AS(V) REMOVAL FROM AQUEOUS-SOLUTIONS BY FLY-ASH

The present work examines the possible use of fly ash, a by-product of coal power stations, as a means of removing arsenic (V) from water, o r equivalently, of restricting its movement in the solid wastes or the soil. Kinetic and equilibrium experiments were performed in order to evaluate the removal efficiency of lignite-based fly ash. Both adsorpt ion and desorption experiments were done at three pH levels, namely 4, 7 and 10. The results indicated that arsenic can be removed from water by fly ash, yet the degree of removal depended markedly on the pH. Re moval at pH 4, as demonstrated by the adsorption isotherms, was signif icantly higher than that at the other two pH values. For 80% removal o f arsenic, the solid phase concentration at pH 4 was up to 4 times gre ater than that at the other two pH levels. During the desorption studi es only a small amount of the pre-adsorbed arsenic was released into t he water. This amount was practically independent of the initial fly a sh loading. This indicates that adsorption of arsenic on fly ash is al most irreversible and, therefore, there are good prospects for arsenic fixation on fly ash in practical applications.