Studies In Ion-exchange Of Zeolites And Application For Absorbents And Antibacterial Agents

A large body of pertinent literature on solid-state ion exchange in zeolites exists, but its mechanism is yet not clear, and still the degree of exchange in many reactions cannot meet the practical needs. Therefore, the solid-state ion exchange reactions of NaA zeolite are studied in this paper. And a novel method for the preparation of metal containing small pore zeolites is described. Studies in zeolites such prepared as absorbents and antibacterial agents are given.First, solid-state ion exchange reactions between LiCl, Li2CO3,KCl, Zn(NO3)2, ZnCl2, CuCl2, AgNO3 and NaA zeolite are firstlystudied, which are investigated by ICP, XRD, FT-IR and 23NaMNR. It is shown that the defusing is the major controlling procedure in the solid-state ion exchange process of NaA zeolite, and the temperature and the ratio of Men+/Al affect the rate and degree of exchange of reaction; In addition, the reaction between zeolite and compounds is reversible, so it is necessary to severely control the temperature and the concentration of reactants, which supplements the early investigated results: the time is negligible in solid-state ion exchange of zeolites. The presence of strongly bound Na+ ions in cationic positions prevents the stabilization of polyvalent metal cations. Thus, the HT or NH4+ forms of zeolites are the preferred starting materials. On the contrary, the presence of small amount of water may facilitate the solid-state ion exchange, though it is not a prerequisite for the solid-state introduction of metal ions into zeolites. The comparative study is carried out between the two ways of "the two step way" and "the solid-state ion exchange". It can be concluded that the degree of exchange may be higher by "the two-step way" in many cases except for the insoluble compounds such as Li2CO3.Second, the absorption properties of NaA exchanged by LiCl are described in this paper.Finally, the investigations on the antibacterial properties and the method of stabilizing the color of antibacterial zeolites are carried out, in which the NaA zeolite is the matrix, and Ag+ ion is the antibacterial component. The results show that the antibacterial properties of such prepared zeolites are very excellent, and the antibacterial rate can reach 100%. It is also found that the inorganic ZnO film cause little discoloration, however, other methods such as using organic films are not preferred and it needs further studies.