Adhesion of Colloidal Hematite onto Mercury in Water–Ethanol Media

Andrade, Estela Marı́a; Molina, Fernando V.; Posadas, D.

doi:10.1006/jcis.1999.6243

Cited by 5 publications

(2 citation statements)

References 40 publications

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“…where ε 1 (0) represents the static dielectric constant(ε 1 (0) ) 12.0), n 1 is the refractive index (n 1 2 ) 9.3025), and ω 1UV is the UV absorption frequencies of hematite (ω 1UV ) 0.346 × 10 16 rad.s -1 ) (22). ε w (0) corresponds to the static dielectric constant (ε w (0) ) 78.54) and n w is the refractive index (n w 2 ) 1.755) of water (23), h p is the Planck constant (6.63 × 10 -34 J • s).…”

Section: Methodsmentioning

confidence: 99%

Modeling the Adsorption and Coagulation of Fulvic Acids on Colloids by Brownian Dynamics Simulations

Seijo

Ulrich

Filella

et al. 2009

Environ. Sci. Technol.

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Humic substances (HS) play an important role in the reactivity and transport of colloids in natural environments. In particular, the presence of fulvic acids (FA) in natural waters modifies the interactions between inorganic particles and biopolymers and makes difficult to predict their stability with regard to aggregation processes. In this study, Brownian dynamics (BD) modeling is applied to quantify the interactions between negatively charged FA and (i) a positively charged inorganic particle and (ii) a rigid neutral polysaccharide in aqueous solutions. Hematite and schizophyllan are respectively used as model colloids. Modeling the adsorption of FA at the hematite particle surface and on the polysaccharide is based on van der Waals attractive forces and electrostatic interactions. Possible applications of the model, however, are not restricted to this system and any interaction potential or colloidal particle can be considered. The competition between FA adsorption and FA homocoagulation in solution is studied as function of the solution ionic strength. Results show that, under the conditions used, the amount of adsorbed FA is largely controlled by the solution ionic strength. At low ionic strength the amount of adsorbed FA is limited by the electrostatic repulsion between FA at the colloid surfaces and FA monolayers are formed. By increasing the ionic strength the number of adsorbed FA is found to increase. At a sufficiently large ionic strength, however, FA coagulation in solution may strongly compete with FA adsorption at the hematite and polysaccharide surfaces. FA aggregates then adsorb at the colloid surfaces to form extended and porous structures. Results also suggest that FA adsorption and structure of the adsorbed layers are mainly driven by the complex interplay between electrostatic attractive and repulsive interactions.

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Section: Methodsmentioning

confidence: 99%

Modeling the Adsorption and Coagulation of Fulvic Acids on Colloids by Brownian Dynamics Simulations

Seijo

Ulrich

Filella

et al. 2009

Environ. Sci. Technol.

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“…The colloidal nanosized -Fe 2 O 3 has wide potential applications such as the environmental remediation [1,2], medicine [3], photoelectrolysis reactor [4][5][6][7][8], fundamental research of colloidal science [9][10][11][12][13], nanofluid [14], coating, and printing application [15]. Up to now, various physical and chemical processes, such as ball milling [16,17], coprecipitation [18,19], sol-gel method [20], micelle template [21], hydrothermal methods [22][23][24][25][26][27][28][29][30][31][32], the solution combustion synthesis technique [33,34], the forced hydrolysis of Fe(III) solution [35][36][37], microwave-assisted method [38,39], and pyrolysis of iron organic complexes [40], have been reported for the preparation of the nanoscaled -Fe 2 O 3 with different forms and morphologies.…”

Section: Introductionmentioning

confidence: 99%

Preparation and Characterization of Nanosized Hematite Colloids Using Green Vitriol as Ferrum Source

Chen

Cao

et al. 2014

Journal of Nanomaterials

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The paper reports a green synthetic route for nanosized hematite colloids with an excellent monodispersity, using green vitriol and ammonia as raw materials. The reaction conditions of the synthetic route were studied and the as-prepared samples were characterized by XRD, TEM, TG-DTA, DLS, and XPS. The results indicated that the key factors for the monodispersity of the colloidal product were preheating reactants and washing repeatedly the intermediate Fe(OH)3. When the initial pH was set as 4 or 5, the transformation product of Fe(OH)3was the pureα-Fe2O3with the minim adsorptive sulfate ions. Contrarily, the mixtures ofα-Fe2O3andα-FeOOH were obtained at the pH 6 or 7, which were related to the mechanism of transformation reaction. In addition, the concentration of Fe(OH)3should be less than or equal to 0.2 mol/L in order to prepare the qualified nanosized hematite colloids. The researches proved that the excellent monodispersity of the colloidal product resulted from a fine dispersion state of the synthetic system during the whole process and that it was a significant way to obtain the nanosized metallic oxide colloids from the corresponding metal hydroxide due to avoidance of hyperspeed centrifugal separation or dialysis operation.

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