Stability and chemical form of iodine sorbed on silver-exchanged zeolite X.

概要

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Neutron activation technique was used to measure the amounts of I, Ag and Na elements in zeolite samples. The samples were nonradioactive before the activation analysis ; this facilitated various operations to investigate the chemical form of the sorbed iodine. It was found that the Ag+ ions positioned in three types of sites react differently with iodine as follows : AgX•I2n, a physical adsorption product, released iodine immediately upon contact with water. (AgI)+ having a strong chemical bond did not release iodine either by heating or by submerging. (Ag …I)+ has a bond dissociation energy of several kcal•mol-1. When the sample was placed under water, part of the (Ag …I)+ ions released iodine very slowly and the remainder changed to thermally stable (AgI)+ ions. Ion-exchange reaction with aqueous sodium nitrate solution converted all of the (Ag …I)+ ions into stable AgI product. The Ag (3)+ ions reside in the inaccessible site for I atoms. The ratio of the populations was determined as :Ag(1)+ : Ag (2)+ : Ag (3)+= 0.33 : 0.51 : 0.16.
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