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 thar the selectivity series for zeolite Na-PI is Ba > Cu > Cd approximate to 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. (C) 1998 Elsevier Science B.V. All rights reserved.