Comparative Study of Kinetics of Removal of Fuchsin Basic from Aqueous Solutions Using Biosorbents

Adsorption studies of Fuchsin Basic (FB) on six different agricultural wastes / natural materials were carried out by batch experiments. The parameters studied include initial dye concentration, adsorbent dose, pH, agitation time, agitation speed, particle size of adsorbent and temperature. The best fitting isotherm models were found to be Langmuir and Temkin. The monolayer (maximum) adsorption capacities (qm) were found between 166.667 to 250 mg/g for adsorbents under study. Among the kinetic models, Lagergen pseudo second order model best fits the kinetics of adsorption. Intra particle diffusion plot showed boundary layer effect and larger intercepts indicates greater contribution of surface sorption in rate determining step. Adsorption was found to increase on increasing pH, increasing temperature, increasing agitation speed and decreasing particle size. Thermodynamic analysis showed negative values of free energy change indicating adsorption was favourable and spontaneous, small positive values below 40 KJ/mole of enthalpy change indicating endothermic physical adsorption and positive values of entropy change indicating increased disorder and randomness at the solidsolution interface of FB with biosorbents. Adsorption capacity of pineapple peel powder towards FB was found to be more than other adsorbents under study.