Adsorption of heavy metal ions from aqueous solution by fly ash

The removal characteristics of lead and copper ions from aqueous solution by fly ash were investigated under various conditions of contact time, pH and temperature. The influence of pH of the metal ion solutions on the uptake levels of the metal ions by fly ash were carried out between pH 4 and 12. The level of uptake of Pb2+ and Cu2+ ions by the fly ash generally increased, but not in a progressive manner, at higher pH values. The effect of temperature on the uptake of Pb2+ and Cu2+ ions was investigated between 30 °C and 60 °C, the adsorption of being enhanced at the lowest temperature. Rate constants were evaluated in terms of a first-order kinetics. The rate constant, k for uptake of Pb2+ and Cu2+ ions were 1.77 × 10−2 s−1 and 2.11 × 10−2 s−1, respectively. The experimental results underline the potential of coal fly ash for the recovery of metal ions from waste water. The main mechanisms involved in the removal of heavy metal ions from solution were adsorption at the surface of the fly ash and precipitation.