Constrained growth of anisotropic magnetic δ-FeOOH nanoparticles in the presence of humic substances

Abstract

Natural polyelectrolytes, humic substances, are suggested to control in situ growth of feroxyhyte nanoparticles of a highly reduced mean size and with enhanced colloidal stability in salt solutions. The feroxyhyte is formed as 2-5 nm thick and 20 6 20 nm wide nanoflakes due to the blocking of developing facets of feroxyhyte and constraints caused by diffusion limitations of ionic constituents across partially charged branches of humic substances. ExperimentalHigh-purity FeCl 2 ?4H 2 O was purchased from ABCR GmbH&Co (Germany). Potassium humate was purchased from ''Sakhalinsky Humates'' (groups of companies, Russia). According to manufacturer's information, potassium humate was produced by alkaline extraction from leonardite.

Humic acid-stabilized superparamagnetic maghemite nanoparticles: surface charge and embryotoxicity evaluation

“…Note that the nanoparticle sizes calculated from TEM images (2 -5 nm; 3.5 ± 0.8 nm mean size) are significantly below the hydrodynamic diameter (145 ± 60 nm) reported for the same SPION-HA colloids elsewhere [6]. This supports the previous hypothesis that SPIONs not only adsorb the humic substances but also penetrate into the branched structure of the conglomerates of humic acid molecules and become assembled there [6,7]. A simplified illustration of this process is given on Fig.…”

“…It was previously demonstrated that the humic acids (HA), i.e. the natural organic matter originating from biochemical and microbiological transformations of organic materials under environmental conditions, can efficiently stabilize iron oxide nanoparticles due to the numerous highly developed branches with irregularly located organic functional groups [6][7][8][9][10][11]. However, the colloidal stability of the resulting core-shell organic-inorganic nanomaterials at different pH values was not characterized, while it is crucial for biomedical applications of the stabilized SPIONs.…”

Microwave-Assisted Synthesis of Water-Dispersible Humate-Coated Magnetite Nanoparticles: Relation of Coating Process Parameters to the Properties of Nanoparticles

“…The samples MW-HS-1, MW-HS-2, MW-HS-3 were prepared via microwave-assisted synthesis in a microwave oven (Midea AW925EHU) equipped with an overhead stirrer using potassium humate (110 mg) as a capping agent preliminarily dissolved in 40 mL of distilled water also by the above described procedure. A wide range of humic substances concentrations was used in the synthesis of nanoparticles, which vary from 0.1 to 3.3 g L -1 [28,32]. Also, there is no consensus on the ratio of NPs/HSs, which, evidently, depends on the surface area of stabilizing materials and chemical composition of HSs.…”

“…In the literature, one can find reports on using HSs as a stabilizer for nanoparticles of metals [26,27] and oxides [28][29][30][31][32]. However, their use is not only limited to preventing aggregation of nanoparticles but it is suggested that derivatives of humic acid could play a role of a functional component, for example, in processes of water cleaning from heavy metals [33,34] and organic contaminants [35,36].…”

Synthesis and characterization of hybrid materials containing iron oxide for removal of sulfides from water

“…In the case of CM3, this component is characterized by a much stronger effect than in the case of CG3. Moreover, in the spectrum of hybrid polymer CM3 there appears one more quadruple doublet with parameters QS = 3.01 mm/s and IS = 1.35 mm/s, originating from the high-spin atoms of Fe(II), which may indicate the presence of Fe(OH) 2[22]. The significant difference in the effects in the spectra of the products based on the carboxylic cation exchangers CM3 and CG3 with a similar Fe(III) content (about 30%) may indicate a looser structure of the crystal lattice of the iron oxides deposited in the matrix of the gel cation exchanger than the one in the matrix of the macroporous cation exchanger.…”