Kinetic and Equilibrium Studies of the Adsorption of Dichalcones on Activated Carbon

Abstract

This work is involved with the evaluation of the adsorption efficiency of an activated carbon prepared in our labs for the removal of two dichalcones namely; 2,6-Bis(4-Nitrobenzylidene) cyclohexanone and 2,6-Bis (4-Hydroxybenzylidene) cyclohexanone from their aqueous solutions. These chalcones were synthesized from the reaction of appropriate aldehydes (4- Nitro (or Hydroxy) benzaldehyde) and ketone (Cyclohexanone) and were employed as adsorbate for accomplishing this study. Optimization of the conditions of the systems considered were investigated concerning factors influencing adsorption efficiency such as adsorbent dose, time of contact, and chalcone initial concentration. Concentration of the adsorbed chalcones were determined spectrophotometrically. Calibration curve was constructed at the (λmax) of each chalcone. A batch method with single component systems were carried out for achieving the adsorption processes. The Freundlich and Langmuir adsorption isotherms were fitted to the practical data of adsorption at equilibrium within a concentration range (1*10^-4 – 9*10^-4M). The results showed a better fit of Freundlich isotherm to the experimental data of chalcone no.2, while, the Langmuir isotherm exhibited better fit to chalcone no.1. Kinetic study is performed by applying, pseudo first order and pseudo second order equations fitted to the practical data of the adsorption on activated carbon. The observed results indicated that the studied system are best followed the pseudo second order equation. This was determined by the values of R² close to unity (R² = 0.999 and 1.0) when compared with the first order (R² = 0.9169, 0.8829). In addition, the values of q_ex in the first order reaction are not consisted with the q_cal values.