K. K. Swain

Sorption of As(III) and As(V) on chemically synthesized manganese dioxide

Sorption of As(III) and As(V) on manganese dioxide was studied by batch equilibration method using 76As radioactive tracer. Manganese dioxide was prepared by two different methods viz. reacting (a) KMnO4 solution with MnSO4 solution, and (b) KMnO4 solution with concentrated hydrochloric acid. Manganese dioxide was characterized by zeta potential measurement, surface area measurement, thermogravimetry (TG), differential thermal analysis (DTA) and X-ray diffraction (XRD) techniques. Point of zero charge (PZC) for manganese dioxide was between pH 3 and 4. Radioactive tracer (76As) was prepared by neutron irradiation of arsenious oxide in self serve facility of CIRUS reactor followed by conversion to As(III) and As(V), by appropriate chemical methods. Sorption of As(III) and As(V) were studied separately, between pH 1 to 11, using (i) freshly prepared, (ii) air-dried and (iii) aged manganese dioxide. Sorption of As(III) and As(V) on freshly prepared as well as aged manganese dioxide, from both the methods was greater than 98% between pH 1 to 9 and decreased above pH 9. Percentage sorption was comparable for manganese dioxide prepared by both the methods in different batches. Sorption capacity was ∼2 mg g−1 for both As(III) and As(V). Arsenic was desorbed from the manganese dioxide by 0.1 M sodium hydroxide and oxidation state of desorbed arsenic was determined by solvent extraction method. It was found that the desorbed arsenic was present in As(V) oxidation state, independent of the initial oxidation states. This simple and direct chemical evidence, establishing that As(III) is converted to As(V) by manganese dioxide, is reported for the first time. Sorption of As(III) and As(V) on manganese dioxide did not cause an increase in manganese concentration above solubility limit confirming that Mn2+, formed during oxidation of As(III) to As(V), was re-adsorbed.

Evaluation of uncertainty in the energy dispersive X-ray fluorescence determination of platinum in alumina

Evaluation of uncertainty in the Energy Dispersive X-ray Fluorescence (EDXRF) spectrometric determination of platinum in alumina catalysts is discussed. Pressed pellets of the platinum standard and a catalyst sample were prepared by using microcrystalline cellulose powder as the base material. A linear calibration of the X-ray fluorescence spectrometer was obtained in the range of 0.1–3 mg g−1 of platinum using pellets of matrix matched synthetic standards. The calibration function was obtained through bivariate least squares fitting, in conjunction with weighted regression of the residuals. The EDXRF results were compared with those obtained by instrumental neutron activation analysis and inductively coupled plasma optical emission spectrometry. Analysis of variance established the statistical parity of the results obtained by all the three techniques. A comprehensive evaluation of the various sources of uncertainty in the complete measurement process was carried out using a bottom-up approach. The main source of uncertainty was identified as the calibration of the EDXRF spectrometer, in which the major share was attributed to the intercept of the calibration function.

Preconcentration and determination of mercury in high purity arsenic

Abstract An analytical procedure for the determination of trace amounts of mercury in high purity arsenic metal/oxide, widely used in electronic devices, is presented in this manuscript. Pre-concentration of mercury from a large amount of the matrix on a small amount of anion exchanger in hydrochloric acid medium was used to enrich the analyte concentration, followed by its determination using neutron activation analysis (NAA). A detailed study was carried out for the quantitative separation of the analyte from the matrix along with the precautions to be considered for the accurate determination of this volatile element. The separation of the analyte was quantitative and the validity of the procedure was confirmed by tracer studies, standard addition of the analyte to the matrix and by analyzing high purity arsenic for which certified values are available. The overall reproducibility of the separation procedure was 2–10%.

Comparison and statistical evaluation of neutron activation methodologies for the determination of gold in copper concentrate

Gold was determined in copper concentrate by an instrumental neutron activation analysis technique using the relative method. The determination was repeated by radiochemical and chemical neutron activation analysis with the aid of an anion exchange strategy for the chemical separation of gold from the matrix (Fe, Cu, and Zn). Irradiation of copper concentrate samples was carried out in APSARA reactor (BARC, India) with a thermal neutron flux of about 1012 cm−2 s−1. Analysis of variance established that the results obtained by instrumental, radiochemical and chemical methodologies were statistically indistinguishable. Among the three approaches, radiochemical activation showed superior detection limits, which was attributed to both the reduction in background and increase in sensitivity. The best measurement repeatability was observed in chemical activation methodology, compared to the other two. The rationale behind the improvement in measurement repeatability was the capability of chemical activation to process a larger mass of sample for each replicate, which resulted in improved counting statistics and reduction in sampling error with respect to gold. Combined uncertainty for all the three methodologies was evaluated through the bottom-up approach. Systematic evaluation of various uncertainty parameters showed that the major contributor to the combined standard uncertainty was the counting statistics during the instrumental approach and the chemical separation yield during radiochemical and chemical activation. The combined uncertainty for all the three approaches was less than the measurement repeatability indicating the inhomogeneous distribution of gold in copper concentrate. Calculations showed that the sampling constant for gold in copper concentrate was about 22 g.

High purity scandium and ion-exchangers: Application in neutron activation analysis

This manuscript presents a typical analytical application of ion-exchange resins in mixed solvent media for the separation and determination of a number of trace elements in high purity scandium, where direct instrumental approach for its characterization/analysis is difficult. This work demonstrated, how a few beads of ion exchange resin could be effectively used for the pre-concentration of the separated trace elements for their determination using neutron activation analysis (NAA). Radiotracer and standard addition methods were used for validation.

