Removal of methylene blue, a basic dye from aqueous solutions by adsorption using teak tree ( Tectona grandis) bark powder
Systematic batch mode studies of adsorption of methylene blue (MB) on teak tree bark powder (TTBP) were carried out as a function of process of parameters includes initial MB concentration, dose of adsorbent, pH, agitation time, agitation speed, temperature and particle size. TTBP was found to have excellent adsorption capacity. Freundlich, Langmuir and Temkin isotherm models were used to test the equilibrium data. The best fitting isotherm models was found to be Langmuir and Freundlich. The linear regression coefficient R2 was used to elucidate the best fitting isotherm model (R2 ≈ 0.99). The monolayer (maximum) adsorption capacity (qm) was found to be 333.333 mg g-l for TTBP. The dimensionless separation factor (RL) values lie between 0.015 to 0.3289 indicated favourable adsorption. Lagergen pseudo -first order, Lagergen pseudo -second order, Natrajan and Khalaffrrst order, Bhattacharya Venkobachar first order and Elovich kinetic models were tested for the kinetic study. Lagergen pseudo -second order model best fits the kinetics of adsorption (R2 = 1, qe(the) ≈ qe(exp)). Intra particle diffusion model showed boundary layer effect and larger intercepts indicates contribution of surface adsorption was high in rate controlling step. Adsorption was found to increase on increasing pH, increasing temperature and decreasing particle size. Thermodynamic analysis showed negative values of i1G indicating adsorption was favourable and spontaneous, positive values of L1H indicating endothermic physical adsorption and positive values of i1S indicating increased disorder and randomness at the solid-solution interface of MB with the adsorbent TTBP.