Removal of Reactive Dye by Adsorption over Chemical Pretreatment Coal based Bottom Ash

Abstract

The coal based bottom ash from Thailand Power Plant has been used as the adsorbent for the removal of reactive dye in aqueous solution. The bottom ash was pretreated with 1N HCl, 1N HNO3, and 30% H2O2 before the adsorption tests. Adsorption of the pretreated bottom ash has been studied as a function of particle size, contact time, initial solution pH, and initial solution concentration. The ability to adsorb reactive dye (in terms of percentage dye removal) of these chemical treated bottom ashes are not significantly different. The adsorption reached an equilibrium state at about 15hours from the beginning of the experiments. The adsorption capacity at the equilibrium state increased as the size of the particles decreased. This was due to the increase in surface area of the adsorbents. The maximum adsorption occurred at the initial solution pH lower than 2 for all adsorbents with the highest percentage of dye removal and the highest amount dye adsorbed of 75.8 and 0.1mg/g adsorbents, respectively, for the H2O2 treated bottom ash. With varying the initial solution concentrations, the results showed that the adsorption capacity decreased as the initial solution concentration increased which was limited by the amount of the adsorbents in the system. Adsorption equilibrium data were fitted with both Langmuir and Freundlich adsorption isotherms with the correlation coefficient of 0.947 and 0.937, respectively.