Removal of basic dyes from aqueous solutions by activated carbon prepared from Tamarindus indica fruit shells

Activated carbon prepared from Tamarindus Indica fruit shells has been used for the removal of two basic dyes, namely, rhodamine B and malachite green from aqueous solutions. Freundlich, Langmuir and Redlich-Peterson isotherm equations were used to fit the equilibrium adsorption data and the isotherm parameters were evaluated. The Langmuir monolayer adsorption capacity was found to be 3.1 mg/g for rhodamine B and 68.7 mg/g for malachite green at 30°C. The sorption processes were rapid and appear to follow pseudo-second order kinetics. Amounts of dyes adsorbed increased with increase in solution pH. Thermodynamic studies reveal that the sorption processes are endothermic and thermodynamic parameters like, ΔG, ΔH and ΔS were evaluated. Results of desorption studies point that the dyes are chemisorbed onto the surface of the carbon sorbent.