Immobilization of ethylenesulfide on silica surface through sol-gel process and some thermodynamic data of divalent cation interactions

The silylant precursor agent 3-aminopropyltrimethoxysilane (APTS) reacted with ethylenesulfide to yield 2-{2-{3-(trimethoxysilyl)propylamino}ethylthio}-ethanethiol, which was anchored on silica gel by using the sol-gel process. The new synthetic silylant agent displayed a chelating moiety containing one nitrogen and two sulfur basic centers, which are potentially favored for adsorbing divalent cations from aqueous solution. Thus. the similar chemisorption isotherms for all cations were obtained by batchwise method and the data were adjusted to a modified Langmuir equation to give the sequence of the maximum retention capacity as Cu > Co > Ni. The same adsorption was followed by calorimetric titration and the enthalpic values of -7.40 +/- 0.01, -1.50 +/- 0.10 and -0.98 +/- 0.02 kJ mol(-1) for copper, nickel and cobalt respectively, were obtained. From the calculated Gibbs free energy -25.8 +/- 0.1. -35.1 +/- 0.1 and -30.8 +/- 0.1 kJ mol(-1), the variation in entropy were also obtained as 62 +/- 1, 42 +/- 1 and 100 +/- 1 J K-1 mol(-1) for the same above sequence. All thermodynamic values are in agreement with the spontaneity of the proposed cation-basic center interactions for these chelating processes. (C) 2001 Elsevier Science Ltd. All rights reserved.204192192993

Adsorption and separation of cations on chemically modified silica gel synthesised via the sol-gel process

The reaction of ethylene sulfide [(H2C)(2)S] with 3-aminopropyltrimethoxysilane resulted in a new silylating agent, which was anchored onto a silica surface via the sol-gel procedure. The synthesised silica gel surface has been used to adsorb divalent cations from aqueous solutions at room temperature. The series of isotherms of adsorption were adjusted to a modified Langmuir equation from data obtained by suspending the solid in water with MCl2 (M=Cu, Ni, Co, Pb and Hg) solutions, which gave the maximum number of moles adsorbed as 1.66, 1.44, 1.26, 1.90 and 8.51 mmol g(-1), respectively. The immobilised surface was also used for the separation of these five cations in a column. Column resolution, R-(s), was determined for all cations as the ability of the surface to separate metal ions, determined as R(s)Co-Ni=0.20, R(s)Co-Cu=0.73, R(s)Co-Pb=2.50, R(s)Co-Hg=1.73, R(s)Ni-Cu=0.55, R(s)Ni-Pb=2.25, R(s)Ni-Hg=1.69, R(s)Cu-Pb=1.33, R(s)Cu-Hg=1.52 and R(s)Pb-Hg=1.35.142206220

Adsorption and separation of cations on silica gel chemically modified by homogeneous and heterogeneous routes with the ethylenimine anchored on thiol modified silica gel

Ethyleneimine (etn) has been covalently bonded onto silica gel via homogeneous (SiSN1) and heterogeneous (SiSN2) routes. Both synthesised silica gel surfaces have been applied to adsorb divalent cations from aqueous solution at room temperature. The series of isotherms of adsorption were adjusted to a modified Langmuir equation. after collecting the data from the solid/MCl2 solution (M = Co, Ni, Cu, Pb and Hg) interfaces. The maximum adsorption were 1.08, 1.20, 1.70, 1.34 and 4.02 mmol g(-1) for SiSN1 and 0.72, 1.74, 1.91, 2.19 and 2.89 mmol g(-1) for SiSN2, for a the sequence of divalent cations: Co, Ni, Cu, Pb and Hg, respectively. Columns loaded with immobilised silica show resolutions (R) for separating metal ion couples: RCo-Ni=0.22, RCo-Pb=0.76, RCo-Cu=1.12. : RCo-Hg=2.06, RNt-Pb=0.50, RNi-Cu=1.17. RNi-Hg=2.38, RPb-Cu=0.33, RPb-Hg=1.83 and RCu-Hg=1.60 for the SiSN1 surface. The sequence: RCo-Ni=1.10, RCo-Pb=1.44. RCo-Co=1.63. : RCo-Hg=2.26, RNi-Pb=0.08, RNi-Cu=0.33, RNi-Hg=1.40, RPb-Cu=0.38, RPb-Hg=1.82 and RCu-Hg=1.55 was determined for SiSN2.o TEXTO COMPLETO DESTE ARTIGO, ESTARÁ DISPONÍVEL À PARTIR DE AGOSTO DE 2015.41424

