The use of fly ash to stabilise low concentrations of mercury in the environment.
University of Southampton, Engineering and the Environment,
The work investigates if fly ash from Ekibatuz Power Plant can stabilise low concentrations of mercury in the environment and prevent it from becoming soluble in water and in preventing it transforming into the methylated form. The work demonstrates that mercury bound to fly ash from the coal fired 4,000 Mwatt Ekibatuz Power Plant in Kazakhstan is fairly stable at pH levels that are found in most natural water bodies. The adsorption behavior followed the Freundlich adsorption model. The adsorption capacity of the fly ash for Hg (II) was found to be 3.0 mg.g-1 of dry ash, the adsorption equilibrium being reached after 96 hours. The adsorption kinetic and studied at pHs between 6 and 8. The study showed that between the pH range of 6.0 and 8.0 bound mercury on wet and air dried ash was fairly resistant to leaching with the maximum leaching being 0.292 mg.l-1 and 0.14 mg.l-1 for the wet and air dried fly ash, respectively, with leachate at pH 7.0. Laboratory studies of the stability of the adsorbed mercury on fly ash when mixed with organic rich sediments in an anaerobic environment at pH 7.0 showed that despite ideal conditions for methylation to take place after 8 weeks, the concentration in solution was less than 2 ?g.l-1. The studies showed that unburnt carbon contained in raw fly ash was the key factor for adsorption reaction. The results indicated that fly ash from the 4,000 Mwatt Ekibatuz Power Plant in Kazakhstan fired with high ash medium volatile coal can be used to stabilise low concentration of mercury in the natural aquatic environment
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