[en] A rapid accurate, and precise method has been developed for the determination of uranium in brines with > 5 ppb of uranium. The procedure involves coprecipitation of uranium with ferric hydroxide followed by its dissolution in dilute nitric acid and determination by laser fluorimetry. There is no need to separate iron though it is a quencher element. The relative standard deviation in the range of 5-30 ppb is ± 15%. (author). 11 refs., 3 tabs., 2 figs

[en] This paper presents the investigation carried out on a new solid phase adsorbent developed in our laboratory, xylenol orange immobilized on silica (XO-Si) by a single step process. Preparation of silica from sodium meta-silicate solution and immobilization of xylenol orange on it takes place simultaneously in presence of cationic surfactant cetyl-tri-methyl ammonium bromide (CTAB). It was observed that in the absence of surfactant, xylenol orange was completely removed from the silica surface during washing. The surfactant CTAB acts as a bridge between silica and xylenol orange molecule

[en] A simple and economical method for the removal of uranium from Gogi mine water using the powdered red brick as a good adsorbent is discussed. Preliminary studies for the removal of uranium using brick showed encouraging results. Further studies were carried to find the amount and size of brick for the quantitative removal of uranium. The results of these studies showed that 50 g of brick with 10 mesh size was enough to remove uranium quantitatively from 100 ml of mine water containing 1800 μg/L of uranium. However the column studies indicated considerable decrease (∼ 5 g for 100 ml of mine water) in the amount of brick required to remove uranium from 100 ml of mine water

[en] Oxalate precipitation of lanthanides in acidic medium is a widely used selective group separation method at percentage to trace level in different types of geological samples. Most of the procedures are based on the heterogeneous oxalate precipitation of lanthanides using calcium as carrier. In the heterogeneous precipitation, the co-precipitated impurities from the matrix elements are more, besides if the pH at the time of precipitation is not monitored carefully there is a chance of losing some of the lanthanides. In this report, we present a new homogeneous oxalate precipitation of trace level lanthanides from different types of geological samples using calcium as carrier. In the present method pH is getting adjusted (pH ∼1) on its own, after the hydrolysis of urea added to the sample solution. This acidic pH is essential for the complete precipitation of the lanthanides. Therefore, no critical parameter adjustment for the precipitation is involved in the proposed method. The oxalate precipitate obtained was in crystalline nature which facilitates the fast settlement, easy filtration; besides the co-precipitated matrix elements are very less as compared to normal heterogeneous oxalate precipitation of lanthanides. Another advantage is more quantity of the sample can be taken for the separation of lanthanides which is a limitation for other separation methods reported. Accuracy of the method was checked by analyzing nine international reference materials comprising different types of geological samples obtained from Canadian Certified Reference Project Materials such as syenite samples SY-2, SY-3 and SY-4; gabro sample MRG-1; soil samples SO-1 and SO-2; iron formation sample FeR-2; lake sediments LKSD-2 and LKSD-4. The values of the lanthanides obtained for these reference materials are comparable with recommended values, indicating that the method is accurate. The reproducibility is characterized by a relative standard deviation (RSD) of 1 to 6% (n=4). (author)

[en] Niobium (Nb) and Tantalum (Ta) are rare metals and they present in the rock samples at trace levels and their variation in rock samples is used as an indicator for certain geochemical process within the crust-mantle system. The Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES) determination of Nb and Ta at trace levels in geological samples suffers from spectral and non-spectral interferences due to matrix elements. Therefore, a selective quantitative separation of both Nb and Ta from rock samples matrix is necessary for their accurate determination. In the present report a simple, selective hydroxide precipitation separation of both Nb and Ta present in the geological samples is developed. Rock samples are treated with a mixture hydrochloric acid and hydrofluoric acid initially, and finally with perchloric acid. The sample solution is prepared in 5% (v/v) hydrochloric acid. Then hydroxide precipitation of both Nb and Ta is carried out using dilute ammonia solution in the presence of ammonium EDTA and Sn (IV) as carrier. The precipitate after filtration is re-dissolved in a hydrochloric acid, oxalic acid and hydrogen peroxide solution. The Nb and Ta are determined by ICP-AES using emission lines at 316.340 nm for Nb, and 240.063 nm for Ta respectively. Accuracy of the method was checked using Standard Reference Materials, niobium ore CANMET OKA-1, tantalum ore CANMET TAN-1, and syenite CANMET SY-3. The values obtained are in close agreement with the recommended values. The reproducibility is characterized by a relative standard deviation (RSD) of 1 to 6% (n=4). The present method was applied to determine Nb and Ta above 10 μg g"-"1 in the mineralized rock samples. (author)

[en] The determination of lanthanides play an important role in geology as their distribution pattern is widely used for the petrogenetic studies. These elements are present at trace level; therefore the accurate determination of these elements is a difficult task. The ICP-AES is a commonly used instrumental technique for the determination of lanthanides at trace levels, due to its good sensitivity. However, ICP-AES suffers from spectral interference from the major and minor matrix elements in geological materials. Therefore, a selective separation of the trace level lanthanides from the matrix elements is needed. This paper reports a selective homogeneous oxalate precipitation of trace level lanthanides using calcium as carrier

