Carbon dioxide sorption isotherm and kinetics by alum sludge

Abstract

Carbon dioxide (CO2) can be considered as a hazardous gas due to its impacts to our environment and public health. Adsorption is an easy and simple technique to reduce CO2 level in the environment. Various waste materials have been applied as CO2 adsorbents, thus alum sludge which is a waste generated from a drinking water treatment plant was reused as CO2 sorbent in this study. The sorption kinetics, equilibrium, and thermodynamics of 1000 – 3000 mg/L of CO2were investigated using the sludge in a fixed bed column at 303 K. The results revealed that the maximum uptake of CO2 was 0.524 mmol.g-1 at 303 K. The isotherm of CO2 sorption was well-fitted with the Freundlich model due to closeness of the R2 to unity, whereas the sorption kinetics of CO2 on the sorbent was best described by pseudo-second-order kinetic model which is in good agreement with the experimental data. The sorption of CO2 using alum sludge is a spontaneous process as the value of Gibbs free energy change is negative. The results suggested that alum sludge could be a good candidate for CO2 sorption