Abstract

Phosphate rock being locally abundant and cheap material in Jordan can be easily activated to become a promising adsorbent for phenol removal from aqueous solution. The phosphate rock before and after activation was characterized using XRD and IR techniques. The effects of various experimental parameters, such as initial phenol concentration, temperature, pH, contact time and adsorbent dose on the adsorption extent were investigated. Langmuir adsorption model was used for the mathematical description of the adsorption equilibrium and the equilibrium data fixed very well with this model. The activated phosphate rock had the monolayer adsorption capacity equal to 38.34 mg/g at pH value of 8.0 and 20°C, adsorption measurements show that the process is very fast and physical in nature. The extent of the phenol removal increased with decrease in the initial concentration of the phenol and temperature of solution. The results showed that as the amount of the adsorbent was increased, the % of phenol removal increased accordingly. Adsorption data were modeled using the pseudo-first and pseudo-second-order kinetic equations, Elovich and intra-particle diffusion models. It was seen that the pseudo- second-order kinetic equation could best describe the sorption kinetics. Thermodynamic parameters showed that the adsorption of phenol on activated phosphate rock was endothermic and spontaneous in nature.

Key words: Phenol, activated phosphate rock, adsorption isotherm, thermodynamic parameters, kinetics of adsorption, intra-particle diffusion, rate constant.