What is the Phanerozoic Eon?

Cation substitution ^[1] refers to the exchange of cations adsorbed on soil colloids and cations in soil solution. Soil colloids are mostly anions, and the outer layer is adsorbed with cations, some of which can be exchanged with cations in the soil solution.

Cation substitution refers to the exchange of cations adsorbed on soil colloids and cations in soil solution. Soil colloids are mostly anions, and the outer layer is adsorbed with cations, some of which can be exchanged with cations in the soil solution. Through exchange, most cations can be absorbed and utilized by plants. The order of the various cation substitution forces is consistent with their coagulation force on the sol.

Ion exchange membrane is a kind of polymer electrolyte material. The active group on the membrane structure has dissociable ions, so it has the unique characteristics of load current and ion selective permeability. Cation exchange membranes have cation exchange groups, such as those with strong acidic cation exchange membranes with sulfonic acid groups, and those with carboxylic acid, phosphorous (phosphonic) acid and other groups are weakly acidic cation exchange membranes. Cation exchange membranes have the characteristic of selective transmission of cations in solution, and are mainly used in membrane separation technologies such as electrodialysis, reverse osmosis, water treatment, separation and purification, and electrolysis technology. ^[2]

Two methods are generally used for the preparation of cation exchange membranes. The first is the modification of the membrane body, which is mainly to adjust a process parameter (especially the degree of cross-linking) to produce a suitable unipolar membrane, which is mixed with an acid and a metal divalent salt solution. When in contact, the flux of protons is higher than the flux of metal ions; the second is the surface treatment of the membrane, which includes increasing the density of the membrane surface and depositing a thin anion exchange layer on the surface of the cation membrane, which generates a positive charge, thus generating a The electric repulsive barrier limits the relative penetration of other valence cations. If the crosslinking agent is slightly increased, the selectivity of divalent ions relative to monovalent ions decreases.

Most of the soil colloids are negatively charged, and the cations in the diffusion layer exchange with the cations in the soil solution. The cation substitution is carried out in an equivalent relationship, which is a reversible reaction, which can quickly reach equilibrium, and the speed of the process is not affected by temperature and soil reaction. The order of the various cation substitution forces is consistent with their coagulation force on the sol, and is governed by the law of mass action, that is, the greater the ion concentration, the stronger the substitution ability. The total amount of all substitutional cations per 100 grams of dry soil is called "basic substitution amount", or "total substitution cations", which can also be referred to as "substitution amount" for "mg equivalent / 100 "Kertu". The top soils with high replacement volume are generally fertile soils ^[3] .