Kinetic and Thermodynamic Studies of the Adsorption of Crystal Violet onto Used Black Tea Leaves

• Main Authors: Mohammad Abul Hossain, Md T. al-Hassan
• Format: Article
• Language: English
• Published: Universidade Federal de Mato Grosso do Sul 2013-11-01
• Series: Orbital: The Electronic Journal of Chemistry
• Subjects: adsorption kinetics; crystal violet; used black tea leaves; adsorption thermodynamics
• Online Access: http://orbital.ufms.br/index.php/Chemistry/article/view/460

<span style="font-family: Times New Roman; font-size: small;"> </span><p class="MsoNormal" style="margin: 0in 0in 0pt; text-align: justify; text-justify: inter-ideograph;"><em>This study presents the kinetic and thermodynamic investigation of the adsorption of crystal violet (CV) on used black tea leaves (UBTL) from aqueous solution to evaluate the feasibility of the process. The effects of concentration, solution pH and temperature on adsorption kinetics were carried out in batch process. Kinetic studies have shown that the adsorption data partially follow simple first order, second order and pseudo second order kinetic equations for different initial concentrations at pH 2.0. The equilibrium amount adsorbed, equilibrium concentration and rate constant were calculated from better fitted pseudo second order kinetic plots for different initial concentrations. The equilibrium amount adsorbed (200 mg/g at 30 ^oC) increased with the increase of temperature, indicated endothermic nature of the adsorption. The apparent activation energy of adsorption was determined from Arrhenius plot using pseudo second order rate constant and the value, Ea = 83.1 kJ/mol, revealed the process is chemisorption. Thermodynamic parameters: DHo, DGo and DSo, were determined from the equilibrium adsorption constant and the results obtained confirmed that the adsorption process was feasible, less spontaneous and endothermic. The equilibrium amount adsorbed was found to be increased with increase of solution pH from 2.0 to 6.0 indicating electrostatic interaction between cationic CV with anionic surface of UBTL dominated at higher pH due to the low zero point charge of pH of UBTL.</em></p><span style="font-family: Times New Roman; font-size: small;"> </span>