surface charge

Soil language

surface charge It refers to the charge generated by isomorphic replacement or surface functional group ionization of soil minerals. According to the mechanism of charge generation, surface charge can be divided into permanent charge and variable charge. 2: Type 1 Clay mineral The surface is mainly permanent negative charge, but there is little permanent negative charge in 1:1 clay minerals. Hematite, goethite and Gibbsite Mainly variable charge, there is no permanent negative charge. Soil is a mixed system with permanent charge and variable charge. Clay minerals in cold temperate soil are mainly 2:1 type layered silicate, and the surface charge is mainly permanent negative charge. Tropical and subtropical soils are rich in kaolinite, iron and aluminum oxides, and the surface charge is mainly variable. The amount of surface charges of various soils varies greatly.^[1]

Chinese name: surface charge

English name: surface charge

definition: The net charge reflected on the surface of colloidal particles.

Applied discipline: Soil science (first level discipline), soil chemistry (second level discipline)

The above contents are provided by National Commission for the Examination and Approval of Scientific and Technological Terms Reviewed and published

Chinese name: surface charge
Foreign name: surface charge

definition: The net charge reflected on the surface of colloidal particles.
Applied discipline: Soil science (first level discipline), soil chemistry (second level discipline)

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three determination

definition

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surface charge That is Interface The charge present at. There are many processes that can make the surface Electrification , such as Ion adsorption 、 Protonation Or deprotonation, ionization of chemical groups on the surface, and external electric field. The surface charge will produce an electric field, which will make the particles repel or attract each other, which is the cause of many colloidal properties.

Object in fluid Generally, it will be charged. Almost all fluids will contain Ions , including positive ions（ cation ）And negative ions (anions), ions and surfaces will have Interaction , causing ions to be adsorbed on the object surface.

influence factor

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Soil colloid composition

Different soils contain different types of minerals Clay mineral The nature and quantity of electric charges vary greatly.

Particle size

Different particle sizes Soil particle Of negative charge The quantity depends on its mineral composition and humus Content, their impact on soil negative charge The contribution of Particle size Part of the content. In Chinese paddy soil Clay particle Some negative charges account for more than 80% of the total negative charges.

pH

Permanent charge is not affected pH But variable charge varies with pH. With the increase of pH, the variable negative charge increases and the variable positive charge decreases.

Nonadditivity of charge

Phosphate radical Isooxygenate in soil colloid The specific adsorption on the surface can increase the negative charge on the surface. The surface charge of soil is nonadditive. This is because the mineral and organic parts in the soil are not mechanically mixed, but Chemical bond Bonding Exists. Different kinds of mineral colloids or organic colloids are not mechanically mixed, but interlaced, intermingled, coated or combined. Therefore, the nonadditivity of surface charge is between the components of soil colloid Interaction Results.^[1]

determination

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The amount of surface charge of soil can be measured by ion adsorption method (Schofield method) or potential Titrimetry determination. Among them, ion adsorption is widely used, Potentiometric titration It is mostly used in variable charge system.

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