Adsorption of transition-metal ions in ethanol solution by a nanomaterial based on modified silsesquioxane

The material octakis[3-(3-amino- 1,2,4-triazole)propyl]octasilsesquioxane (ATZ-SSQ) was synthesized and its potential was assessed for Cu(II), Ni(II), Co(II), Zn(II) and Fe(III) from their ethanol solutions and compared with related 3-amino-1,2,4-triazole-propyl modified silica gel (ATZ-SG). The adsorption was performed using a batchwise process and both organofunctionalized surfaces showed the ability to adsorb the metal ions from ethanol solution. The Langmuir model allowed to describe the sorption of the metal ions on ATZ-SSQ and ATTZ-SG in a satisfactory way. The equilibrium is reached very quickly Q min) for ATZ-SSQ, indicating that the adsorption sites are well exposed. The maximum metal ion uptake values for Cu(II), Co(II), Zn(II), Ni(II) and Fe(III) were 0.86, 0.09, 0.19, 0.09 and 0.10 mmol g(-1), respectively, for the ATZ-SSQ, which were higher than the corresponding values 0.21, 0.04, 0.14, 0.05 and 0.07 mmol g(-1) achieved with the ATZ-SG. In order to obtain more information on the metal-ligand interaction of the complexes on the surface of the ATZ-SSQ, Cu(II) was used as a probe to determine the arrangements of the ligands around the central metal ion by electron spin resonance (ESR). The ATZ-SSQ was used for the separation and determination (in flow using a column technique) of the metal ions present in commercial ethanol. (c) 2008 Elsevier B.V. All rights reserved.

Determination of Cd(II), Cu(II) and Ni(II) in aqueous samples by ICP-OES after on-line preconcentration in column packed with silica modified with 2-aminothiazole

This work describes the synthesis and characterization of 2-aminothiazole modified silica gel (SiAT) and the studies of adsorption and pre-concentration (in batch and using a flow-injection system coupled with optical emission spectrometer) of Cd(II), Cu(II) and Ni(II) in aqueous medium. The adsorption capacity for each metal ions in mmolg(-1) was: Cu(II) = 1.18, Ni(II) = 1.15 and Cd(II) = 1.10. The results obtained in the flow experiments showed about 100% of recovering of the metal ions adsorbed in a mini-column packed with 100 mg of SiAT, using 100 mu L of 2.0 mol L-1 HCl solution as eluent. The quantitative sorption-desorption of the metal ions made possible the application of a flow-injection system in the pre-concentration and quantification by ICP-OES of metal ions at trace level in natural water samples.

Determination of Cu, Ni, and Zn in fuel ethanol by FAAS after enrichment in column packed with 2-aminothiazole-modified silica gel

This work describes the synthesis and characterization of 2-aminothiazole-modified silica gel (SiAT), as well as its application for preconcentration (in batch and column technique) of Cu(II), Ni(II) and Zn(II) in ethanol medium. The adsorption capacities of SiAT determined for each metal ion were (mmol g(-1)): Cu(II)=1.20, Ni(II)=1.10 and Zn(II)=0.90. In addition, results obtained in flow experiments, showed a recovery of ca. 100% of the metal ions adsorbed in a column packed with 500 mg of SiAT. The eluent was 2.0 mol L-1 HCl. The sorption-desorption of the studied metal ions made possible the development of a preconcentration method for metal ions at trace level in fuel ethanol using flame AAS for their quantification.

Determination of Copper, Iron, Nickel and Zinc in fuel kerosene by FAAS after adsorption and pre-concentration on 2-aminothiazole-modified silica gel

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Pre-concentration of Cd(II), Cr(III), Cu(II) and Ni(II) on a column packed with oxycellulose.

Oxycellulose (OXICEL) was packed in a glass column to pre-concentrate metal cations from aqueous solutions. The pre-concentrated metal cations are directly eluted from the column using 5.0 mL of 1.0 mol L(-1) hydrochloric acid. The optimum pre-concentration conditions are given and the retention efficency achieved is higher than 95%. The enrichment factor is 10 for sample volumes of 50 mL.

