Cation exchange properties of K and Ca type zeolites were investigated using Na type zeolite synthesized from coal fly ash under hydrothermal conditions. The caion exchange capacity (CEC) of the Na type zeolite was about 300 meq / 100 g. The cation exchange amount of Ca type zeolite substituted from Na type zeolite was measured for NH4+ and PO4 3- in order to evaluate the efficiency of zeolite as a water purification agent.Na type zeolite was exchanged with K+ and Ca2+ in the pH region of around 7. The exchanged amount of K+ did not depend on the kinds of anion in the aqueous solution, while the amount of exchanged Ca2+ depended on them. It was found that the substitution percentage from Na+ to Ca2+ reached to about 90 % of CEC, if the cation exchange operation was repeated.In the cation exchange reaction for NH4+, Na type zeolite exchanged much more NH4+ than Ca type zeolite. In the case of PO43-, Ca type zeolite removed PO43- from the aqueous solution by the precipitation reaction between Ca2+ released from the zeolite and PO43- in the solution. On the other hand, Na type zeolite could not remove PO4 3- from the aqueous solution. In the adsorption behaviors of NH4+ and PO43- from the mixed aqueous solution with Ca type zeolite, approximately 90 % and 46 % removal was accomplished for NH4+ and PO 43-, respectively. The ion of PO4 3- was precipitated quantitatively with Ca2+ released from Ca type zeolite in the solution.
展开▼
