The effect of humic acid adsorption on pH-dependent surface charging and aggregation of magnetite nanoparticles

Research output: Contribution to journalArticle

362 Citations (Scopus)

Abstract

The pH-dependent adsorption of humic acid (HA) on magnetite and its effect on the surface charging and the aggregation of oxide particles were investigated. HA was extracted from brown coal. Synthetic magnetite was prepared by alkaline hydrolysis of iron(II) and iron(III) salts. The pH-dependent particle charge and aggregation, and coagulation kinetics at pH∼4 were measured by laser Doppler electrophoresis and dynamic light scattering. The charge of pure magnetite reverses from positive to negative at pH∼8, which may consider as isoelectric point (IEP). Near this pH, large aggregates form, while stable sols exist further from it. In the presence of increasing HA loading, the IEP shifts to lower pH, then at higher loading, magnetite becomes negatively charged even at low pHs, which indicate the neutralization and gradual recharging positive charges on surface. In acidic region, the trace HA amounts are adsorbed on magnetite surface as oppositely charged patches, systems become highly unstable due to heterocoagulation. Above the adsorption saturation, however, the nanoparticles are stabilized in a way of combined steric and electrostatic effects. The HA coated magnetite particles form stable colloidal dispersion, particle aggregation does not occur in a wide range of pH and salt tolerance is enhanced.

Original languageEnglish
Pages (from-to)115-123
Number of pages9
JournalJournal of Colloid and Interface Science
Volume295
Issue number1
DOIs
Publication statusPublished - Mar 1 2006

Fingerprint

Magnetite Nanoparticles
Ferrosoferric Oxide
Magnetite nanoparticles
Humic Substances
Magnetite
magnetite
charging
Agglomeration
Adsorption
nanoparticles
acids
adsorption
Iron
Salts
recharging
salts
iron
Coal
Lignite
Polymethyl Methacrylate

Keywords

  • Adsorption
  • Aggregation
  • Colloidal stability
  • Heterocoagulation
  • Humic acid
  • Iron oxide
  • Magnetic separation
  • Magnetite
  • Surface modification

ASJC Scopus subject areas

  • Colloid and Surface Chemistry
  • Physical and Theoretical Chemistry
  • Surfaces and Interfaces

Cite this

@article{14328a4ff91742a6b95e152e2a69ea5b,
title = "The effect of humic acid adsorption on pH-dependent surface charging and aggregation of magnetite nanoparticles",
abstract = "The pH-dependent adsorption of humic acid (HA) on magnetite and its effect on the surface charging and the aggregation of oxide particles were investigated. HA was extracted from brown coal. Synthetic magnetite was prepared by alkaline hydrolysis of iron(II) and iron(III) salts. The pH-dependent particle charge and aggregation, and coagulation kinetics at pH∼4 were measured by laser Doppler electrophoresis and dynamic light scattering. The charge of pure magnetite reverses from positive to negative at pH∼8, which may consider as isoelectric point (IEP). Near this pH, large aggregates form, while stable sols exist further from it. In the presence of increasing HA loading, the IEP shifts to lower pH, then at higher loading, magnetite becomes negatively charged even at low pHs, which indicate the neutralization and gradual recharging positive charges on surface. In acidic region, the trace HA amounts are adsorbed on magnetite surface as oppositely charged patches, systems become highly unstable due to heterocoagulation. Above the adsorption saturation, however, the nanoparticles are stabilized in a way of combined steric and electrostatic effects. The HA coated magnetite particles form stable colloidal dispersion, particle aggregation does not occur in a wide range of pH and salt tolerance is enhanced.",
keywords = "Adsorption, Aggregation, Colloidal stability, Heterocoagulation, Humic acid, Iron oxide, Magnetic separation, Magnetite, Surface modification",
author = "E. Ill{\'e}s and E. Tomb{\'a}cz",
year = "2006",
month = "3",
day = "1",
doi = "10.1016/j.jcis.2005.08.003",
language = "English",
volume = "295",
pages = "115--123",
journal = "Journal of Colloid and Interface Science",
issn = "0021-9797",
publisher = "Academic Press Inc.",
number = "1",

}

TY - JOUR

T1 - The effect of humic acid adsorption on pH-dependent surface charging and aggregation of magnetite nanoparticles

AU - Illés, E.

AU - Tombácz, E.

PY - 2006/3/1

Y1 - 2006/3/1

N2 - The pH-dependent adsorption of humic acid (HA) on magnetite and its effect on the surface charging and the aggregation of oxide particles were investigated. HA was extracted from brown coal. Synthetic magnetite was prepared by alkaline hydrolysis of iron(II) and iron(III) salts. The pH-dependent particle charge and aggregation, and coagulation kinetics at pH∼4 were measured by laser Doppler electrophoresis and dynamic light scattering. The charge of pure magnetite reverses from positive to negative at pH∼8, which may consider as isoelectric point (IEP). Near this pH, large aggregates form, while stable sols exist further from it. In the presence of increasing HA loading, the IEP shifts to lower pH, then at higher loading, magnetite becomes negatively charged even at low pHs, which indicate the neutralization and gradual recharging positive charges on surface. In acidic region, the trace HA amounts are adsorbed on magnetite surface as oppositely charged patches, systems become highly unstable due to heterocoagulation. Above the adsorption saturation, however, the nanoparticles are stabilized in a way of combined steric and electrostatic effects. The HA coated magnetite particles form stable colloidal dispersion, particle aggregation does not occur in a wide range of pH and salt tolerance is enhanced.

AB - The pH-dependent adsorption of humic acid (HA) on magnetite and its effect on the surface charging and the aggregation of oxide particles were investigated. HA was extracted from brown coal. Synthetic magnetite was prepared by alkaline hydrolysis of iron(II) and iron(III) salts. The pH-dependent particle charge and aggregation, and coagulation kinetics at pH∼4 were measured by laser Doppler electrophoresis and dynamic light scattering. The charge of pure magnetite reverses from positive to negative at pH∼8, which may consider as isoelectric point (IEP). Near this pH, large aggregates form, while stable sols exist further from it. In the presence of increasing HA loading, the IEP shifts to lower pH, then at higher loading, magnetite becomes negatively charged even at low pHs, which indicate the neutralization and gradual recharging positive charges on surface. In acidic region, the trace HA amounts are adsorbed on magnetite surface as oppositely charged patches, systems become highly unstable due to heterocoagulation. Above the adsorption saturation, however, the nanoparticles are stabilized in a way of combined steric and electrostatic effects. The HA coated magnetite particles form stable colloidal dispersion, particle aggregation does not occur in a wide range of pH and salt tolerance is enhanced.

KW - Adsorption

KW - Aggregation

KW - Colloidal stability

KW - Heterocoagulation

KW - Humic acid

KW - Iron oxide

KW - Magnetic separation

KW - Magnetite

KW - Surface modification

UR - http://www.scopus.com/inward/record.url?scp=28544452029&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=28544452029&partnerID=8YFLogxK

U2 - 10.1016/j.jcis.2005.08.003

DO - 10.1016/j.jcis.2005.08.003

M3 - Article

C2 - 16139290

AN - SCOPUS:28544452029

VL - 295

SP - 115

EP - 123

JO - Journal of Colloid and Interface Science

JF - Journal of Colloid and Interface Science

SN - 0021-9797

IS - 1

ER -