Study of an organically modified clay: Selective adsorption of heavy metal ions and voltammetric determination of mercury(II)

In this work, a hydrophilic clay, Na-montmorillonite from Wyoming, USA, was rendered organophilic by exchanging the inorganic interlayer cations for hexaclecyltrimethylammonium ions (HDTA), with the formulae of [(CH3)(3)N(C16H33)](+) ion. Based on fact that organo-clay has high affinities for non-ionic organic molecules, 1,3,4-thiadiazole-2,5-dithiol was loaded oil the HDTA-montmorillonite surface, resulting in the 1,3,4-thiadiazole-2,5-dithiol-HDTA-montmorillonite complex (TDD-organo-clay).The following properties of TDD-organo-clay are discussed: selective adsorption of heavy metal ions measured by batch and chromatographic column techniques, and utilization as preconcentration agent in a chemically modified carbon paste electrode (CMCPE) for determination of mercury(II).The main point of this paper is the construction of a selective sensor, a carbon paste electrode modified with TDD-organo-clay, its properties and its application to the determination of mercury(II) ions, as this element belongs to the most toxic metals. The chemical selectivity of this functional group and the selectivity of voltammetry were combined for preconcentration and determination. (c) 2005 Elsevier B.V. All rights reserved.

Adsorption of Cu(II), Zn(II), Cd(II), Hg(II) and Pb(II) from aqueous solutions on a 2-mercaptobenzimidazole-modified silica gel

The chemically modified silica, obtained by reacting 2-mercaptobenz-imidazole with 3-chloropropyl silica gel, was used to adsorb Cu(II), Zn(II), Cd(II) and Pb(II) from aqueous solutions at various pH. Between pH 3-5, the order of selectivity was Hg(II) > Cd(II) ≫ Cu(II) ∼ Zn(II) ∼ Pb(II). Under batch conditions retentions of 100% were achieved for all metals except for Pb(II) where 93% was attained. Under column conditions recoveries of 100% were obtained for all metals. © 1990 Springer-Verlag.

Pre-concentration of Cd(II), Cr(III), Cu(II) and Ni(II) on a column packed with free carboxymethylcellulose (CMCH)

Carboxymethylcellulose packed in to a glass column was used to pre-concentrate metallic cations from aqueous solutions. The pre-concentrated metal cations are directly eluted from the column using 5.0 mL of 1.0 mol L -1 hydrochloric acid. The optimum pre-concentration conditions are given (glass column, 16 cm length, 0.80 cm i.d., stationary phase height of 12 cm, flow-rate, 1.5 mL min -1). The recuperation efficiency achieved is greater than 95%, while the enrichment factor is 10 for 50 mL of solution (0.50 mg L -1 each).

Determination of cadmium in river water samples by flame AAS after on-line preconcentration in mini-column packed with 2-aminothiazole-modified silica gel

A rapid and sensitive method was developed to determine trace levels of Cd2+ ions in an aqueous medium by flame atomic absorption spectrometry, using on-line preconcentration in a mini-column packed with 100 mg of 2-aminothiazol modified silica gel (SiAT). The Cd2+ ions were sorbed at pH 5.0. The preconcentrated Cd2+ ions were directly eluted from the column to the spectrometer's nebulizer-burner system using 100 μL of 2 mol L-1 hydrochloric acid. A retention efficiency of over 95% was achieved. The enrichment factor (calculated as the ratio of slopes of the calibration graphs) obtained with preconcentrations in a mini-column packed with SiAT (A = -1.3 × 10-3 + 1.8 × 10-3 [Cd2+]) and without preconcentrations (A = 4 × 10-5 + 3.5 × 10-3[Cd2+]), was 51 and the detection limit calculated was 0.38 μg L-1. The preconcentration procedure was applied to determine trace levels of Cd in river water samples. The optimum preconcentration conditions are discussed herein.

Preparation of a silica gel modified with 2-amino-1,3,4-thiadiazole for adsorption of metal ions and electroanalytical application

Silica gel with a specific area of 382 m2 g-1 and an average pore diameter of 60 Å was chemically modified with 2-amino-1,3,4-thiadiazole, for the purpose of selective adsorption of heavy metals ions and possible use as a chemically modified carbon paste electrode (CMCPE). The following properties of this functionalized silica gel are discussed: selective adsorption of heavy metal ions measured by batch and chromatographic column techniques, and utilization as preconcentration agent in a chemically modified carbon paste electrode (CMCPE) for determination of mercury(II). The chemical selectivity of this functional group and the selectivity of voltammetry were combined for preconcentration and determination. ©2006 Sociedade Brasileira de Química.