Sorption of arsenic on manganese dioxide synthesized by solid state reaction

Arsenic in groundwater is a major concern in many parts of the world and suitable sorbents are required for removal of arsenic from ground water. Removal of arsenic from groundwater has been studied using manganese dioxide, synthesized by solid state reaction of manganese acetate with potassium permanganate. Manganese dioxide was characterized by X-ray diffraction (XRD), zeta potential, surface area, particle size measurements and thermal analysis. XRD measurement showed that the manganese dioxide had α-MnO2 structure. Sorption of As(III) and As(V) on manganese dioxide was studied by radiotracer technique using 76As radio isotope. Arsenic removal efficiency for both As(III) and As(V) at concentration of 2 mg L−1 was ∼99% in the pH range of 3–9. The sorption capacities for As(III) and As(V) were ∼60 mg g−1. Kinetic studies showed that the equilibrium was reached within 30 s. Arsenic sorbed on manganese dioxide was present as As(V) irrespective of initial oxidation state. The presence of Ca2+, Mg2+, Cl− and SO42− up to a concentration of 1000 mg L−1 had no significant effect on arsenic sorption. The sorption of arsenic decreased significantly in the presence of phosphate and bicarbonate anions above 10 mg L−1. Arsenic sorbed on manganese dioxide was desorbed by 0.1M NaOH. Arsenic was effectively removed by manganese dioxide from groundwater samples collected from arsenic contaminated areas of West Bengal, India.

Studies of kidney stones using INAA, EDXRF and XRD techniques

Four kidney stones collected from patients being treated in the Advance Urology Centre of PGIMR, Chandigarh were characterized using instrumental neutron activation analysis (INAA), energy dispersive X-ray fluorescence (EDXRF) and X-ray diffraction (XRD) techniques. For INAA, samples were irradiated in tray rod facility of Dhruva reactor, Mumbai and pneumatic fast transfer system of KAMINI reactor, IGCAR, Kalpakkam. Radioactive assay was carried out using HPGe detector coupled to 8k channel analyzer. Elements determined in the samples by INAA are Zn, Sr, Co, Fe, Cr, Sc, Se, Na and Mn. EDXRF was used for the quantification of Ca. XRD patterns showed that three of the kidney stones are calcium oxalate stone and the other one is uric acid stone. The concentrations of trace elements in general were found to be higher in calcium oxalate stones and positive correlation was observed in the concentrations of Ca with Sr and Zn.

Grass to cow milk transfer coefficient (Fm ) of Iodine for equilibrium and emergency situations

Radioiodine ( 131 I) is one of the radionuclides likely to get released into the atmosphere in case of a reactor accident, though chances of such an accident are very remote due to stringent engineering safety features. If released to the environment during an accident, 131 I may enter the grass→cow→cow milk pathway, leading to increased thyroid dose to those consuming milk, especially infants and children. The estimation of site-specific grass to milk transfer coefficient (F m ) for iodine is essential for an accurate assessment of the radiological hazard to the population in the region surrounding a nuclear power plant. In this study, a method based on the chemical separation of iodine present in grass and cow milk, and subsequent neutron activation analysis (NAA) has been optimized for the determination of stable iodine concentration in grass and cow milk. The method involves preconcentration of iodine from the sample matrix, and determination of iodine by NAA. The detection limit of stable iodine in milk was found to be 1 ng/mL. For the validation of the result, iodine concentration in NIST reference materials was determined simultaneously. The present study has yielded a F m value of 5.6 × 10−3 d/L for dairy farm cows and 6.3 × 10−3 d/L for local breed cows under equilibrium conditions. These results are similar to the values given in International Atomic Energy Agency report (TRS-472). To simulate a rapid deposition of iodine on grass and for the estimation of F m value for an emergency situation, grass grown in the experimental field was sprayed with stable potassium iodide solution and fed to the adopted cows, and the milk samples were collected regularly and analyzed. The F m value for the simulated accidental situation was found to be 3.9 × 10−3 d/L.

Determination of impurities in graphite using synchrotron radiation based X-ray fluorescence spectrometry

Determination of impurities namely Ca, Mn, Fe, Ni, Zn, Sr and Pb in graphite by energy dispersive X-ray fluorescence spectrometry is described using microfocused synchrotron radiation. The internal standard and standard addition methodologies were adopted for quantification and the results were compared with tube-based X-ray fluorescence spectrometry. Analysis of the results by the F and t-tests revealed their statistical equivalence. Synchrotron measurements improved the detection limits by an order of magnitude compared to the tube based technique. Cr and Zr, which were below the quantification limit in tube based technique, were also quantified by synchrotron based technique.

Determination of leachable arsenic from glass ampoules

Appreciable amounts of different arsenic compounds are used in the manufacture of glass and glass ampoules (injection vials and bottles) used to store drugs. Exposure/intake of arsenic to human beings may result in skin ulceration, injury to mucous membranes, perforation of nasal septum, skin cancer and keratoses, especially of the palms and soles and may cause detrimental effects. Considering the toxicity of arsenic, even if traces of arsenic from such glass containers/ampoules are leached out, it can impart damage to human beings. To check the possibility of leaching of arsenic from glass ampoules, a simple methodology has been developed. Different makes and varieties of glass ampoules filled with de-ionized water were subjected to high pressure and temperature leaching for varying amount of time using autoclave to create extreme conditions for the maximum leaching out of the analyte. Subsequently, the determination of the arsenic contents in leached water using neutron activation analysis is reported in this paper in detail with observations.