Equilibrium, Thermodynamic and Kinetic Studies on Adsorption of a Basic Dye by Citrullus Lanatus Rind

An effective biosorbent was developed from Citrullus Lanatus Rind and its various biosorption characteristics were studied for removing a basic dye (Crystal Violet) from its aqueous solution. A series ofexperiments were conducted in a batch system to assess the effects of the system variables such as contacttime, biosorbent dosage, pH, initial dye concentration, temperature, particle size and agitation speed. The biosorbent studied exhibits high efficiency for crystal violet adsorption and the equilibrium states could be achieved in 180 min for the different initial concentrations. The equilibrium adsorption data were analyzed bythe Langmuir, Freundlich, Tempkin and Harkins-Jura isotherm models. The equilibrium data indicates thefollowing order to fit the isotherms: Freundlich > Tempkin > Harkins-Jura isotherm > Langmuir. The maximumdye adsorption capacity was found to be 11.99 mg/g at 50°C. The biosorption kinetics was found to followpseudo-second-order rate kinetic model, with good correlation (R = 0.99) and the intra particle 2 diffusion as oneof the rate determining steps. Different thermodynamic parameters, like Gibb’s free energy (ΔG), enthalpy (ΔH) andentropy (ΔS) of the adsorption process have also been evaluated. The thermodynamic parameters of crystal violetbiosorption indicated, the process was spontaneous and endothermic. The results indicated that the biosorbent studied was found to be a promising alternative for the adsorption of crystal violet from aqueous solution

Keywords:

Citrullus Lanatus Rind , Crystal Violet , Biosorption , Kinetics , Equilibrium , Thermodynamic