Phosphate adsorption at variable charge soil/water interfaces as influenced by ionic strength

The effect of phosphate adsorption on zeta potential of the colloids of variable charge soils and the effect of ionic strength on phosphate adsorption by the soils were investigated using batch experimental method. The presence of phosphate resulted in the decrease in zeta potential and isoelectric point (IEP) of the colloids of the soils, which further suggested that the phosphate was adsorbed specifically by these soils. The effect of phosphate adsorption on zeta potential was correlated with the content of free Fe/Al oxides in the soils; the higher the content of Fe/Al oxides in a soil the greater was the decrease in zeta potential and IEP of the soil colloids. The intersection of phosphate adsorption–pH curves at different ionic strengths (a characteristic pH) was obtained for 2 Oxisols. Above this pH, the adsorption of phosphate increased with increasing ionic strength, whereas below it the reverse trend occurred. The intersect pH was 4.60 for the Oxisol from Guangdong and 4.55 for the Oxisol from Yunnan, which was lower than the values of PZSE (point of zero salt effect) of these soils, but near the PZNC (point of zero net charge) of the soils. The effects of ionic strength and pH on phosphate adsorption by these soils were interpreted with the help of an adsorption model developed previously by Bowden et al. The results of zeta potential suggested that the potential in an adsorption plane became less negative with increasing ionic strength above the soil PZNC and decreased with increasing ionic strength below the soil PZNC. These results support the hypothesis of the adsorption model that the potential in the adsorption plane changed with ionic strength with an opposite trend to the surface charge of these soils. The phosphate adsorption by these soils was related not only to the ionic strength but also to the types of electrolytes present. K+ induced a greater increase in phosphate adsorption than Na+ due to the greater affinity of the soils to K+ than Na+.

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Effect of Ionic Strength on Specific Adsorption of Ions by Variable Charge Soils: Experimental Testification on the Adsorption Model of Bowden et al.

Molecular Environmental Soil Science at the Interfaces in the Earth’s Critical Zone ◽

10.1007/978-3-642-05297-2_24 ◽

2010 ◽

pp. 78-80 ◽

Cited By ~ 2

Author(s):

Renkou Xu ◽

Jun Jiang ◽

Cheng Cheng

Keyword(s):

Ionic Strength ◽

Specific Adsorption ◽

Adsorption Model ◽

Variable Charge ◽

Specific Adsorption Of Ions ◽

Variable Charge Soils

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Microparticle Deposition on Human Serum Albumin Layers: Unraveling Anomalous Adsorption Mechanism

Colloids and Interfaces ◽

10.3390/colloids4040051 ◽

2020 ◽

Vol 4 (4) ◽

pp. 51

Author(s):

Małgorzata Nattich-Rak ◽

Maria Dąbkowska ◽

Zbigniew Adamczyk

Keyword(s):

Ionic Strength ◽

Human Serum Albumin ◽

Zeta Potential ◽

Serum Albumin ◽

Human Serum ◽

Electrostatic Interactions ◽

Surface Concentration ◽

Dlvo Theory ◽

Adsorption Model ◽

Negative Zeta Potential

Human serum albumin (HSA) layers are adsorbed on mica under controlled diffusion transport at pH 3.5 and various ionic strengths. The surface concentration of HSA is directly determined by AFM imaging of single molecules. It is shown that the adsorption kinetics derived in this way is quantitatively described using the random sequential (RSA) adsorption model. The electrokinetic characteristics of the HSA layers at various pHs comprising their zeta potential are acquired in situ while using the streaming potential method. It is shown that at pH 3.5 the zeta potential of mica becomes positive for HSA concentrations above 3000 μm−2. At larger pHs, HSA layers exhibit negative zeta potential for the entire range of coverage. Thorough characteristics of these monolayers at various pHs were performed applying the colloid deposition method involving negatively charged polystyrene microparticles. The kinetics of their deposition and their maximum coverage are determined as a function of the HSA layer surface concentration, pH, and ionic strength. An anomalous deposition of microparticles on substrates also exhibiting a negative zeta potential is observed, which contradicts the Derjaguin, Landau, Vervey, Overbeek (DLVO) theory. This effect is interpreted in terms of heterogeneous charge distribution that results from molecule concentration fluctuations. It is also shown that the maximum concentration of microparticles abruptly decreases with the electric double-layer thickness that is regulated by changing ionic strength, which indicates that their deposition is governed by electrostatic interactions. One can argue that the results obtained in this work can be exploited as useful reference data for the analysis of deposition phenomena of bioparticles on protein layers.

