Interfacial processes between zinc ions and different calcium soils (clayey soil, humate, bentonite, and sandy soil) were studied by a radioisotopic tracer method. Kinetic studies have shown that the process can be divided into two first-order steps, the activation energy of which is determined. The rate-determining step is diffusion. The sorptions of zinc ion on humate, clayey soil, and bentonite were found to be similar, but in the case of sandy soil, the process was slightly different. The process reaches an equilibrium state on each type of soil in 30-60 min. In equilibrium the amount sorbed is practically the same on humate, bentonite, and clayey soil, but significantly less on sandy soil. In the case of the interaction between calcium bentonite and zinc ions another interfacial process, which has to be taken into account in the evaluation of the resultant reaction, also takes place besides ion exchange.
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