REMOVAL OF PHENOLIC COMPOUNDS FROM AQUEOUS SOLUTIONS BY BIOSORPTION ONTO ACACIA LEUCOCEPHALA BARK POWDER: EQUILIBRIUM AND KINETIC STUDIES

Abstract

The aim of this work is to determine the potential application of Acacia leucocephala bark powder as a biosorbent for removing phenolic compounds from aqueous solutions.Experiments were carried out as function of initial pH (2-10), contact time, initial concentration of adsorbate (100-400 mg/L), and effect of adsorbent dosage.Adsorption of phenolic compounds (phenol, 2-chlorophenol (2-CPh) and 4-chlorophenol (4-CPh)) from aqueous solutions on bark powder was studied under batch equilibrium conditions.Maximum phenol removal was observed at pH 7.0.Increase in the pH to above neutrality resulted in the decrease in the phenolic compounds adsorption capacity.The adsorption process was fast, and it reached equilibrium in 4-h contact time.The kinetics study demonstrated that the adsorption process proceeded according to the pseudo-first-order kinetic model.Three isotherm models (Langmuir, Freundlich and Dubinin-Radushkevich) were employed in the analysis of the adsorption equilibrium data.The data fitted well with the Langmuir isotherm.The Langmuir model resulted in the best fit and the new adsorbent had maximum adsorption capacities for phenol, 2-CPh and 4-CPh of 94.33, 147.05 and 181.81 mg/g, respectively.The results indicated that the A. leucocephala bark powder could be an alternative for more costly adsorbents used for removal of phenolic compounds from aqueous media.