Solid phase extraction of chromium(VI) from aqueous solutions by adsorption of its diphenylcarbazide complex on a mixed bed adsorbent (acid activated montmorillonite-silica gel) column.
ABSTRACT A novel approach has been developed for the solid phase extraction of chromium(VI) based on the adsorption of its diphenylcarbazide complex on a mixture of acid activated montmorillonite (AAM)-silica gel column. The effect of various parameters such as acidity, stability of the column, sample volume, interfering ions, etc., were studied in detail. The adsorbed complex could be easily eluted using polyethylene glycol-sulfuric acid mixture and the concentration of chromium has been determined using visible spectrophotometry. The calibration graph was linear in the range 0-1microgmL(-1) chromium(VI) with a detection limit of 6microgL(-1). A highest preconcentration factor of 25 could be obtained for 250mL sample volume using glass wool as support for the mixed bed adsorbent. Chromium(VI) could be effectively separated from other ions such as nickel, copper, zinc, chloride, sulfate, nitrate, etc., and the method has been successfully applied to study the recovery of chromium in electroplating waste water and spiked water samples.
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ABSTRACT: A simple and relatively green method has been developed for the determination of chromium based on the extraction of chromium (VI) as its ion-association complex with tetrabutylammoniumiodide (TBAI) in acidic medium. The ion-pair is extracted using isobutylmethylketone (MIBK) as the solvent. The concentration of the extracted chromium (VI) in the organic layer was measured spectrophotometrically at a wavelength maximum of 366 nm and the organic layer was characterized using FT-IR spectroscopy. The influence of various analytical parameters such as pH, aqueous phase volume, equilibration time, interfering ions etc. has been studied in detail. The extracted chromium (VI) was back extracted into the aqueous phase to the non-toxic chromium (III) using ascorbic acid. The calibration graph was linear in the range of 0-2 microg mL(-1) chromium (VI) with a relative standard deviation of 2.4%. A detection limit of 0.25 microg in 25 mL aqueous phase volume could be achieved and the validity of the proposed method has been checked by applying it to synthetic mixtures, spiked water sample, electroplating wastewater and certified reference material BCR-715.Journal of hazardous materials 06/2009; 170(2-3):1079-85. · 4.14 Impact Factor
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ABSTRACT: Toxic Cr(III) which poses environmental hazard to flora and fauna was efficiently abstracted by low-cost Nauclea diderrichii seed biomass (NDS) with good sequestral capacity for this metal was investigated in this study. The NDS surface analyses showed that it has a specific surface area of 5.36 m 2 /g and pHpzc of 4.90. Thermogravimetric analysis of NDS showed three consecutive weight losses from 50–200°C (ca. 5%), 200–400°C (ca. 35%), >400°C (ca. 10%), corresponding to external water molecules, structural water molecules and heat induced condensation reactions respectively. Differential ther-mogram of NDS presented a large endothermic peak between 20–510°C suggesting bond breakage and dissociation with the ultimate release of small molecules. The experimental data showed kinetically fast biosorption with increased initial Cr(III) concen-trations, indicating the role of external mass transfer mechanism as the rate controlling mechanism in this adsorption process. The Langmuir biosorption capacity of NDS was 483.81 mg/g. The use of the corrected Akaike Information Criterion tool for ranking equilibrium models suggested that the Freundlich model best described the experimental data, which is an indication of the heterogeneous nature of the active sites on the surface of NDS.Journal of Saudi Chemical Society 11/2012; · 1.29 Impact Factor
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ABSTRACT: This is the first Atomic Spectrometry Update (ASU) to focus specifically on developments in elemental speciation and covers a period of 10 months from January 2008. Other ASU reviews1–5 detail aspects of the research in this area, but our aim is to bring all of the work on this subject together in a single review. This new development comes as a result of the importance of the currency of the ASU reviews as a series. As a consequence of the continued and growing interest in the area of elemental speciation, which is evidenced by the volume of primary and review literature on the subject and the emergence of scientific meetings focusing on the topic, it was decided to instigate a radical change to the ASU series, culminating in the development of this new Update. Speciation has been considered by the International Union for Pure and Applied Chemistry (IUPAC) who have published guidelines6 for its definition, which are as follows: speciation analysis is the analytical activity of identifying and/or measuring the quantities of one or more individual chemical species in a sample; the chemical species are specific forms of an element defined as to isotopic composition, electronic or oxidation state, and/or complex or molecular structure; the speciation of an element is the distribution of an element amongst defined chemical species in a system. This review will therefore deal with all aspects of the analytical speciation methods developed for: the determination of oxidation states; organometallic compounds; coordination compounds; metal and heteroatom-containing biomolecules, including metalloproteins, proteins, peptides and amino acids; and the use of metal-tagging to facilitate detection via atomic spectrometry. Applications in the areas of environmental science, clinical and pharmaceutical analysis, food, industrial and related areas will be covered. The review will not specifically deal with operationally defined speciation, but will highlight other reviews which cover the work in this area. As with all ASU reviews, the coverage of the topic is confined to those methods that incorporate atomic spectrometry as the measurement technique. However, in the spirit of meeting the needs of the subject, we will incorporate material that is not strictly “atomic spectrometry”. For the most part, such procedures are those in which some form of molecular MS is the measurement technique. There is a growing role for this kind of MS either as the sole instrumental technique or quite literally, in parallel with an elemental detector. As the contents of this Update show, there is considerable activity in the development and application of methods of elemental speciation analysis, which for some elements and combinations of techniques is a mature field as shown by the extent to which relevant topics have been the subject of reviews and book chapters.Journal of Analytical Atomic Spectrometry 01/2009; 24(8):999-1025. · 3.16 Impact Factor