Abstract

ADSORPTION KINETICS FOR THE REMOVAL OF METHYLENE BLUE FROM AQUEOUS SOLUTIONS ON JACKFRUIT (ARTOCARPUS HETEROPHYLLUS) PLANT LEAF POWDER

*Satish Patil, Sameer Renukdas and Naseema Patel

Abstract

Adsorption of methylene blue (MB) on jackfruit plant leaf powder (JPLP) was studied by batch experiments. The parameter studied includes initial MB concentration, dose of adsorbent, pH, agitation time, agitation speed, temperature and particle size. JPLP was found to have excellent adsorption capacity. Freundlich, Langmuir and Temkin isotherm models were used to test the equilibrium data. The best fitting isotherm model was found to be Langmuir with linear regression coefficient (R2 ≈ 0.99).The monolayer adsorption capacity (qm) were found to be 333.333 mg g-1 of JPLP. A dimensionless separation factor (RL) value lies between 0 to 1. Lagergen pseudo -second order model (R2 = 1) and Bhattacharya and Venkobachar first order model (R2 > 0.99) best fits the kinetics of adsorption. The overall rate constant, Kad obtained from Natarajan and Khalaf for adsorption of MB decreases with increase in concentration and the forward rate constant was much higher than the reverse rate constant suggesting that the rate of adsorption was dominant. 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 and decreasing particle size. Thermodynamic analysis showed negative values of ΔG indicating adsorption was favourable and spontaneous, positive values of ΔH indicating endothermic physisorption and positive values of ΔS indicating increased disorder and randomness at the solid- solution interface of MB with JPLP.

Keywords: Adsorption isotherm, methylene blue, Jackfruit plant leaf powder.