The synthesis of zeolites from fly ash and the properties of the zeolite products

Fly ash produced during the combustion of powdered coal could be converted up to 45% into zeolite. By varying the experimental conditions different types of zeolite were produced, e.g. zeolite Na-P1, zeolite K-G and zeolite ZK19. By this zeolitization process the cation exchange capacity (CEC) was raised from 0.02 to circa 2.4 meq/g. Anionic heavy metals were largely extracted by the process water. Sorption experiments indicated that the selectivity series for zeolite Na-P1 is Ba>Cu>Cd≈Zn>Co>Ni. Besides cation exchange reactions, precipitation of hydroxides also played a role in the immobilization of heavy metals in the column experiments carried out. Column leaching experiments showed that relative to the original fly ash, the zeolitized fly ash has a better environmental quality. The results of the sorption experiments suggest that the zeolite product can be applied in environmental technology as an immobilizer of pollutants.