KINETIC AND EQUILIBRIUM STUDIES OF METHYLENE BLUE BIOSORPTION BY VINEYARD PRUNING WASTE

Abstract

Adsorption studies were conducted to measure the removal of methylene blue (MB) from aqueous solution on vineyard pruning waste (VPW) under varying experimental conditions, such as different pH values, initial concentrations, adsorbent dosages, ionic strength and temperatures. The adsorption amount increased with increasing pH from 3.0 to 11.0, and it was seen that the increase in ionic strength resulted in a decrease of adsorption amount. VPW exhibited the highest MB uptake capacity of 46.082 mg g(-1) at 298 K and natural pH. Kinetic studies were fitted to the pseudo-second-order kinetic model (R(2): 0.999). But, the first order kinetic model (R(2)< 0.960) and intra-particle model (R(2)< 0.973) did not adequately fit to experimental values. The diffusion coefficient values calculated for MB were in the range of 3.48x10(-9) to 38.10x10(-9) cm(2)s(-1). The equilibrium adsorption data were interpreted using Langmuir and Freundlich models, and the adsorption of MB on VPW was better represented by the Langmuir (R(2)> 0.990) than Freundlich (R(2)< 0.844) equation. Thermodynamic parameters; standard enthalpy (Delta H degrees), standard entropy (Delta S degrees) and standard free energy (Delta G degrees) were found to be -7,638 kJmol(-1) and -280.83 jmol(-1)K(-1), and 78.86 kJmol(-1), respectively. VPW was characterized by FTIR and scanning electron microscopy (SEM).