by ETS-AAS is 10% RSD. The precision of the determinations for four crucially important rare earths by ICP-AES is better than 3% RSD.

Trace metal assay of thorium oxide by atomic emission spectrometry

An Atomic Emission Spectrometric (AES) method has been developed for the direct determination of twenty-two metallic elements at trace concentrations in thorium oxide. The method is based on the use of a d.c. arc — carrier distillation technique with 12% composition of a mixed carrier, viz. AgCl+SrF2 in 5:1 proportion, and is equally applicable to both volatile and refractory analytes. A direct reading emission spectrometer with computerised data acquisition and processing facility has been used in these studies. The standardisation procedure includes study of volatilisation/excitation characteristics of the analyte elements to optimise choice and proportion of the carrier and signal integration time apart from optimisation of other experimental parameters such as arc current, viewing position of the arc plasma, sample charge etc. The detection limits for the analytes lie in the range 0.1–50 ppm while the precision of determinations is better than 15% for most of the elements as evaluated from the repetitive analyses of spiked samples.

Emission spectrographic determination of volatile trace elements in geologic materials by a carrier distillation technique

Trace levels of chalcophile elements that form volatile sulfide minerals are determined in stream sediments and in the nonmagnetic fraction of a heavy-mineral concentrate of stream sediments by a carrier distillation emission spectrographic method. Photographically recorded spectra of samples are visually compared with those of synthetic standards for the two sample types. Rock and soil samples may also be analyzed by comparison with the stream-sediment standards. A gallium oxide spectrochemical carrier/buffer enhances the early emission of the volatile elements. Detection limits in parts per million attained are: Sb 5, As 20, Bi 0.1, Cd 1, Cu 1, Pb 2, Ag 0.1, Zn 2, and Sn 0.1. A comparison with other methods of analysis, total-burn emission and atomic absorption spectroscopy, shows good correlation for standard reference for materials and samples from a variety of geologic terranes.

Spectrographic analysis of high-purity calcium oxide by a carrier distillation technique

Spectrographic analysis of high-purity calcium oxide by a carrier distillation technique

Carrier distillation-ICAP approach for trace metal assay of U3O8 powder

A new approach for the trace metal assay of U3O8 powder has been described. The carrier distillation technique used for selective volatilization of trace metals in U3O8 with d.c. arc excitation is adapted for the release of analytes from the solid sample into the ICAP source by inductively heating the sample. The experimental parameters have been optimised for the direct determination of Cd, Cu, K, Na, Ni and Pb. The performance of the method developed here is tested for the precision and accuracy of determinations by analysing spiked U3O8 samples and NBL U3O8 reference standards (standard deviation 2–9%). The method appears promising to be developed as a highly precise analytical optical emission spectrometric method as it adds to the ingenuity of the carrier distillation method, the advantages of ICAP.

Determination of non-rare earth impurities in purified Dy2O3— A spectrographic method using carrier distillation technique

A d. c. arc Spectrographic method employing the carrier distillation technique has been developed for the determination of the non-rare earth impurities Bi, Cu, Fe, Mg, Mn, Ni, Pb and Sn in Dy2O3 in the range of 1–100 ppm. The sample is ground with 5% AgCl containing 1000 ppm of Ge as internal standard. The average precision of the method in terms of the coefficient of variation of the concentration is 12–15% for the different impurities.

A New Carrier for Direct Spectrographic Determination of Trace Alkalies and Alkaline Earths in High Purity Thorium Oxide

Abstract A d.c. arc emission spectrographic method is described for the determination of sub ppm levels of Ba, Li and Sr and ppm levels of Cs, K and Na in high purity thorium oxide. The method which employs RbCl as carrier is simple and rapid and does not involve the use of any special atmosphere for exciting the sample. It was observed that RbCl shows definite improvement over AgCl in carrier action. The carrier distillation technique reported makes possible the following range of estimations: Li: 0.02 – 5.0 ppm, Ba, Sr: 0.5 – 20 ppm, Cs: 2–50 ppm, K,Na: 5–100 ppm. The detection limit obtained by this method for Li and Sr is lower than that obtained by the earlier carrier-distillation methods reported as well as other direct sensitive techniques of Zeidel and Avni for the analysis of Tho2. The precision of the method ranges from 8% for Cs to 17% for Ba. Volatilization studies on the choice of carrier material are presented.

Direct Spectrographic Determination of In, La, Nb and Sr in Thorium Oxide

Abstract A d.c. are emission spectrographic method is described for the determination of ppm levels of In, La, Nb and Sr in thorium oxide. The method permits determination of the above low and high volatile impurity elements in thoria using AgCl as carrier in an atmosphere of oxygen. The carrier-distillation technique reported makes possible the following range of estimations: In : 1–50 ppm; La, Nb : 10–500 ppm and Sr: 2–100 ppm. The method is simple and rapid and its precision ranges from 14% for In to 18% for Nb. Observations made on the choice of carrier and internal standard are presented.

