✍ Scribed by Natàlia Moreno; Xavier Querol; Felicià Plana; José Manuel Andres; Maria Janssen; Heng Nugteren
No coin nor oath required. For personal study only.
Pure zeolites can be synthesised from silica extracted from fly ash by alkaline leaching. If the process is optimised the solid residue arising from this extraction may also contain a relatively high content of zeolitic material mixed with residual fly ash components. Both the pure and the impure zeolitic material have a high potential for application in waste‐water and flue gas‐cleaning technologies. The silica extraction potential of 23 European coal fly ashes covering most of the possible fly ash types is investigated in this study. Optimisation of leaching processes, by varying temperature, time and alkali/fly ash rates, permitted extraction yields up to 140 g of SiO~2~ per kg using a single step process, but the extraction yields may reach up to 210 g kg^−1^ by applying thermal pre‐treatments prior to the extraction. The solid residue arising from the silica extraction experiments shows a high NaP1 zeolite content. A high Si/Al ratio of the glass matrix, the occurrence of easily soluble silica phases in the original fly ash and a high reactive surface area were found to be the major parameters influencing silica extraction. High purity 4A and X zeolitic material was obtained by combining the silica extracts from the Meirama fly ash and a waste solution from the Al‐anodising industry. The results allowed conversion of the silica extraction yields to an equivalent 630 g of pure 4A–X zeolite per kg of fly ash with a cation exchange capacity of 4.7 meq g^−1^.
© 2002 Society of Chemical Industry
📜 SIMILAR VOLUMES
## Abstract Zeolitic material is obtained from fly ash both by direct conversion of the ash or from SiO~2~ extracts obtained from fly ash. This study focuses on determining the suitability of a fly ash for SiO~2~ extraction and for zeolite synthesis by direct conversion. The SiO~2~ extraction exper
## Abstract Fly ash samples from the Bayswater and Eraring power plants, located in New South Wales, Australia, were used in a preliminary study on zeolite synthesis by hydrothermal treatment with sodium hydroxide under various conditions. The treated fly ash was tested for the ability to remove le
## Abstract The main objective of this study was to investigate the reaction mechanism of zeolitization from coal fly ash by alkali hydrothermal treatment. The hydrothermal synthesis of zeolites was carried out using various alkali sources. The changes in the various properties, such as crystal str