Removal of Ammonium from Aqueous Solution by Granulated Coal Ash.

Granulated coal ash is made by granulating fly ash from coal-fired power plants with a small amount of cement and water as binders, which is recommended as an absorbent for hydrogen sulfide and nutrient salts adsorptions. Therefore, granulated coal ash is widely used for improving sediment and water quality in littoral regions. Specifically, a scattered layer of granulated coal ash on the seabed can reduce the diffusion of nutrient salts from sediments to bottom waters. It is believed that a granulated coal ash layer on the seafloor adsorbs nutrient salts, and releases ions, which can form insoluble complexes with ammonium ions. However, the processes by which granulated coal ash affects removal of ammonium ions are still unclear. This study describes the results of laboratory experiments performed to examine the processes related to the suppression of ammonium ions diffused from sediments. In particular, the removal of ammonium ions from aqueous solution (ammonium chloride solution) due to the released ions from granulated coal ash and hydrates present in granulated coal ash is examined. The achievements from this study may provide useful information for expanding the practical uses of granulated coal ash, and for developing a new improved granulated coal ash-derived absorbent. The experimental results showed that the released ions from granulated coal ash have no ability, on their own, to remove ammonium ions from the ammonium chloride solution despite the presence of a small amount of dissolved phosphate derived from granulated coal ash. It was determined that the removal of ammonium ions performed by hydrates present in granulated coal ash. 700°C-heated granulated coal ash (hydrate-removed granulated coal ash) was unable to remove ammonium ions from the ammonium chloride solution. This also ensured that ammonium molecules were unable to adsorb onto granulated coal ash surface. [ABSTRACT FROM AUTHOR]