Ethyleneimine anchored on thiol-modified silica gel surface - Adsorption of divalent cations and calorimetric data

Activated silica gel was previously modified by the silylant agent 3-mercaptopropyltrimethoxysilane. The organofunctionalized silica gel containing pendant groups ended with the -SH functions reacted with the three-member cyclic ethyleneimine molecules to yield the new ligand attaching sulfur and nitrogen basic centers available to complex cations. This final anchored surface adsorbs MX2 (M = Co2+, Ni2+, Cu2+, and X = Cl-, NO3-) at 298 +/- 1 K. A considerable increase in adsorption capacity was observed for nitrate counteranions. This process of extraction was followed by the batch method and the order of the maximum capacities found was Ni2+ > Cu2+ > Co2+ for both series of salts. The pendant immobilized groups-cation interaction processes showed exothermic enthalpies. Those values are more pronounced for chlorides, with the largest values obtained for cobalt. The calculated Delta G values are in agreement with the spontaneity of the proposed reactions and the complexation is entropically favored. (C) 2000 Academic Press.2281465

New thiol adsorbent grafted on silica gel: synthesis, characterization and employment for heavy metal adsorptions

Silica gel surface has been modified in two reaction steps: (i) the silylating agent 3-mercaptopropyltrimetox silane was firstly immobilized to give a surface Sil-SH and (ii) this precursor incorporated an ethylene Sulfide molecule to obtain the surface denoted Sil-SSH. This material was characterized by elemental analysis. IR spectroscope. thermogravimetry, solid state and C-13 and Si-29 NMR, and surface area measurement. These materials were employed as adsorbents for divalent heavy cations from aqueous Solutions at room temperature and the isotherms were adjusted to a modified Langmuir equation. The maxima number of moles adsorbed were 1.0, 1.5, 1.6, 2.2, 2.4 and 3.1 mmol g(-1) for Co, Cu, Ni, Cd, Pb. and Hg, respectively.o TEXTO COMPLETO DESTE ARTIGO, ESTARÁ DISPONÍVEL À PARTIR DE AGOSTO DE 2015.5236637

Thioglycolic acid grafted onto silica gel and its properties in relation to extracting cations from ethanolic solution determined by calorimetric technique

Thioglycolic acid was immobilized onto silica gel surface using 3-aminopropyltrimethoxysilane as precursor silylating agent to yield silica. The amount of thioglycolic acid immobilized was 1.03 mmol per gram of silica. This new surface displayed a chelating moiety containing nitrogen, sulfur, and oxygen basic centers which are potentially capable of extracting cations from ethanolic solution, such as MCl3 (M = Fe, Cr, and Mo). This process of extraction was carried out by the batch method when similar chemisorption isotherms were observed for all cations. The data were adjusted to a modified Langmuir equation. The sequence of the maximum retention capacity was Cr(III) > Mo(III) > Fe(III). The same adsorption was determined by calorimetric titration and the enthalpic values of -35.75 +/- 0.02, 32.90 +/- 0.15, and -84.08 +/- 0.12 kJ mol(-1) for chromium, molybdenum, and iron, respectively, were obtained. From the calculated Gibbs free energy -23.4 +/- 0.2, -27.2 +/- 0.2, and -32.7 +/- 0.3 kJ mol(-1), the variations in entropy obtained were 42 +/- 1, 201 +/- 1, and 172 +/- 1 J K-1 mol(-1) for the same sequence. All thermodynamic values are in agreement with the spontaneity of the proposed cation-basic center interactions for these chelating processes. (C) 2004 Elsevier Inc. All rights reserved.273121121

Chemisorption and thermodynamic data of the interaction between a chelate free acidic center with basic groups attached to grafted silicas