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Effect of pH, Ionic Strength and Heavy Metal Ions on p-Nitrophenol Adsorption by Variable Charge Soil of South China

Asian Journal of Chemistry ◽

10.14233/ajchem.2014.15788 ◽

2014 ◽

Vol 26 (9) ◽

pp. 2655-2660 ◽

Cited By ~ 2

Author(s):

J.Y. Zhang ◽

C.D. Wu ◽

Z.L. Zhang

Keyword(s):

Heavy Metal ◽

Ionic Strength ◽

Metal Ions ◽

South China ◽

Heavy Metal Ions ◽

Effect Of Ph ◽

Variable Charge ◽

Variable Charge Soil

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Effects of pH and Ionic Strength on Zinc Sorption by a Variable Charge Soil

Communications in Soil Science and Plant Analysis ◽

10.1081/lcss-200028914 ◽

2005 ◽

Vol 35 (15-16) ◽

pp. 2087-2095 ◽

Cited By ~ 7

Author(s):

José C. Casagrande ◽

Luís R. F. Alleoni ◽

Otávio A. de Camargo ◽

André D. Arnone

Keyword(s):

Ionic Strength ◽

Variable Charge ◽

Effects Of Ph ◽

Variable Charge Soil

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Phosphate Adsorption on γ-Alumina: A Surface Complex Model Based on Surface Characterization and Zeta Potential Measurements

The Journal of Physical Chemistry C ◽

10.1021/acs.jpcc.0c11553 ◽

2021 ◽

Author(s):

Teddy Roy ◽

Dorothea Wisser ◽

Mickaël Rivallan ◽

Manuel Corral Valero ◽

Thibaut Corre ◽

...

Keyword(s):

Zeta Potential ◽

Surface Characterization ◽

Complex Model ◽

Phosphate Adsorption ◽

Surface Complex ◽

Model Based

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Effects of pH and ionic strength on the cation exchange capacity of soils with variable charge

Soil Research ◽

10.1071/sr9810093 ◽

1981 ◽

Vol 19 (1) ◽

pp. 93 ◽

Cited By ~ 30

Author(s):

GP Gillman

Keyword(s):

Ionic Strength ◽

Cation Exchange ◽

Cation Exchange Capacity ◽

Exchange Capacity ◽

Surface Soils ◽

Ph Values ◽

Variable Charge ◽

Effects Of Ph ◽

Variable Charge Soils

The cation exchange capacity of six surface soils from north Queensland and Hawaii has been measured over a range of pH values (4-6) and ionic strength values (0.003-0.05). The results show that for variable charge soils, modest changes in electrolyte ionic strength are as important in their effect on caton exchange capacity as are changes in pH values.

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Effect of arsenate on adsorption of Zn(II) by three variable charge soils

Soil Research ◽

10.1071/sr06181 ◽

2007 ◽

Vol 45 (6) ◽

pp. 465 ◽

Cited By ~ 5

Author(s):

Jing Liang ◽

Ren-kou Xu ◽

Diwakar Tiwari ◽

An-zhen Zhao

Keyword(s):

Zeta Potential ◽

Surface Charge ◽

Iron Oxides ◽

Initial Concentration ◽

Variable Charge ◽

Study Results ◽

Negative Surface ◽

Negative Surface Charge ◽

Enhanced Adsorption ◽

Variable Charge Soils

The effect of arsenate on adsorption of Zn(II) in 3 variable charge soils (Hyper-Rhodic Ferralsol, Rhodic Ferralsol, and Haplic Acrisol) and the desorption of pre-adsorbed Zn(II) in the presence of arsenate were investigated in this study. Results showed that the presence of arsenate led to an increase in both the adsorption and desorption of Zn(II) in these variable charge soils. It was also suggested that the enhanced Zn(II) adsorption by arsenate was mainly due to the increase in negative surface charge of the soils induced by the specific adsorption of arsenate, and the increase in electrostatically adsorbed Zn(II) was responsible for the increase in the desorption of Zn(II). The effect of arsenate on Zn(II) adsorption primarily depends on the initial concentration of arsenate and Zn(II), the system pH, and the nature of soils. The enhanced adsorption of Zn(II) increased with the increase in the initial concentration of arsenate and the amount of arsenate adsorbed by the soils. The presence of arsenate decreased the zeta potential of soil suspensions and soil IEP and thus shifted the adsorption edge of Zn(II) to a lower pH region. The effect of arsenate on Zn(II) adsorption in these 3 soils followed the order Hyper-Rhodic Ferralsol > Rhodic Ferralsol > Haplic Acrisol, which was consistent to the contents of iron oxides in these soils and the amount of arsenate adsorbed by the soils.

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