Potential environmental applications of pure zeolitic material synthesizedfrom fly ash

A pure 4A/X (60/40) zeolite product was synthesized from silica extracts of the Meirama fly ash in northwestern Spain. A high cation-exchange capacity (4.7 meq/g) was obtained for the zeolitic material. The potential applicat ion of this coal fly ash conversion product for decontamination of high hea vy metal waters was evaluated using three high heavy metal waters from acid mine drainage around the pyrite Huelva belt. The results were compared wit h those obtained with an equivalent pure commercial synthetic zeolite. A co nsiderable reduction in the heavy metal content was attained (Zn from 174 t o <0.1 mg/L, Cu from 36 to 0.1 mg/L, Fe from 444 to 0.8 mg/L, Mn from 74 to <0.1 mg/L, Pb from 1.5 to <0.1 mg/L, and Cd from 0.4 to <0.1 mg/L), even i n high Ca and Fe waters using zeolite doses from 5 to 30 mg/L. Both precipi tation and cation-exchange processes accounted for the reduction in the pol lutant concentration in the treated waters. Leachable hazardous elements fr om coal fly ash, such as Mo, B, As, V, and Cr, were not fixed in the synthe sis of pure zeolites from the silica extracts. Consequently, they did not r estrict the potential applications of this material as an ion exchanger, un like the zeolitic material obtained from fly ash by direct alkaline convers ion.