This study reports on the adsorption of 2-chlorophenol from an aqueous solution using activated carbon prepared by H 2 SO 4 activation of the pericarp of Ricinus communis (RCAC). The pericarp was carbonized and activated by treating with H 2 SO 4 solution followed by heating in an oven at 105°C for 12 hrs. Batch adsorption experiments were carried out as a function of pH, contact time, initial concentration of the adsorbate, adsorbent dosage and temperature of the solution. Kinetic data were best fit to a pseudo-first-order rate equation for the adsorption of 2-chlorophenol on RCAC. Thermodynamic parameters ΔH o , ΔS o and ΔG o for the adsorption were also determined which shows that adsorption on the surface of RCAC was spontaneous in nature, and exothermic between temperatures of 20°C and 80°C. The equilibrium data better fit the Langmuir isotherm model for 2-chlorophenol adsorption on RCAC. IR spectrum for loaded and unloaded RCAC was obtained and found to be in good agreement. ARTICLE HISTORY

Polyaniline (PANI) in its emeraldine salt form was synthesized by chemical method from aniline monomer in the presence of HCl mixed with LiCl and ammonium persulfate as oxidant. Then, a portion of sample was dedoped with NH 3 solution and another equal portion was separately postdoped with secondary dopants, such as H 2 SO 4 and HClO 4 , respectively. Finally, the dried samples of PANI prepared in all its three different forms (emeraldine salt form, undoped emeraldine base, and the two secondary doped forms of PANI) were characterized by UV-visible spectroscopy, cyclic voltammetry (CV) techniques, Fourier transform infrared (FT-IR) spectroscopy, and electrical conductivity measurement. The cyclic voltammograms of PANI in its emeraldine base (PANI-EB) determined the electrochemical behavior and the growth mechanisms of the polymer. The FT-IR and UVvis spectra confirmed the expected structural modification up on doping, undoping, and postdoping processes of the polymer. Their measured electrical conductivities were from 0.02 for undoped, 156 for primary doped form, and increasing from 158 to 257 S/cm for those secondary doped PANI. The influence of secondary doping on the electrical conductivity was also investigated from their spectroscopic data which shows dramatic rise in conductivity. The result also shows that secondary doping increased the π conjugation.

Charge transfer complex formation between 8-hydroxyquinoline as the electron donor and citric acid as the electron acceptor has been studied spectrophotometrically in ethanol and methanol solvents at room temperature. Absorption band due to charge transfer complex formation was observed near 320 and 325 nm in ethanol and methanol, respectively. The stoichiometric ratio of the complex has been found 3 : 1 by using Job’s and conductometric titration methods. Benesi-Hildebrand equation has been applied to estimate the formation constant and molecular extinction coefficient. It was found that the value of formation constant was larger in ethanol than in methanol. The physical parameters, ionization potential, and standard free energy change of the formed complex were determined and evaluated in the ethanol and methanol solvents.