Adsorption of 2,3-DCDD on FAU and EMT-type zeolites: Influence of the nature and the content of charge compensating cations

摘要

The nature and the content of exchangeable cations in FAU and EMT-type zeolites on the adsorption of dioxin are investigated. These zeolites are selected due to their pore openings, close to the diameter of the 2,3-dichlorodibenzo-p-dioxin (0.74 nm). In this study, the sodium cations, which balance the negative charge of the zeolitic framework, are replaced by other cationic species such as FT, Mg~(~(2+)), Li~+, Ca~(~(2+)), K~+ and Ag~+. The structural and textural analyses performed on the exchanged zeolites indicate that the exchange reaches 70-98% and the structure of zeolites is preserved during the exchange process. For both zeolite structure types, the dioxin adsorption rates are the highest for the sodium forms followed by the calcium forms. The following order is obtained: Na~+ >Ca~(2+) = Li~+ >Mg~(2+) = Ag~+ >K~+. It is also noticed that for a same type of zeolite (FAU), the adsorption rate is inversely proportional to the framework Si/Al molar ratio which is related to the content of sodium cations.