Adsorption of Crystal Violet on Used Black Tea Leaves from Acidic Solution: Equilibrium, Thermodynamic and Mechanism Studies

Mohammad Abul Hossain, Tanim-al- Hassan and Lokman Hossain

International Journal of Sciences, 2015, vol. 4, issue 10, 31-39

Abstract: The present study investigates the potential use of used black tea leaves (UBTL) for the removal of Crystal Violet (CV) from acidic solution in batch process. The influences of different adsorption parameters such as contact time, concentration, processing temperatures and ionic strength were investigated. UV-visible spectrophotometer was used to analysis CV at a specific pH (6.0) of solution. Several model isotherms were depicted at different processing temperatures using acidic solution of pH 2.0. Langmuir, Freundlich, Tempkin, Dubinin-Radushkevich (D-R) and Florry-Huggins model equation were subjected to analyze the equilibrium adsorption data. The experimental data reveals Langmuir and D-R models comparatively better fitted than Freundlich, Tempkin and Florry-Huggins models. The equilibrium adsorption capacity (qm) computed from Langmuir equation is 184.1 mg/g at 30oC which is increased with increase of processing temperature. The adsorption energy (E) calculated from D-R model indicates physical adsorption which plays cardinal role in this adsorption process. The value of separation factor informs that the adsorption process is favorable in nature. The effect of electrolytes (NaCl and NaNO3) suggests a possible adsorption mechanism of CV onto UBTL. The values of thermodynamic variables such as Gibbs free energy (∆Gads), enthalpy (∆Hads) and entropy (∆Sads) suggests the adsorption process is non-spontaneous, physisorption with negligible amount of fragmentation of dye molecules.

Keywords: Crystal Violet; used black tea leaves; adsorption isotherm models; thermodynamics (search for similar items in EconPapers)
Date: 2015
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DOI: 10.18483/ijSci.849

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