Dissolution characteristics of granulated coal ash in different saline water conditions

Abstract

Granulate coal ash (GCA) has been widely used for improving both sediment and water environments in littoral regions. Dissolved ions from GCA have been pointed out to play an important role in the improvements of sediment and water environments. As the dissolution characteristics of a material in solvent depend on the solvent characteristics, this study attempts to clarify the dissolution characteristics of GCA under different saline water conditions. This may provide useful information for practical uses of GCA in different water environments. The experimental results showed that GCA dissolved more with increasing salinity of solvent. This suggests that GCA is more active in saline water environment rather than freshwater environment. Interestingly, larger releases of calcium ions were confirmed when the solvent salinity was higher than 1000 mg/L. This was because the calcium ions of calcium silicate hydrate (C–S–H) present in GCA were replaced by the sodium ions present in solvent. The solubility of C–S–H present in GCA was low comparing with that of C–S–H gels. Only 40% of the total C–S–H were influenced by the high salinity concentration (higher than 1000 mg/L). Furthermore, a higher solubility of GCA was observed after combusting GCA. Our results suggest that GCA should be combusted at 200 °C prior to use for obtaining a higher performance in improving water and sediment environments.