Ethyleneimine Anchored on Thiol-Modified Silica Gel Surface—Adsorption of Divalent Cations and Calorimetric Data

Arakaki, Luiza N.H.; Nunes, Liliane M.; Simoni, Jane M.; Airoldi, Cláudio

doi:10.1006/jcis.2000.6842

Cited by 55 publications

(43 citation statements)

References 32 publications

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“…The expected distribution of pendant groups incorporating basic centers on modified surfaces, are potentially available as complexing moieties to adsorb metallic chelates, in which the acidic centers are located on divalent copper or cobalt in the form of bis-acetylacetonates (acac) in ethanolic solution (11)(12)(13)(14)(15)(16). Results of the adsorption of those cations on modified surfaces are presented in the Table 1, which were quantified through the isos- therms shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…In the present work, we investigated the chemisorption and focused on thermodynamic determination upon and interaction of copper and cobalt acetylacetonate chelates with modified silica gel, after grafting with silylant agent [(3-mercaptopropyl) trimethoxysilane], (≡Sil-SH), and the matrix (≡Sil-Cl) modified with a 2-aminoethanethiol molecule, (≡Sil-SNH 2 ).These modified silicas were previously investigated in an attempt to explore their capacities for adsorbing transitions metal cations, which have the counter anion chloride and nitrate, in a process performed in aqueous and nonaqueous media (14,16,20,21). But, lack of thermodynamic data of these studied surfaces, concerning the β-diketonates complexes not yet reported in the literature, justifies such determinations in the present work.…”

Section: Introductionmentioning

confidence: 99%

“…The resultant modified surfaces can be applied to many areas, such as catalysis and chromatography, and it can serve as a sequestrant agent for cations (15)(16)(17), an ion-exchanger (18), as analytes for electroanalytical purposes (19), and in effluent waste removal from industrial processes (7).…”

Section: Introductionmentioning

confidence: 99%

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Chemisorption and Thermodynamic Data of the Interaction between a Chelate Free Acidic Center with Basic Groups Attached to Grafted Silicas

Arakaki

Sousa

Espı́nola

et al. 2002

Journal of Colloid and Interface Science

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Chemisorption and Thermodynamic Data of the Interaction between a Chelate Free Acidic Center with Basic Groups Attached to Grafted Silicas

Arakaki

Sousa

Espı́nola

et al. 2002

Journal of Colloid and Interface Science

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“…The large surface area and pore volume of silica underlie facile adsorption and high loading effect of various chelating agents (Trewyn et al 2007). Silica gel especially immobilized with various organic compounds with metal chelating ability had been widely used (Zaporozhets et al 1999), because this support offers pronounced advantages over other organic/inorganic support (Arakaki et al 2000). The application of silica is attributed to the presence of high number of reactive hydroxylic groups on its surface.…”

Section: Introductionmentioning

confidence: 99%

Derived and thiourea-functionalized silica for cadmium removal: isotherm, kinetic and thermodynamic studies

2018

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The present study explored the feasibility of using derived and thiourea-functionalized silica as adsorbent for the removal of cadmium under different experimental conditions. Effects of various parameters such as function of point of zero charge (pH PZC ), solution pH, sorbent-sorbate resident time and ratio, concentration and temperature were investigated. The sorption of cadmium followed the pseudo-second-order rate kinetics. Thermodynamic studies revealed that the sorption of cadmium was endothermic and spontaneous, with good affinity toward the sorbent. Various isotherm models, viz. Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Harkins-Jura, and Halsey isotherms were used to analyze the equilibrium data at different temperatures. The Freundlich, Halsey, Langmuir, and Temkin models were found to be in good agreement with the experimental data with high R 2 , low RMSE, and low χ 2 values. The results show that the sorption capacity increases with an increase in solution temperature from 28 to 65 °C. The maximum sorption capacity calculated from Langmuir isotherm was 27.55 and 28.41 mg g −1 for derived and thiourea-functionalized silica, respectively, at optimum condition of pH 5 and contact time of 120 min.

