Lime Potential

1997 ◽  
Author(s):  
J. H. Wang
Keyword(s):  
Calcium Ions ◽  
Chemical Potential ◽  
Earth Metal ◽  
Hydrogen Ions ◽  
Variable Charge ◽  
Aluminum Ions ◽  
Important Position ◽  
The 1960S ◽  
Ion Species ◽  
Variable Charge Soils

The properties of hydrogen and aluminum ions have been examined in Chapters 10 and 11. These two ion species are ions that directly induce the acid reaction in soils. In soils devoid of soluble salts, the content of cations is constant and the negative surface charges are saturated by, besides hydrogen and aluminum ions, alkali metal and alkaline earth metal ions. These ions are called base ions. The acidity of a soil is determined chiefly by the ratio of the quantity of hydrogen and aluminum ions to that of base ions. Among these base ions, calcium ions occupy the most important position, because they generally account for 65-80% of the total amount of base ions in variable charge soils. Therefore, calcium is an ion species closely related to the acidity of soils. In addition to the parameter pH that directly reflects the concentration of hydrogen ions, one other desirable way is to find a parameter that can reflect the ratio of the hydrogen ions to the calcium ions. This parameter is the lime potential. Since the introduction of the concept of lime potential 40 years ago, little practical application has been made in soil science, although some further theoretical considerations were advanced in the 1950s and the 1960s. Actually, as shall be seen in this chapter, for strongly acid soils, such as variable charge soils, because the quantity of hydrogen ions is too high and at the same time the quantity of calcium ions is too low, lime potential that can reflect the relative ratio of these two ion species is of significance not only in theory but also in practice. The mathematical expression of lime potential is pH-0.5pCa. Lime potential is a simple function of the chemical potential of calcium hydroxide, lime. Hence it may be called lime potential. The physical meaning of pH-0.5pCa can be derived as follows.

Acidity

1997 ◽  
Author(s):  
X. L. Kong ◽  
X. N. Zhang
Keyword(s):  
Surface Charge ◽  
Soil Acidity ◽  
Solid Phase ◽  
Hydrogen Ions ◽  
Variable Charge ◽  
Aluminum Ions ◽  
Acid Reaction ◽  
The Relationship ◽  
Constant Charge ◽  
Variable Charge Soils

For variable charge soils, acidity is a property that is of equal importance as the surface charge. These two properties may affect each other, with the effect of the former on the latter more remarkable than the reverse. In the previous chapters it was shown that pH affects many other properties of the soil by affecting the surface charge. Therefore, soil acidity is more significant than surface charge in some aspects. Owing to a similar reason, the importance of acidity for variable charge soils may exceed that for constant charge soils. Soil acidity generally manifests itself in the form of hydrogen ions. Actually, these hydrogen ions are chiefly the product of the hydrolysis of aluminum ions. Therefore, when examining soil acidity it is necessary to examine the properties of aluminum ions. In the previous chapter the transformation of hydrogen ions into aluminum ions has already been mentioned. In this chapter the relationship between aluminum ions and hydrogen ions will be discussed in greater detail. Another difference between variable charge soils and constant charge soils with respect to acidity is that, not only hydrogen ions, but also hydroxyl ions can participate in chemical reactions between the solid phase and the liquid phase. In constant charge soils the quantity of hydroxyl ions is an induced variable and is determined by the quantity of hydrogen ions in the solution and the ionic product of water. In variable charge soils, on the other hand, the quantity is also determined by the chemical equilibrium of that ion species itself at the solid-solution interface. Thus, hydroxyl ions can, in turn, affect the quantity of hydrogen ions in solution. In this chapter the nature of acidity of variable charge soils will be discussed mainly from these characteristics. In the field of soil chemistry, there has been an interesting history with regard to the nature of soil acidity. Soon after the recognition of the relationship between acid reaction and hydrogen ions in chemistry, this concept of the nature of acidity was introduced into soil science, and the significance of hydrogen ions was invariably associated with it whenever soil acidity was considered.

Reactions with Hydrogen Ions

1997 ◽  
Author(s):  
F. S. Zhang ◽  
T. R. Yu
Keyword(s):  
Ionization Energy ◽  
Alkali Metals ◽  
Chemical Properties ◽  
Hydrogen Ion ◽  
Hydrogen Ions ◽  
Soil Particles ◽  
Variable Charge ◽  
Hydrated Proton ◽  
Characteristic Features ◽  
Variable Charge Soils