[en] The hydrogeochemical survey for uranium is done not only for the determination of uranium but also that of other geochemically important elements Cu, Co, Ni, Pb, Cd, Cr, Zn, Mo and V that are likely to accompany uranium. They play an important role as they are useful in the understanding of petro-genetic and ore-genetic processes. These elements also accompany uranium in its various types of deposits and therefore can be used in geochemical surveys as pathfinder elements. For sandstone type and vein type uranium deposits, Mo acts as one of the pathfinder elements. Since Mo is present at the nanogram level in the hydrogeochemical samples, various pre-concentration techniques such as liquid-liquid extraction, ion-exchange separation, coprecipitation and solid phase extraction can be used. Use of different types of abundant biological materials such as chitin, chitosan, saw dust, biomass, vegetable mass etc. as solid phase extractants has gained popularity for the preconcentration of metals like Mo due to its flexibility, higher enrichment factor, absence of emulsions, rapidity and cost effectiveness. In the present study, coconut husk, an agricultural waste, has been thoroughly investigated for the pre-concentration of Mo in hydrogeochemical samples prior to its analysis. This material has been used by other workers for the removal of toxic metal ions such as Cd, Cr, Hg, Pb, Cu and As for environmental protection. Pre-concentrated molybdenum, after adsorption, has been leached with suitable reagent and then analyzed by ICP-OES

[en] A simple, selective and rapid determination procedure for Th, Zr and Sc in rock samples using adsorbent silica modified with arsenazo-III is described. Silica modified with arsenazo-III (SAR-III) was synthesised by a single step process in presence of cationic surfactant cetyltrimethylammonium bromide. Effect of pH, amount of adsorbent, contact time for adsorption and the optimum eluent for the quantitative recovery of Th, Zr and Sc were investigated. Optimum conditions selected for the selective extraction of these elements by SAR III are pH-3, 0.2 g adsorbent, contact time 30 minutes and 10 mL of 5 % ammonium oxalate as eluent. Adsorption capacities of SAR III for Th, Zr and Sc are 5.68, 23.9 and 4.42 mg g⁻¹, respectively. Effect of major elements present in the rock on the pre-concentration of these elements was investigated. Interference of iron was eliminated by reducing ferric iron with hydroxylamine hydrochloride. The method was validated by applying the procedure to synthetic rock sample solutions and certified geological reference materials SY-2 (CCRMP, Canada), BCR-1 (USGS), GSN (ANRT, France) and AGV-1(USGS). Detection limits obtained for Th and Zr by this method are 1 µg g⁻¹ and that of Sc is 0.1 µg g⁻¹. The relative standard deviation of the method at 1 µg g⁻¹ was in the range of 1.0–2.5%.

Graphic abstract

Synthesis of silica modified arsenazo-III and its application for the determination of Zr, Th and Sc in rock samples by ICP- AES is described. The result of this study indicates silica modified with arsenazo-III as very selective and sensitive solid phase extractant for Zr, Sc and Th in presence of all the other major elements of rock.

[en] Xenotime mineral is the main source of yttrium which is used for making crystals of the yttrium-aluminium garnet (YAG), yttrium-iron-garnet (YIG), phosphors (Eu:Y_O3) to create red colour in television and several other high-tech industrial applications. The chemical composition of the mineral is YPO₄, with Y and P as major elements with minor quantities of certain heavy rare earth elements (HREE) like Dy, Er and Yb. The light rare earth elements (LREE) especially the first three members La, Ce and Pr are often present at very low level, therefore, their direct accurate ICP-AES determination is difficult due to the spectral interference caused by the presence of mg/ml amounts of Y and phosphate, besides changing the plasma characteristics at that salt load level. In the literature their values are often not quoted due to the difficulty in accurate determination. This paper summarises the method developed for the separation of bulk of the HREE from LREE in xenotime mineral which facilitate spectral interference free ICP-AES determination REE and Y particularly La, Ce and Pr. (author)

[en] A simple, selective and rapid determination procedure for Th, Zr and Sc in rock samples using adsorbent silica modified with arsenazo-III is described. Silica modified with arsenazo-III (SAR-III) was synthesised by a single step process in presence of cationic surfactant cetyltrimethylammonium bromide. Effect of pH, amount of adsorbent, contact time for adsorption and the optimum eluent for the quantitative recovery of Th, Zr and Sc were investigated. Optimum conditions selected for the selective extraction of these elements by SAR III are pH-3, 0.2 g adsorbent, contact time 30 minutes and 10 mL of 5 % ammonium oxalate as eluent. Adsorption capacities of SAR III for Th, Zr and Sc are 5.68, 23.9 and 4.42 mg g^-1 , respectively. Effect of major elements present in the rock on the pre-concentration of these elements was investigated. Interference of iron was eliminated by reducing ferric iron with hydroxylamine hydrochloride. The method was validated by applying the procedure to synthetic rock sample solutions and certified geological reference materials SY-2 (CCRMP, Canada), BCR-1 (USGS), GSN (ANRT, France) and AGV-1(USGS). Detection limits obtained for Th and Zr by this method are 1 lg g^-1 and that of Sc is 0.1 μg g^-1 . The relative standard deviation of the method at 1 μg g^-1 was in the range of 1.0-2.5%. (author)