Phenol Adsorption onto Fly Ash from Aqueous Solution-Kinetic, Equilibrium and Thermodynamic Studies

摘要

Phenol and Phenolic compounds are water soluble and highly mobile and hence are likely to reach drinking water sources downstream from the discharges. Phenol is toxic to animals and humans and is known to be carcinogenic. Present study reports a systematic evaluation of fly ash for removal of phenol from aqueous solutions. Fly ash is a solid waste obtained from thermal power plant. Studies were carried out to investigate the effect of pH, initial phenol concentration, and adsorbent dosage level and equilibrium contact time for the adsorption process. The optimum pH was found to be 6.5. The equilibrium was achieved within 5 hr. of contact time. Maximum adsorption was achieved at an adsorbent dosage of 20 g/L. Kinetics data were best described by pseudo-second order model. The equilibrium adsorption data were better fitted to Longmuir isotherm model. The maximum adsorption capacity (qmax) of fly ash in terms of monolayer adsorption was 3.40 mg/g. The negative value of change in Gibbs free energy (Go) indicates the spontaneity of the adsorption process. The change in heat of adsorption (Ho) indicates that the adsorption of phenol by fly ash was exothermic in nature.