Hydrogen ion is one kind of cation which possesses many properties common to all cations. Hydrogen ion also has its own characteristic features which are of particular significance for variable charge soils. The interactions between hydrogen ions and the surface of soil particles is the basic cause of the variability of both positive and negative surface charges of variable charge soils. The quantity of hydrogen ions in soils determines the acidity of the soil while the acidity of variable charge soils is among the strongest in all the soils. This strong acidity of variable charge soils affects many other chemical properties of the soil. In this chapter, the basic properties of hydrogen ions will be briefly discussed. Then, the products and the kinetics of the interaction between hydrogen ions and variable charge soils will be treated. The dissociation of hydrogen ions from the surface of soil particles has already been mentioned in Chapter 2. After the dissociation of an electron, a hydrogen atom becomes a proton (H+ ion). The ionization energy of hydrogen atoms is 1310 kj mol-1, whereas those of alkali metals, Li, Na, K, and Cs, are 519, 494, 419 and 377 kj mol-1, respectively. This difference in the ionization energy between hydrogen and alkali metals indicates that protons have a particularly strong affinity for electrons. Therefore, protons are apt to form a covalent bond with other atoms by sharing a pair of electrons, or to form a hydrogen bond. Because of the absence of an electronic shell, a proton has a diameter of the order of 10-13 cm, while other ions with electronic shells generally have a diameter of the order of 10-8 cm. Because a proton is so small, it is quite accessible to its neighboring ions and molecules. Therefore, there is very little steric hindrance when protons participate in chemical reactions. The above-mentioned features of proton are the basis for its particular properties. Free proton in solution is extremely unstable because it is very active. In an aqueous solution it will react with water molecules to form a hydrated proton, H3O+.

REACTIONS OF HYDROGEN IONS WITH VARIABLE CHARGE SOILS

Soil Science ◽  
1991 ◽  
Vol 151 (6) ◽  
pp. 436-443 ◽  
Author(s):  
F. S. ZHANG ◽  
X. N. ZHANG ◽  
T. R. YU
Keyword(s):  
Hydrogen Ions ◽  
Variable Charge ◽  
Variable Charge Soils

scholarly journals Influences of aluminum ions on the determination of zpc (zero point of charge) of variable charge soils

1989 ◽  
Vol 35 (4) ◽  
pp. 623-633 ◽  
Author(s):  
Katsutoshi Sakurai ◽  
Akinori Nakayama ◽  
Tsutomu Watanabe ◽  
Kazutake Kyuma
Keyword(s):  
Zero Point ◽  
Variable Charge ◽  
Zero Point Of Charge ◽  
Aluminum Ions ◽  
Variable Charge Soils

REACTIONS OF HYDROGEN IONS WITH VARIABLE CHARGE SOILS

Soil Science ◽  
1991 ◽  
Vol 152 (1) ◽  
pp. 25-32 ◽  
Author(s):  
F. S. ZHANG ◽  
G. L. LI ◽  
T. R. YU
Keyword(s):  
Hydrogen Ions ◽  
Variable Charge ◽  
Variable Charge Soils

Chemistry of Variable Charge Soils

1997 ◽  
Keyword(s):  
Soil Pollution ◽  
Management Practices ◽  
Chemical Properties ◽  
Soil Management ◽  
Soil Productivity ◽  
Basic Difference ◽  
The Past ◽  
Variable Charge ◽  
Constant Charge ◽  
Variable Charge Soils

This book, based on research carried out at the Academia Sinica over the past 30 years, explains the basic difference between the variable charge soils of tropical and subtropical regions, and the constant charge soils of temperate regions. It will focus on the chemical properties of the variable charge soils--properties which have important bearing on soil management practices, including maximizing soil productivity and combating soil pollution.

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

Soil Research ◽  
1981 ◽  
Vol 19 (1) ◽  
pp. 93 ◽  
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.

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

Soil Research ◽  
2007 ◽  
Vol 45 (6) ◽  
pp. 465 ◽  
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.

scholarly journals Modeling chemical reactions in porous media: a review

2021 ◽  
Vol 33 (6) ◽  
pp. 2279-2300
Author(s):  
Bettina Detmann
Keyword(s):  
Porous Media ◽  
Chemical Reactions ◽  
Chemical Potential ◽  
Mixture Theory ◽  
Reaction Diffusion ◽  
Second Law Of Thermodynamics ◽  
Reaction Diffusion Equations ◽  
Set Up ◽  
The 1960S ◽  
In The Beginning

AbstractFirst, different porous media theories are presented. Some approaches are based on the classical mixture theory for fluids introduced in the 1960s by Truesdell and Coworkers. One of the first researchers who extended the theory to porous media (thus mixtures containing at least one solid constituent) and also accounting for chemical reactions was Bowen. Another important branch of porous media theory goes back to Biot. In the beginning, he dealt with classical geotechnical problems and set up his model empirically. Mathematicians often use reaction–diffusion equations which are limited in comparison with continuum models by several restrictive assumptions and very often only applicable to special problems. In this paper, the focus lies on approaches based on the mixture theory which incorporate chemical reactions. Different strategies to describe the chemical potential for mixtures are presented, and different opinions about the exploitation of the second law of thermodynamics for mixtures are put forward. Finally, several works of different types including chemical reactions in porous media are summarized.

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