Kinetic and Equilibrium Studies of Coomassie Blue G-250 Adsorption on Apricot Stone Activated Carbon

Abstract

The preparation of Activated Carbon from Apricot Stone (ASAC) with H3PO4 and its ability to remove the Coomassie Blue (CB) used in textile industry from aqueous solutions are reported in this study. The FTIR spectroscopy is used to get information on interactions between the adsorbent and CB. A series of contact time experiments were undertaken in stirred batch adsorber to assess the effect of the system variables. The results were discussed and showed that ASAC can be used in the wastewater treatment. A comparison of two models on the overall adsorption rate showed that the kinetic of adsorption was better described by the pseudo-second order model. The adsorption isotherms of CB onto ASAC are determined and correlated with common isotherms equations. The smaller RMSE values obtained for the Freundlich model indicate the better curve fitting; the monolayer adsorption capacity of CB is found to be 10.09 mg/g at temperature 22.5 °C and 98.022 mg/g at temperature 50 °C and pH ~ 2. The thermodynamic parameters indicate the spontaneous and exothermic nature of the adsorption process. The positive value of the entropy (ΔS) clearly that the randomness in decreased at the solid-solution interface during the CB adsorption onto ASAC, indicating that some structural exchange may occur among the active sites of the adsorbent and the ions. The activation energy (66.161 kJ/ mol) indicates that the chemical adsorption was predominant.