The role of variable surface charge and surface complexation in the adsorption of humic acid on magnetite

Illés, Erzsébet; Tombácz, Etelka

doi:10.1016/j.colsurfa.2003.09.017

Cited by 218 publications

(173 citation statements)

References 29 publications

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“…The pH-dependent surface charge density was characterized quantitatively in potentiometric acid-base titration experiments. 31 The pH of PZC (point of zero charge) of the synthesized magnetite is 7.9 ±0.1.…”

Section: Methodsmentioning

confidence: 99%

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Mechanism of in Situ Surface Polymerization of Gallic Acid in an Environmental-Inspired Preparation of Carboxylated Core–Shell Magnetite Nanoparticles

et al. 2014

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Corresponding authorsM. Szekeres (szekeres@chem.u-szeged.hu) and E. Tombácz (tombacz@chem.u-szeged.hu) Graphical abstract AbstractMagnetite nanoparticles (MNPs) with biocompatible coatings are good candidates for MRI (magnetic resonance imaging) contrasting, magnetic hyperthermia treatments and drug delivery systems. The spontaneous surface induced polymerization of dissolved organic matter on environmental mineral particles inspired us to prepare carboxylated core-shell MNPs by using a ubiquitous polyphenolic precursor. Through the adsorption and in-situ surface polymerization of gallic acid (GA), a polygallate (PGA) coating is formed on the nanoparticles (PGA@MNP) with possible antioxidant capacity. The Polygallate on magnetite nanoparticles Humic matter on clays 2This is a PDF file of an unedited manuscript that has been accepted for publication. Final edited form is published in Langmuir, 2014, 30:15451−15461. http://dx.doi.org/10.1021/la5038102 present work explores the mechanism of polymerization with the help of potentiometric acid-base titration, dynamic light scattering (for particle size and zeta potential determination), UV-Vis (UVvisible light spectroscopy), FTIR-ATR (Fourier-transformed infrared spectroscopy by attenuated total reflection) and XPS (X-ray photoelectron spectroscopy) techniques. We observed the formation of ester and ether linkages between gallate monomers both in solution and in the adsorbed state. Higher polymers were formed in the course of several weeks both on the surface of nanoparticles and in the dispersion medium. The ratio of the absorbances of PGA supernatants at 400 and 600 nm (i.e., the E4/E6 ratio commonly used to characterize the degree of polymerization of humic materials) was determined to be 4.3, similar to that of humic acids. Combined XPS, dynamic light scattering and FTIR-ATR results revealed that prior to polymerization, the GA monomers became oxidized to polycarboxylic acids due to ring opening while Fe 3+ ions reduced to Fe 2+ . Our published results on the colloidal and chemical stability of PGA@MNPs are referenced thoroughly in the present work. Detailed studies on biocompatibility, antioxidant property and biomedical applicability of the particles will be published.

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Section: Methodsmentioning

confidence: 99%

“…[29][30][31] Concentrated iron salt solutions (FeCl2·4H2O and FeCl3·6H2O, Molar, Hungary) were mixed at the ratio of iron(II) to iron(III) 1:2 and filtered into fresh ultrapure water using a microfilter (0.2 μm). Freshly prepared NaOH solution was added to the iron salt solution under rigorous stirring.…”

Section: Methodsmentioning

confidence: 99%

Mechanism of in Situ Surface Polymerization of Gallic Acid in an Environmental-Inspired Preparation of Carboxylated Core–Shell Magnetite Nanoparticles

et al. 2014

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“…We compared the effect of the adsorption of the different organic acids on the pH-dependent charging, salt tolerance and so the colloidal stability of magnetite nanoparticles. Some of the results used here can be found in our earlier publications [6][7][8][9]16], together with the detailed discussions on the mechanisms of adsorption. Therefore, we do not intend to go into those details, but we use our earlier conclusions to support the findings of the present comparative study on the stabilizing efficiencies of small and large molecular organic acids.…”

Section: Introductionmentioning

confidence: 99%

“…HA is able to form appropriate stabilizing layer on metal oxide particles due to its specific affinity to metal ions and polyionic character [4,5]. Besides our several years' experience with aqueous solutions of humic acids, their interaction with magnetite (Fe3O4, magnetic iron oxide) has been also studied [6,7]. The CA, PAA and PAM interactions with magnetite nanoparticles have been recently investigated [8,9,16].…”

Section: Introductionmentioning

confidence: 99%

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Adsorption of organic acids on magnetite nanoparticles, pH-dependent colloidal stability and salt tolerance

Tombácz

Tóth

Nesztor

et al. 2013

Colloids and Surfaces A: Physicochemical and Engineering Aspect

115

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Graphical abstractH-type isotherms HA, PAM, GA, and CA Highlights  Organic acids either stabilize or destabilize oxide nanoparticles in natural waters.  The stabilizing/destabilizing effect depends on pH, salinity and organic concentration.  Specific configuration of carboxylic groups is necessary to surface complexation.  Surface complexation leads to high affinity adsorption isotherms.  Higher molecular weight organic acids provide better stability than smaller ones. AbstractThe adsorption of different organic acids and their influence on the pH-dependent charging, salt tolerance and so the colloidal stability of magnetite nanoparticles are compared. Adsorption isotherms of citric acid -CA, gallic acid -GA, poly(acrylic acid) -PAA, poly(acrylic-co-maleic acid) -PAM and humic acid -HA were measured. The pH-dependent charge state of MNPs was characterized by electrophoretic mobility and their aggregation by dynamic light scattering. The salt tolerance was tested in coagulation kinetic experiments. Although the adsorption capacities, the type of bonding (either H-bonds or metal ioncarboxylate complexes) and so the bond strengths are significantly different, the following general trends have been found. Small amount of organic acids at pH < ~8 (the pH of PZC of magnetite) -relevant condition in natural waters -only neutralizes the positive charges, and so promotes the aggregation and sedimentation of nanoparticles. Greater amounts of organic acid, above the charge neutralization, cause the sign reversal of particle charge, and at high

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Organo‐Clay Complexes in Soils and Sediments

Chilom

Rice

2009

Biophysico‐Chemical Processes Involving Natural Nonliving Organic Matter in Environmental Systems

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The role of variable surface charge and surface complexation in the adsorption of humic acid on magnetite

Cited by 218 publications

References 29 publications

Mechanism of in Situ Surface Polymerization of Gallic Acid in an Environmental-Inspired Preparation of Carboxylated Core–Shell Magnetite Nanoparticles

Mechanism of in Situ Surface Polymerization of Gallic Acid in an Environmental-Inspired Preparation of Carboxylated Core–Shell Magnetite Nanoparticles

Adsorption of organic acids on magnetite nanoparticles, pH-dependent colloidal stability and salt tolerance

Organo‐Clay Complexes in Soils and Sediments

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