Mean Free Binding Energy And ITS Measurement Between Soil Clay And Ions

This work has been studied on basis of the Wien effect measurements in dilute suspensions which was established recently. The principles and methods of determining the mean free binding eneregy between cations with a variety of colloidal clays were investigated by the Wien effect method, ion activity method and DGT method (Diffusive Gradients in Thin-Films Technique). The interactions of cations (Na+, K+, Ca2+, Cu2+, Cd2+Pb2+and La3+) and two minerals (kaolinite and montmorillonite), four kinds of soil (black soil, yellow brown soil, red soil and latosol) and of anions (F-, Cl-and NO3-) and two kinds of oxides (hematite and y-aluminium oxide) were investigated. The major results were shown as follows:The mean free binding eneregy△Gbi between Na+and K+and soil particles via Wien effect and ion activity method were obtained. The results indicated that the mean free binding eneregy△Gbi via Wien effect method is of the order:yellow-brown soil> red soil> black soil> montmorillonite> kaolinite> latosol for Na+, and yellow-brown soil> black soil> red soil> montmorillonite> latosol> kaolinite for K+; via the ion activity method is of the order:red soil> black soil> yellow-brown soil> montmorillonite> kaolinite> latosol for Na+, and yellow-brown soil> black soil> latosol> red soil> montmorillonite> kaolinite for K+. The relative errors of the two methods are in the range of9.96%to810.33%. The△Gbi of Na+and K+on black soil and yellow-brown soil with the two different methods were quite similar, and on the red soil and montmorillonite were almost the same, but varied largely on the latosol soil and kaolinite.The mean free binding eneregy△Gbi between Ca2+, Cu2+, Cd2+and Pb2+and soil particles via Wien effect, ion activity and DGT methods were obtained. The results indicated that△Gbi via Wien effect is of the order:black soil> yellow-brown soil> red soil> montmorillonite> kaolinite> latosol for Ca2+. montmorillonite> black soil> yellow-brown soil> red soil> kaolinite> latosol for Cu2+, montmorillonite> red soil> black soil> yellow-brown soil> kaolinite> latosol for Cd2+, montmorillonite> black soil> red soil> yellow-brown soil> kaolinite> latosol for Pb2+; For the ion activity is of the order:black soil> yellow-brown soil> red soil> montmorillonite> kaolinite> latosol for Ca2+, montmorillonite> red soil> kaolinite> yellow-brown soil> black soil> latosol for Cu2+, montmorillonite> red soil>yellow-brown soil> black soil> latosol> kaolinite for Cd2+, black soil> montmorillonite> yellow-brown soil> red soil> latosol> kaolinite for Pb2+; For the DGT method is of the order:red soil> yellow-brown soil> black soil> latosol for Ca2+, black soil> yellow-brown soil> red soil> latosol for Cu2+, latosol> red soil> black soil> yellow-brown soil for Cd2+, black soil> latosol> red soil> yellow-brown soil for Pb2+. The three different methods to measure the△Gbi showed that ion activity method had a larger velue, while Wien effect method was lower, and DGT method in the middle. It may be ascribed that ECo is high and ion activity ai is low. There are some differences of the△Gbi by three methods.The mean free binding eneregy△Gbi between La3+and soil particles via Wien effect and ion activity method was obtained. The results indicated that the mean free binding eneregy△Gbi via Wien effect is of the order:montmorillonite> black soil> yellow-brown soil> red soil> kaolinite> latosol; For the ion activity is of the order:montmorillonite> yellow-brown soil> kaolinite> black soil> red soil> latosol. The relative errors of two methods varied from10.37%to1086%.The△Gbi for the latosol and kaolinite appeared negative, that may be latosol with the variable-charge soils, positive in charge, or the pH is not suitable for the measurement; For the kaolinite, that may be due to incomplete elution of the colloidal.The mean free binding eneregy△Gbi between F-, Cl-and NO3-and soil particles via Wien effect and ion activity method was obtained. The results indicated that the△Gbi via the two different methods are of the same order:γ-aluminium oxide> hematite. The relative errors of two methods were in the range of3.27%to41.2%.