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“…Silica gel does not exhibit the friability and low bulk density of SBA-15 [14][15][16] while the surface properties and stability are similar, and it can be functionalised in the same way. The silica gel used here has been chosen to have an average pore diameter similar to that of SBA-15.…”

Section: Introductionmentioning

confidence: 99%

Environmentally Benign Bifunctional Solid Acid and Base Catalysts

Elmekawy

Shiju

Rothenberg

et al. 2014

Ind. Eng. Chem. Res.

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ABSTRACT:Solid bi-functional acid-base catalysts were prepared in two ways on an amorphous silica support: 1) by grafting mercaptopropyl units (followed by oxidation to propylsulfonic acid) and aminopropyl groups to the silica surface (NH 2 -SiO 2 -SO 3 H), and 2) by grafting only aminopropyl groups and then partially neutralising with phosphotungstic acid, relying on the H 2 PW 12 O 40 -ion for surface acidity (NH 2 -SiO 2 -NH 3 + [H 2 PW 12 O 40 -], denoted as NH 2 -SiO 2 -PTA).Surface acidity and basicity were characterised by adsorption calorimetry, using SO 2 as a probe for surface basicity and NH 3 for surface acidity. Catalytic activities were compared in a two-stage cascade: an acid-catalysed deacetalisation followed directly by a base-catalysed Henry reaction. Overall, the NH 2 -SiO 2 -SO 3 H catalysts showed higher concentrations and strengths of both acid and base sites, and higher activities than NH 2 -SiO 2 -PTA. Both catalysts showed evidence of cooperative acid-base catalysis. Importantly, the bi-functional catalysts exhibited catalytic advantage over physical mixtures of singly functionalised catalysts. 3 INTRODUCTIONMany liquid phase processes in fine chemicals synthesis require acid or base catalysts. Conventionally, homogeneous acids and bases dissolved in the reaction mixtures are used. In most cases, replacing these with solid acids and bases brings substantial environmental benefit by reducing waste and simplifying product separation. 1-3Almost inevitably, however, solid acids and bases are less active than their homogeneous counterparts. Despite this, one case where they might be able to offer particular advantage is where both acid and base catalysis is required, either in sequential steps or through a cooperative catalytic mechanism. A difficulty associated with preparation of the aminopropyl/propylsulfonic acid bi-functional catalysts (NH 2 -SiO 2 -SO 3 H) is that the acid group is grafted to the silica using (3-mercaptopropyl)trimethoxysilane (MPTMS) and an oxidation step is required to convert the thiol (-SH) to sulfonic acid (-SO 3 H). The two main routes reported are based on hydrogen peroxide/sulfuric acid, and on nitric acid (as both oxidant and acidifier). 11,12 The method used must be chosen to effectively oxidise thiol 12 but with minimal reaction with the base groups. Nitric acid has been shown to be the more effective reagent under these conditions 13 so nitric acid is used as the oxidant in the work reported here.An amorphous silica gel has been used as the catalyst support, rather than the ordered SBA-15 silica used in our previous work. Silica gel does not exhibit the friability and low bulk density of SBA-15 14-16 while the surface properties and stability are similar, and it can be functionalised in the same way. The silica gel used here has been chosen to have an average pore diameter similar to that of SBA-15. The tandem deacetalisation-Henry reaction shown in Scheme 2 has been used. The first step is the acid-catalysed deacetalisation of benzaldehyde dimethyl acetal i...

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Ethyleneimine Anchored on Thiol-Modified Silica Gel Surface—Adsorption of Divalent Cations and Calorimetric Data

Cited by 55 publications

References 32 publications

Chemisorption and Thermodynamic Data of the Interaction between a Chelate Free Acidic Center with Basic Groups Attached to Grafted Silicas

Chemisorption and Thermodynamic Data of the Interaction between a Chelate Free Acidic Center with Basic Groups Attached to Grafted Silicas

Derived and thiourea-functionalized silica for cadmium removal: isotherm, kinetic and thermodynamic studies

Environmentally Benign Bifunctional Solid Acid and Base Catalysts

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