The molecule 2-aminoethanethiol was added to the grafted silylant agent [(3-chlorosilylpropyl)trimethoxysilane] (cpts) onto silica gel(dropSil-Cl), obtaining a surface (dropSil-SNH2) and giving 0.70 mmol g(-1) of nitrogen; the surface of silica was modified with [(3-mercaptosilylpropyl)trimethoxysilane] (mpts) with surface (dropSil-SH), giving 0.78 mmol g(-1) of sulphur. Both matrices, (dropSil-SNH2) and (dropSil-SH), adsorb copper and cobalt acetylacetonates from ethanolic solution. Adsorption, using a batch-wise process, showed that copper chelate was the most adsorbed. The interactions between the basic centers attached to organic chains of these modified silicas with the cations in the chelates Me(acac)(2) [M = Cu and Co] were followed through calorimetric titrations. Exothermic enthalpic results were obtained for the dropSil-SNH2 matrix. The spontaneity of these systems was reflected in negative free Gibbs energy and positive from entropic values. (C) 2002 Elsevier Science (USA).249229029

Vermiculite as a useful host for guest cyclic aliphatic amine intercalation, followed by cation adsorption

Two vermiculite hybrids containing aliphatic amines intercalated were synthesized. The amount of guest molecules intercalated resulted in 0.60 and 0.52 mmol g(-1) for pyperidine and pyperazine, respectively, which reflect the effectiveness of such kind of reactions. The processes were confirmed by elemental analysis and infrared spectroscopy. X-ray diffraction patterns suggested that the original crystallinity of matrix was maintained, however, the intercalation process is associated with the conformation of the guest molecule and the presence of the compensate cation inside the interlayer cavity. The intercalated inorganic hosts adsorb divalent lead, nickel, copper and cobalt cations, more effectively at basic pH value, from aqueous solution, which content of adsorption is higher than the precursor native vermiculite. (c) 2006 Elsevier B,V. All rights reserved.28041699394

Synthesis of modified vermiculite by interaction with aromatic heterocyclic amines

Vermiculite of general formula [Si6.85Al1.15][Mg4.68Al0.51Fe0.63]O-20(OH)(4)Ca0.128Na0.032K0.094 reacted with heteroaromatic amines alpha-, beta-, and gamma-picolines from aqueous solution. The products were characterized by elemental analysis, infrared spectroscopy, and X-ray diffraction. The intercalated nanocompounds maintained the crystallinity and changed the original interlayer distance of 1422pm to 1474, 1456, and 1474 pm, for the sequence of the guest picoline molecules. Natural and intercalated vermiculite can remove copper at the solid/liquid interface; removal 0.40 mmol g(-1) was obtained for the original matrix, and 1.10, 0.92, and 1.33 mmol g(-1) for the intercalated forms. These values are near the capacity of cation exchange (CEC) of this clay mineral, which can be possibly used as source of copper removal from aqueous solution. (c) 2006 Elsevier Ltd. All rights reserved.6781835184

Picoline as ligand with antimony trichloride and triiodide adducts

Solid adducts SbX3.L-pic (X=Cl, I and L=alpha-, beta- and gamma-picolines) were synthesized and characterized by elemental analysis, H-1 and C-13 NMR, IR spectroscopy and thermal analysis. ne infrared spectroscopy and the magnetic resonance for H-1 and C-13 nuclei of these compounds suggest that the ligands coordinate through nitrogen atom. Kinetic studies were accomplished by means of thermogravimetric data, through isothermal and non-isothermal techniques. The best adjusting models for adducts thermal decomposition were R-1 for isothermal and R-1 and R-2 for the non-isothermal methods. The energy of activation values obtained by isothermal method indicate the following orders of thermal stability for adducts: i) SbCl3.alpha-pic>SbCl3.beta-pic>SbCl3.gamma-pic and ii) SbI3.beta-pic<SbI3&BULL;&gamma;-pic<SbI3.alpha-pic. The activation energy values obtained by non-isothermal were higher than those from isothermal methods, showing the order of stability: iii) SbCl3.alpha-pic<SbCl3&BULL;&beta;-pic<SbCl3.gamma-pic and iv) SbI3.beta-pic<SbI3&BULL;&alpha;-pic&CONG;SbI3&BULL;&gamma;-pic. These obtained data through R, model presented the kinetic compensation effect for trichloride adducts, which could be associated to both isothermal and non-isothermal processes.75397598