Spectrographic determination of metallic impurities in PuO2

An emission spectrographic method has been developed for the estimation of 22 metallic impurities in plutonium dioxide using carrier-distillation technique Silver chloride at 5% concentration in a charge of 100 mg has been used as the carrier. Mixed oxide standards containing 10% PuO2 have been used for the analysis of matching composition of plutonium samples. Precision and accuracy determinations of the synthetic samples indicate 7–16% deviation for most of the elements. The work described includes analysis of reference samples and matrix effect studies. The method is suitable for the chemical quality control analysis of plutonium oxide to be used for Fast Breeder Test Reactor (FBTR) fuel.

Carrier Distillation Method for the Determination of Impurities in Niobium Oxide

A carrier distillation technique is described for the analysis of trace impurities in niobium oxide. The carrier used is a 1: 1 mixture of AgCl and AgF. Separation of the carrier and sample charge along with the use of a boiler cap on the electrode cup greatly reduces the background and yet allows the impurities to be distilled into the arc within 90 sec. Sensitivity and precision data are included for 13 impurity elements.

Spectrographic Determination of Trace Lithium in Some Refractory Oxides by a Hollow-Cathode Discharge Tube

The use of uranium, thorium, zirconium, and aluminum in nuclear technology requires, among other things, the development of analytical methods for the determination of low concentrations of elements having a large cross section. This group of elements also includes lithium (71.0 b), so its determination in some cases is indispensable. In the field of flame photometry and emission spectrography several papers have been published on the determination of lithium in these materials. Perman described a flame photometric method for the determination of lithium in uranium which does not require separation. The carrier-distillation technique has been used to determine lithium in uranium, zirconium, thorium, and aluminum. Using the chemical preconcentrations and the copper spark technique, lithium has been determined in uranium and thorium. The high-tension arc, the hollow-cathode discharge tube, and the evaporation–distillation method has been successfully applied to the analysis of zirconium.

Direct Spectrometric Determination of Dy, Eu, Gd, and Sm in High-Purity Thorium Dioxide

A spectrometric method is described for the direct determination of Dy, Eu, Gd, and Sm in the parts-per-million range in thorium dioxide. The method, based upon a carrier-distillation technique, utilizes silver chloride as a carrier and neodymium as an internal standard. Direct-current arc excitation in an atmosphere of 80% argon–20% oxygen prevents formation of cyanogen band spectra and thereby permits the use of sensitive lines in the regions normally obscured by cyanogen bands. The method fulfills the requirements of precision and sensitivity for specification analysis of reactor-grade thorium dioxide with a time saving of approximately 60%, as compared to conventional methods involving chemical separation.

Simultaneous Determination of Calcium, Lithium, and Potassium in High-Purity Thorium Dioxide

In the determination of calcium, lithium, and potassium in a refractory matrix such as thorium dioxide, the task can be accomplished using a carrier distillation technique with gallium oxide or silver chloride as the carrier. Complications arise, however, if low concentrations require the use of the most sensitive analytical lines of each: e.g., Ca 3933.67, Li 6707.84, and K 7664.91. The resultant need for broad wavelength coverage at highest sensitivity would require two or three separate exposure conditions with three different photographic plate emulsions. Ideally, Ca 3933.67 A would require an SA-1 emulsion; Li 6707.84 A would require a II-F, usually with a filter to remove scattered light; and K 7664.91 A would require a 1-N with a filter (Corning Glass 3484) mounted in front of the slit to remove interfering second-order cyanogen bands.

Direct determination of small quantities of rare earth and yttrium oxides in thoria by emission spectroscopy

Methods are proposed for the determination of submicrogram quantities of rare earth and yttrium oxides in thorium oxide by emission spectroscopy, without previous separation or concentration of these oxides in the sample. It is possible to volatilise these refractory materials from the thoria using silver chloride as the carrier. The carrier distillation technique in conjunction with relatively high dispersion spectroscopy (0.8–1.1 Å/mm) makes possible analyses at levels which were previously only feasible by preconcentration methods (e.g., La 2O 3 and Y 2O 3, 5 ppm; Nd 2O 3 and Sm 2O 3 10 ppm; CeO 2 and Pr 6O 11, 20 ppm in a 10-mg sample of ThO 2).

Spectrographic Analysis of Tantalum and Tantalum Oxide

Tantalum metal is analyzed for 12 impurity elements by using a carrier distillation technique with a dc arc. The metal is oxidized in a muffle oven at 900°C. The oxide is mixed with a special carrier made of silver metal, silver chloride, and barium fluoride. A set of standards is included on each plate, and the analytical curves are linear for the concentration range used. The coefficient of variation varies from 30 to 87%

Spectrographic Analysis of Hafnium by a Point-to-Plane Technique

A method has been developed for the analysis of hafnium metal for aluminum, copper, iron, titanium, and tungsten in the ppm range and zirconium in the 1 0–4.0% range. Solid machined pieces 1 × 1 in. or larger are used. Spectra are excited with a low voltage ignited ac arc with low inductance and capacitance. Hafnium serves as the internal standard The method offers an increase in speed and improved precision over the carrier distillation technique which has been commonly used