阳离子对斜发沸石物理化学性能的影响

利用离子交换方法可以制备出K-型、Na-型和Ca-型斜发沸石。斜发沸石所含的阳离子类型不同,其物理化学性能有明显的差异。本文就不同类型的阳离子对斜发沸石的某些物理化学性能的影响进行了研究。

INFLUENCES OF CATIONS ON PHYSICAL AND CHEMICAL PROPERTIES OF CLINOPTILOLITE

Natural clinoptilolite can be transformed into K- Na- and Ca- form of clinoptilolite by cation exchange, but it can not be transformed into heulandite by means of general ion-exchange.Zeolitic water content of clinoptilolite is a function of the cation types. The water content of zeolite is reduced in order of Ca- form > Na- form > natural sample > K- form, in brief it is decreased with the increase of ion radius of the exchangeable cations.The difference in the exchangeable degrees of cations clearly appears after the clinoptilolite of various cation forms has been heated. During heating treatment influence of temperature on K-form and Na- form of clinoptilolite can be neglected, but it is significant on Ca-form of clinoptilolite. This difference may be attributed to those cations which occupy different cation localities in the crystal structure of clinoptilolite, and to the changes of structure of zeolite being occurred after its heating treatment.During heating treatment, the crystal structure of K- form of clinoptilolite is stable up to 750℃, and begins to destroy at 800℃; it is stabilized up to 700℃, and begins to destroy at 750℃ for Na- form; for Ca- form it begins to destroy at 400℃. Natural clinoptilolite can be considered as a kind of mixed clinoptilolite, the temperature for its initial destruction is at about 600-650℃, intermediate between Na- form and Ca- form. The thermostable sequence of various cation forms of clinoptilolite is:K- form > Na- form > natural sample > Ca- formThe cation type in the zeolites plays an important role, though Si/Al ratio is a dominating factor on the thermostability of clinoptilolite.