Adsorptive Removal of p-Nitrophenol from Aqueous Solution by Bone Char: Equilibrium and Kinetic Studies

Para-nitrophenol adsorbed on bone char synthesized from cow bones has been studied. The Langmuir Freundlich and Sips models were applied to the equilibrium data to describe the adsorption process. The Langmuir model best described the adsorption process with R = 0.919; and maximum adsorption capacity, qmax of 365.76 mg/g. Batch kinetic studies conformed to pseudo-second-order indicating that several mechanisms may be involved in the process and gave a value of 2.5 × 10 g/mg/min for the rate constant for the sorption of p-nitrophenol on bone char. The values of thermodynamic parameters, free energy ≈ -22.0 kJ/mol, enthalpy -20.2 kJ/mol and entropy 5.34 J/K mol for the adsorption of p-nitrophenol on bone char showed that the adsorption was spontaneous and exothermic.