Kinetic and thermodynamic studies of chlorophenol adsorption Onto ricinus communis pericarp activated carbon in aqueous Solutions

Abstract

This study reports the adsorption of 2-chlorophenol from aqueous solution using activated carbon prepared from pericarp of Ricinus communis by H2SO4 activation. The pericarp of Ricinus communis was activated by treating with H2SO4 solution followed by heating in an oven at 105 oC for 12 hrs. Batch adsorption experiments were also carried out as a function of pH, contact time, initial concentration of the adsorbate, adsorbent dosage and temperature of the solution. Adsorption of 2-chlorophenol by pericarp of Ricinus communis was observed to sharply increase from pH 2 to 6 then decreased up to pH 12. The adsorption of 2-chlorophenol was observed to decrease with the initial concentration increase and the adsorption increase with the dose of adsorbent increase. The 2-chlorophenol adsorption process was better represented by the Freundlich isotherm model than Langmuir, with correlation coefficient (r2 ) of 0.996. The maximum adsorption efficiencies were obtained 99.87% at 60 minute, 98.75% at pH 6 and 99.25% at 30 oC. The Kinetic of 2-chlorophenol adsorption followed the pseudo-first-order kinetic model as determined by the correlation (r2 =1) and higher agreement between qe and qexp. Thermodynamic parameters, enthalpy changes (ΔH), entropy change (ΔS), and Gibbs free energy change (ΔG) were also calculated for the uptake of pericarp of Ricinus communis. These parameters showed that adsorption on the surface of Ricinus communis were feasible, spontaneous in nature, and exothermic between temperatures of 20 and 30 oC. IR spectrum for loaded and unloaded pericarp of Ricinus communis was characterized by using FT-IR spectrophotometer. The maximum adsorption capacity was obtained 24.9675 mg/g at 60 minute, 24.6875 mg/g at pH 6 and 24.8125 mg/g adsorption of 2-chlorophenol by pericarp of Ricinus communis AC adsorbent. It can be concluded that pericarp of Ricinus communis is a good and cheap adsorbent with high potential for the adsorption and recovery of 2-chlorophenol from contaminated water and could therefore serve as effective and efficient biomass for treating drinking waters in terms of high adsorption capacity