Interfacial and rheological properties of humic acid/hematite suspensions

Ramos-Tejada, María del Mar; Ontiveros-Ortega, A.; Viota, J.L.; Durán, J.D.G.

doi:10.1016/s0021-9797(03)00665-9

Cited by 75 publications

(49 citation statements)

References 31 publications

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“…Particles become covered completely by a further increase in humate concentration inducing the dispersion of aggregated particles. The electrostatic interaction between the positively charged iron oxide and the organic polyanions is significant under hardly acidic conditions [5,9], the formation of surface complexes is enhanced by local electrostatic field.…”

Section: Humate and Citrate Adsorption On Magnetite Nanoparticlesmentioning

confidence: 99%

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Surface charging, polyanionic coating and colloid stability of magnetite nanoparticles

Hajdú

Illés

Tombácz

et al. 2009

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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a b s t r a c tThe formation of small and large molecular polyanionic coating on the surface of magnetite (Fe 3 O 4 ) nanoparticles and their role in the stability enhancement of aqueous magnetic fluids are compared. Magnetite was synthesized and stabilized with citric (CA) and humic (HA) acids. The macromolecular HA, a notable fraction of the natural organic matter (NOM), contains mainly carboxylic groups similarly to the CA, and both acids are able to form surface complexes on the ≡Fe-OH sites of iron oxides. The pHdependent charge state of particles and their aggregation were quantified, and the enhanced salt tolerance of stabilized systems was studied. The dynamic light scattering (DLS) method was used to characterize colloidal stability under different conditions. The average particle size and electrophoretic mobility were measured, and the electrolyte tolerance was tested in coagulation kinetic measurements. The colloidal stability of magnetite dispersions depends sensitively on the pH and the concentration of organic acids present. The trace amount of HA neutralizes the positive charges on magnetite surface under acidic condition only in part, and so it promotes the aggregation between the particles having both positive sites and negative humate patches on the surface. Above the adsorption saturation, the surface becomes completely covered causing the reversal of charge sign and overcharging of nanoparticles. The magnetite nanoparticles become stabilized in a way of combined steric and electrostatic effects. The thicker layer of macromolecular HA provides better electrosteric stability than that of CA coating. However, in the presence of either CA or HA, the dissolution of magnetite is enhanced due to the complexation of iron ions in the aqueous medium.

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Section: Humate and Citrate Adsorption On Magnetite Nanoparticlesmentioning

confidence: 99%

“…The coverage of particles with adsorption layer provides enhanced resistance against the particle aggregation. In aqueous medium, electrostatic, steric or combined stabilization layers can develop [3,8,9]. The thicker coating provides better stability [10].…”

Section: Introductionmentioning

confidence: 99%

Surface charging, polyanionic coating and colloid stability of magnetite nanoparticles

Hajdú

Illés

Tombácz

et al. 2009

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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“…They have a potentially long useful life of about 5 years or more with proper care and maintenance [13]. One of the most important properties of clay is its rheological properties which are a function of pH of solution, structure, particle size, shape, and surface characteristics of the dispersed phase [14]. Controlling the rheological property of clay is often indispensable in industrial processes and practical applications involving ceramics processing (meltprocessing behavior such as injection molding) or paper coating [15].…”

Section: Introductionmentioning

confidence: 99%

Performance Evaluation of Clay-Sawdust Composite Filter for Point of Use Water Treatment

Nnaji¹,

Afangideh²,

Ezeh³

2016

Nig. J. Tech.

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Water borne diseases have remained a major challenge in most developing countries. This is usually as a result of lack of access to clean water and contamination associated with water fetching and conveyance. This work explores the possibility of improving water quality and eliminating the possibility of recontamination by the use of point of use (POU) water filters made from cheap locally available materials. The performance of POU water filters for the purification of water obtained from various sources was investigated. Sawdust was used as a burnout material in order to enhance the rate of filtration. The clay was first characterized and then various proportions (5%, 10%, 20%, 30% and 50% by weight) of sawdust were mixed with the clay for filter production. The clay was found to have a specific gravity of 2.4, a high liquid limit of 81.6% and a medium plastic limit of 48.54%. The flow rates of the filters ranged between 0.0005litres/hr for the filter with 5% sawdust and 0.8litres/hr for the filter with 50% sawdust. The average removal of suspended solids (SS) and biochemical oxygen demand (BOD) was 98.6% and 33% respectively while the mean Log10 reduction in total count (TC) was 93.1%. Result of analysis of variance showed that there was no significant difference between the performances of the filters. However, there was a significant difference between the flow rates with F(18.71) > F critical (5.14). This implies that while burnout materials improve water quality, increasing burnout materials in clay filters beyond 50% does not significantly affect the performance for the filter with respect to the quality of effluent but with respect to flow rate.

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“…The coverage of particles with adsorption layer provides enhanced resistance against the particle aggregation. In aqueous medium, electrostatic, steric or combined (i.e., electrosteric) stabilization layers can develop [5,12,13]. The thicker coating provides better stability [14].…”

Section: Introductionmentioning

confidence: 99%

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

111

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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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Interfacial and rheological properties of humic acid/hematite suspensions

Cited by 75 publications

References 31 publications

Surface charging, polyanionic coating and colloid stability of magnetite nanoparticles

Surface charging, polyanionic coating and colloid stability of magnetite nanoparticles

Performance Evaluation of Clay-Sawdust Composite Filter for Point of Use Water Treatment

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

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