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.
SourceAvailable from: Krystyna Pyrzynska[Show abstract] [Hide abstract]
ABSTRACT: The difference in toxicity is one of the main reasons for the recent development of analytical procedures for differentiating chromium (Cr) species. Non-chromatographic speciation procedures using sorption-based systems offer very convenient tools and can be used as fast, cheap alternatives to chromatography. The methods based on sorbent extraction have proved to be the most attractive, due to their high separation and preconcentration efficiency.This review presents procedures based on sorption principles for use in Cr-speciation analysis. They are discussed and compared in terms of selectivity and efficiency. This review covers the state of the art since 2005.TrAC Trends in Analytical Chemistry 02/2012; 32:100-112. DOI:10.1016/j.trac.2011.09.004 · 6.61 Impact Factor
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ABSTRACT: This paper describes the treatment of montmorillonite (MT), with K+ (MTK), Na+ (MTNa), and Ca2+ (MTCa) to explore the use of these minerals for the extraction and preconcentration of the herbicides atrazine, simazine, and ametryne from aqueous medium. In the sorption process, the three materials exhibited good performance; ametryne was totally sorbed. For atrazine and simazine, MTK showed a removal between 90% (atrazine) and higher than 99% (simazine). The recoveries employing solutions at initial concentrations of 100 µg L−1 of each herbicide showed results of 90% (simazine) and 94% (atrazine), whereas for 10 µg L−1, the results of 73% (simazine) and 81% (atrazine) were obtained. On the other hand, ametryne showed poor recovery values (25 to 40%), probably due to a stronger interaction with MTK, lowering the recovery values. Based on the results for atrazine and simazine, MTK presented good features to be used as sorbent phase and for preconcentration, being easily prepared with low cost, demanding low amounts to be used for this purpose, providing fast sorption of atrazine and simazine, and with appropriate recoveries.Analytical Letters 02/2013; 46(3). DOI:10.1080/00032719.2012.725191 · 0.98 Impact Factor
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ABSTRACT: Ice nucleation properties of atmospherically relevant dust minerals coated with soluble materials are not yet well understood. We determined ice nucleation ability of bare and sulfuric acid coated mineral dust particles as a function of temperature (−25 to −35 °C) and relative humidity with respect to water (RHw; 75 to 110 %) for five different mineral dust types: 1) Arizona test dust (ATD), 2) illite, 3) montmorillonite, 4) K-feldspar, and 5) quartz. The particles were dry-dispersed and size-selected at 200 nm, and we determined the fraction of dust particles nucleating ice at various temperatures and RHw. Under water-subsaturated conditions, compared to bare dust particles, we found that coated particles showed a reduction in their ice nucleation ability. Under water-supersaturated conditions, however, we did not observe a significant coating effect (i.e., the bare and coated dust particles had nearly similar nucleating properties). X-ray diffraction patterns of the coated particles indicated that acid treatment altered the crystalline nature of the surface and caused structural disorder; thus, we concluded that the lack of such structured order reduced the ice nucleation efficiency of the coated particles in deposition ice nucleation mode. In addition, our single column model results show that coated particles significantly modify cloud properties such as ice crystal number concentration and ice water content compared to bare particles in water-subsaturated conditions. However, in water-supersaturated conditions, cloud properties differ only at warmer temperatures. These modeling results imply that future aged dust particle simulations should implement coating parameterizations to accurately predict cloud properties.Journal of Geophysical Research Atmospheres 08/2014; DOI:10.1002/2014JD021567 · 3.44 Impact Factor