Adsorption behaviours of phenols onto high specific area activated carbon derived from Trapa bispinosa

Abstract

A low cost activated carbon derived from an aquatic plant Trapa bispinosa (TB) residue, has been characterized for the removal of phenol and its derivatives (p-chlorophenol and p-nitrophenol) from their aqueous solutions. The derived Trapa bispinosa husk (TBH) has micro porous and meso porous pore size distribution with high surface area (454 m² g^-1) and high carbon content (77%). The Langmuir, Freundlich, Redlich-Peterson and Temkin models have been applied to evaluate the adsorption parameters. The possible adsorption interactions have been discussed. The effects of pH, urea and ionic strength on the adsorption suggest that the adsorption of phenols is attributed to hydrogen bonding; however, hydrophobic interactions and charge transfer interactions are also believed to be responsible for the observed adsorption in the present case. The adsorption decreases in the order of p-chlorophenol > phenol > p-nitrophenol. Thermodynamic study demonstrates an endothermic nature of adsorption. Adsorption kinetics is examined using different kinetics model (Lagergren first order and pseudo second order). The best results have been achieved with the Langmuir isotherm equilibrium model and followed pseudo second order kinetics (R² = 0.99). The TBH is found to be very effective for removal of phenols from their aqueous solutions.