The character of dual site adsorbent on coal fly ash toward Pb (II) adsorption

Abstract

-Coal fly ash (CFA), generated during combustion of coal in the electricity production is recognized as an environmental pollutant. CFA is composed primarily of some oxides including SiO 2 , Al 2 O 3 having active site and unburned carbon that anables it to act as a dual site adsorbent. However, the existence of unburned carbon in coal fly ash can generate two possibilities. It can improve the adsorption capacity, or contradictionly hinder the adsorption.The aim of this paper is to study the contribution of unburned carbon on coal fly ash toward characters, adsorption capacity and adsorption mechanism. In this context, CFA with various unburned carbon content were employed as adsorbent of Pb(II) in aqueous solutions. The research shows that the existence of unburned carbon in CFA leads to the increase of specific surface area and pore size, but the adsorption capacity for Pb(II) decrease. Adsorption kinetics of Pb(II) onto CFA could be approximated with a pseudo second order kinetic model with the rate constant was 0.298 g.mg -1 .min -1 .