Study of adsorption and preconcentration by using a new silica organomodified with [3-(2,2′-dipyridylamine)propyl] groups

In this work, a silica surface chemically modified with [3-(2,2′-dipyridylamine)propyl] groups, named [3-(2,2′- dipyridylamine)propyl]silica (Si-Pr-DPA) was prepared, characterized, and evaluated for its heavy metal adsorption characteristics from aqueous solution. To our knowledge, we are the first authors who have reported the present modification. The material was characterized using infrared spectroscopy, SEM, and NMR 29Si and 13C solid state. Batch and column experiments were conducted to investigate for heavy metal removal from dilute aqueous solution by sorption onto Si-Pr-DPA. From a number of studies the affinity of various metal ions for the Si-Pr-DPA sorbent was determined to follow the order Fe(III) > Cr(III) >> Cu(II) > Cd(II) > Pb(II) > Ni(II). Two standard reference materials were used for checking the accuracy and precision of the method. The proposed method was successfully applied to the analysis of environmental samples. This ligand material has great advantage for adsorption of transition-metal ions from aqueous medium due to its high degree of organofunctionalization associated with the large adsorption capacity, reutilization possibility, and rapidity in reaching the equilibrium. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An electroanalytical application of 2-aminothiazole-modified silica gel after adsorption and separation of Hg(II) from heavy metals in aqueous solution

2-Aminothiazole covalently attached to a silica gel surface was prepared in order to obtain an adsorbent for Hg(II) ions having the following characteristics: good sorption capacity, chemical stability under conditions of use, and, especially, high selectivity. The accumulation voltammetry of mercury(II) was investigated at a carbon paste electrode chemically modified with silica gel functionalized with 2-aminothiazole (SIAMT-CPE). The repetitive cyclic voltammogram of mercury(II) solution in the potential range -0.2 to + 0.6 V versus Ag/AgCl (0.02 mol L-1 KNO3; V = 20 mV s(-1)) show two peaks one at about 0.1 V and other at 0.205 V. The anodic wave peak at 0.205 V is well defined and does not change during the cycles and it was therefore further investigated for analytical purposes using differential pulse anodic stripping voltammetry in differents supporting electrolytes. The mercury response was evaluated with respect to pH, electrode composition, preconcentration time, mercury concentration, cleaning solution, possible interferences and other variables. The precision for six determinations (n = 6) of 0.02 and 0.20 mg L-1 Hg(II) was 4.1 and 3.5% (relative standard deviation), respectively. The detection limit was estimated as 0.10 mu g L-1 mercury(II) by means of 3:1 current-to-noise ratio in connection with the optimization of the various parameters involved and using the highest-possible analyser sensitivity. (c) 2006 Elsevier Ltd. All rights reserved.

Kinetics and Adsorption Isotherms of Bisphenol A, Estrone, 17 beta-Estradiol, and 17 alpha-Ethinylestradiol in Tropical Sediment Samples

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Nickel adsorption by soils in relation to pH, organic matter, and iron oxides

There is little information on nickel adsorption by Brazilian soils. The objective of this experiment was to determine the effect of pH, organic matter, and iron oxides on nickel adsorption by three soils: a clayey Anionic Rhodic Acrudox, a sandy clay loam Anionic Xanthic Acrudox, and a clayey Rhodic Hapludalf. Soil samples were collected from the 0-0.2 in layer and treated to eliminate organic matter and iron oxides. The nickel adsorption was evaluated in the original samples and in those treated to remove organic matter and to remove both, organic matter and iron oxides, using 2 g soil + 20 mL of 0.01 mol L-1 CaCl2 solution containing 5 mg L-1 Ni, pH varying from 3.5 to 7.5. The nickel adsorption decreased with the elimination of organic matter. For the samples without organic matter and iron oxides, adsorption decreased only in the Anionic Rhodic Acrudox. The pH was the main factor involved in nickel adsorption variation, and for soil samples without organic matter and iron oxides, the maximum adsorption occurred at higher pH values.