| This work has been finished on basis of the Wien effect measurements in dilute suspensions which was established recently. The principle and method of determining the distribution of conter-ions in double layers of soil colloidal particles by the Wien effect in suspensions were been described in the paper. The interactions of cations(Na+、K+、Ca2+Cd2+、Cu2+、Pb2+and La3+) and constant charge soil(yellow-brown soil and black soil), variable charge soil(red soil and latosol soil), the interactions of anions(F-、Cl-and N03-)and oxide(hematite and aluminium oxide)were investigated via Wien effect measurements in dilute suspensions; the distribution regularities of various ions in the double layers of colloidal particles were calculated as well. The major results of the work are summarized as follows:When the surface electrical conductivities of soil particles was larger than solution electrical conductivities under additional filed, the dipole moment was produced by ionic polarization as same as the direction of electric filed, the uplifted line was put up on the EC-E curve of ionic saturation then it shows positive Wien effect; Or the degressive line on the EC-E curve presents negative Wien effect. That was closely related to the combination and distribution of conter-ions in double layers of soil colloidal particles.Under the experimental conditions of the interaction between cation and constant charge soils, the surface electrical conductivities of colloidal particles of soils saturated with Na+are the largest, being0.494and0.617mS cm-1, respectively, for yellow-brown and black soils; whereas the cations which make the surface electrical conductivity the smallest are different, being Cu2+of0.0261mScm-1for yellow-brown soil, and Cd2+of0.0484mScm-1for black soil. The variation of surface electrical conductivity of colloidal particles of yellow-brown and black soils with cations is of the order Na+> K+> Cd2+Pb2+> Ca2+> La3+> Cu2+, and Na+> K+> Pb2+> La3+> Cu2+> Ca2+> Cd2+respectively. The ratios of almost all of cations besides Na+in the diffuse layer of colloidal particles, ECs/ECad, for yellow-brown soil are obviously less than those of black soil, in which Cd2+is only an addition, ECs/Ecad values of Cd2+in the diffuse layers of colloidal particles of yellow-brown and black soils are0.174, and0.0872, respectively. The variation of ζ potentials of colloidal particles of the two soils with cation valence, besides black soil saturated with Ca2+, possesses the same order as that of the surface electrical conductivities of soil particles.Under the tested pH values of the interaction between cation and variable charge soils, the surface electrical conductivities of colloidal particles of soils saturated with La3+are the largest; whereas the cations which make the surface electrical conductivity the smallest are different, being Cu2+of O.O121mmScm-1for red soil, and Pb2+of0.0174mScm-1for latosol. The variation of surface electrical conductivity of colloidal particles of red soil and latosol with cations is of the order La3+>Na+>K+>Ca2+>Pb2+>Cd2+>Cu2+, and La3+>Ca2+> Na+>K+>Cu2+>Cd2+>Pb2+respectively. They are follow the order trivalent ion> monovalent ion> divalent ion, besides latosol saturated with Ca2+. It was should be related to the properties of suspension for the abnormal ion. The ratios of cations in the diffuse layer of colloidal particles of red soil and latosol are Ca2+(0.104) and Cd2+(0.104) respectively. The ratios of almost all of cations besides Ca2+in the diffuse layer of colloidal particles, for red soil are less than those of latosol.The concave curve shows on EC-E curve of Wien effect in suspensions between anion and oxide is negative Wien effect. The onions which make the surface electrical conductivity the largest are NO3-and F" respectively. Whereas the surface electrical conductivities of oxides saturated with Cl-are the smallest. The variation of surface electrical conductivity of colloidal particles of oxides with onions are of the order NO3-> F-> Cl-and F-> NO3-> Cl-. The order is consistene well with the variation of ζ, potentials of colloidal particles of iron and aluminum oxide with onions. Effects of ionic strength on adsorption of phosphate and chromate in variable charge soils were investigated with batch method. The intersection of the pH scale on adsorption of oxyacid under different ionic strength was observed. The amount of phosphate and chromate adsorbed by variable charge soils increased with increasing ionic strength when pH was higher than the intersection, and when pH was lower a reverse trend was observed. The adsorptive mechanism was research by four-layer model, electrolyte affected the adsorption on the soils through its effect on electrostatic potential of the ionic specific adsorption plane, which existed between Stern layer and diffuse layer. It was proved by zeta potential of soil colloids varied with ionic strength. |
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