可变电荷土壤中特殊化学现象及其微观机制的研究进展

综述了近年来可变电荷土壤化学研究的进展,着重总结了可变电荷土壤中的盐吸附、铁铝氧化物对土壤自然酸化的抑制作用和离子强度对离子专性吸附的影响等特殊化学现象及其微观机制的研究进展。用颗粒表面扩散层重叠导致有效电荷数量减小的原理解释了盐吸附现象和铁铝氧化物对土壤自然酸化的抑制作用。阐明了可变电荷土壤和矿物中介质离子强度影响离子专性吸附的机制,用四层吸附模型解释了离子专性吸附随离子强度增大而增加的现象,并根据胶体zeta电位随离子强度改变而变化的趋势进一步证明了离子强度增大使胶体专性吸附面上静电电位的绝对值减小,是离子专性吸附随离子强度增大而增加的主要原因。带电颗粒表面双电层结构和双电层相互作用的深入研究,有助于阐明可变电荷土壤中一些特殊化学现象的微观机理,从而进一步完善土壤化学理论。

Progresses in research on special chemical phenomena and their mechanisms in variable charge soils

In this paper, the authors summarized progresses in the study on variable charge soil chemistry in recent years with emphasis on special chemical phenomena, such as salt adsorption, the effect of Fe/Al oxides inhibiting natural acidification of the soil and the effect of ionic strength affecting specific adsorption of ions and their microscopic mechanisms in the soil. The phenomena of salt adsorption and iron and aluminum oxides inhibiting natural acidification of the soil can be explained with the principle of overlapping of diffuse layers on the surfaces of oppositely charged particles which led to decrease in effective surface charge in the soils. The authors also elucidated the mechanism of ionic strength affecting specific adsorption of anions and heavy metal cations by variable charge soils and explained the effect with a four-layer adsorption model, and further verified on the basis of the variation of zeta potential of the colloids with ionic strength that electrostatic potential in specific adsorption planes of colloids decreases in absolute value with rising ionic strength, which is the main cause for the increase in specific adsorption of anions and heavy metals by the soils and Fe/Al oxides. The extensive investigation of the interactions between the electric double layers on oppositely charged particles and the structure of electric double layer not only helps elucidation of some of the special chemical phenomena in variable charge soils, but also enriches theories of variable charge soil chemistry.