Physicochemical characterization of Spanish fly ashes

This article summarizes the results obtained from the physical, chemical, a nd mineralogical characterization of 14 fly ash samples. Major features tha t influence the utilization of each fly ash for zeolite synthesis are evide nced and several fly ash types were selected as potential high-quality star ting material for zeolite synthesis and ceramic applications. The main para meters influencing this selection were relatively small grain size; high Al and St contents; high glass content; low CaO, S, and Fe contents; and rela tively low heavy metal concentration. The Compostilla and Dou He fly ashes have high potential applications because of the low content of major impuri ties (such as Ca, Fe, and S) and the low content of soluble hazardous eleme nts. The Espiel, Escucha, Los Barrios, As Pontes, Sore de Ribera, Meirama, Narcea, and Teruel fly ashes have important application potential, but this potential is slightly limited by the intermediate content of nonreactive i mpurities, such as Fe and Ca. The La Robla fly ash is of moderate interest, since the relatively high Ca and Fe oxide contents may reduce its potentia l applications. Finally, the Puertollano fly ash also has limited applicati on because of the very high concentration of some heavy metals such as As, Cd, Ge, Hg, Pb, and Zn. From a mineralogical point of view, the Compostilla , Espiel, and Sore de Ribera fly ashes show the highest aluminum-silicate g lass content and consequently, the highest industrial application potential .