Somia B. Ahmed

Speciation, selective extraction and preconcentration of chromium ions via alumina-functionalized-isatin-thiosemicarbazone

A method is presented and described for speciation, extraction and preconcentration of Cr(III) and Cr(VI) based on dynamic and static solid phase extraction techniques. Three newly designed alumina phases-physically adsorbed-isatin-thiosemicarbazone (I-III) were synthesized, characterized, tested for stability and applied as inorganic ion exchangers and chelating solid sorbents for various metal ions. The selectivity characteristics incorporated into these alumina phases were studied and evaluated via determination of the distribution coefficients and separation factors of chromium species versus other interacting metal ions. Quantitative recovery of Cr(VI) was accomplished by alumina phases (I-III) in pH 1.0 giving percentage extraction values of approximately 99.9-100.0%, while Cr(III) was found to be quantitatively recovered by these sorbents in pH 7.0 leading to percentage extraction values approximately 100.0% with minimal or no interference between these two species under the studied buffering conditions. Selective solid phase speciation and preconcentration of Cr(III) and Cr(VI) in various real water samples were successfully performed and accomplished by newly designed alumina phases (I-III) via a preconcentration micro-column.

Development of a Method for Chromium Speciation by Selective Solid Phase Extraction and Preconcentration on Alumina-Functionalized Thiosemicarbazide

Abstract A speciation method is developed for Cr(III) and Cr(VI) at selected medium pH range via solid phase extraction on three designed and synthesized chelating inorganic solid sorbents based on adsorption of thiosemicarbazide, as the nitrogen and sulfur containing chelating compound, on alumina surface [Al-TSC (I–III)]. The influence of various parameters including medium pH, time of contact, and interference of matrix and coexistent elements on the speciation and selective extraction processes of chromium species are studied and evaluated on the basis of determination of the metal adsorption capacity, distribution coefficient, and separation factor. Quantitative recovery of Cr(VI) was accomplished by [Al-TSC (I–III)] at pH = 1.0, while Cr(III) was found to be recovered on these sorbents at pH = 7.0 with minimal or no interference between these two species under the studied buffering conditions. The proposed method has been successfully applied for speciation, selective extraction, and preconcentration of Cr(III) and Cr(VI) in water samples with a preconcentration factor of 200.

Chromium speciation, selective extraction and preconcentration by alumina-functionalised 2-pyridenecarboxyladehyde thiosemicarbazone

A method is proposed and explored for speciation of Cr(III) and Cr(VI), selective extraction and preconcentration in various water samples based on dynamic and static techniques. Three newly designed alumina phases-physically adsorbed-2-pyridenecarboxyladehyde-thiosemicarbazone [Al-2PC-TSC (I–III)] were synthesised and characterised. Stability tests and application of [Al-2PC-TSC (I–III)] as inorganic ion exchangers and chelating solid sorbents for various metal ions were studied and evaluated. The distribution coefficient and separation factors of chromium species versus other interfering metal ions were determined to examine the incorporated selectivity into these alumina phases. Quantitative recovery of Cr(VI) was accomplished by [Al-2PC-TSC (I–III)] at pH = 1.0 while Cr(III) was found to be quantitatively recovered on these sorbents at pH = 7.0 with minimal or no interference between these two species under the studied buffering conditions. Selective solid phase speciation and preconcentration of Cr(III) and Cr(VI) in various real water samples were successfully performed and accomplished via a micro-column, with 200 as a preconcentration factor. Selective speciation of Cr(VI) and Cr(III) via preconcentration from seawater and industrial water samples by alumina phases in pH = 1 was found to give percentage recovery values of Cr(VI) in the range 93.5–97.3 ± 3.0–5.0% and 94.0–97.5 ± 3.0–4.0%, for seawater and industrial water samples, respectively.

Magnetically active biosorbent for chromium species removal from aqueous media

A magnetically active composite as adsorbent was synthesized via a facile in situ one-pot impregnation of magnetic nano-iron oxide (Fe3O4) on the surface of activated carbon (AC) for the formation of AC-Fe3O4. Baker’s yeast was physically loaded on the resultant adsorbent AC-Fe3O4 to form a novel yeast coated magnetic composite AC-Fe3O4-Yst as biosorbent. The two synthesized adsorbents were characterized by using a scanning electron microscope (SEM) and assessed using Langmuir, the Brunauer-Emmet-Teller (BET) and Dubinin-Radushkevich (D-R) isotherm models. The validity and applicability of these two sorbents in adsorptive removal of chromium species, Cr(VI) and Cr(III), from aqueous solutions under the effect of a magnetic field were studied and evaluated in the presence of various controlling parameters in order to identify the optimal pH, contact time, mass dose and chromium concentrations for such adsorption process. Also, single and multi-stage micro-column techniques were used to study the potential applications of AC-Fe3O4 as magnetically active adsorbents and AC-Fe3O4-Yst as magnetically active biosorbents, for the removal of chromium species from various real water samples.

Chemically and biologically modified activated carbon sorbents for the removal of lead ions from aqueous media

A method is described for hybridization of the adsorption and biosorption characteristics of chemically treated commercial activated carbon and bakers yeast, respectively, for the formation of environmental friendly multifunctional sorbents. Activated carbon was loaded with bakers yeast after acid-base treatment. Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) Spectroscopy were used to characterize these sorbents. Moreover, the sorption capabilities for lead (II) ions were evaluated. A value of 90 μmol g−1 was identified as the maximum sorption capacity of activated carbon. Acid-base treatment of activated carbon was found to double the sorption capacity (140–180 μmol g−1). Immobilization of bakers yeast on the surface of activated carbon sorbents was found to further improve the sorption capacity efficiency of lead to 360, 510 and 560 μmol g−1, respectively. Several important factors such as pH, contact time, sorbent dose, lead concentration and interfering ions were examined. Lead sorption process was studied and evaluated by several adsorption isotherms and found to follow the Langmuir and BET models. The potential applications of various chemically and biologically modified sorbents and biosorbents for removal of lead from real water matrices were also investigated via multistage micro-column technique and the results referred to excellent recovery values of lead (95.0–99.0 ± 3.0–5.0 %).

Enhanced removal of lead by chemically and biologically treated carbonaceous materials.

Hybrid sorbents and biosorbents were synthesized via chemical and biological treatment of active carbon by simple and direct redox reaction followed by surface loading of bakers yeast. Surface functionality and morphology of chemically and biologically modified sorbents and biosorbents were studied by Fourier Transform Infrared analysis and scanning electron microscope imaging. Hybrid carbonaceous sorbents and biosorbents were characterized by excellent efficiency and superiority toward lead(II) sorption compared to blank active carbon providing a maximum sorption capacity of lead(II) ion as 500 μmol g−1. Sorption processes of lead(II) by these hybrid materials were investigated under the influence of several controlling parameters such as pH, contact time, mass of sorbent and biosorbent, lead(II) concentration, and foreign ions. Lead(II) sorption mechanisms were found to obey the Langmuir and BET isotherm models. The potential applications of chemically and biologically modified-active carbonaceous materials for removal and extraction of lead from real water matrices were also studied via a double-stage microcolumn technique. The results of this study were found to denote to superior recovery values of lead (95.0–99.0 ± 3.0–5.0%) by various carbonaceous-modified-bakers yeast biosorbents.