Characterization of modified wheat straw, kinetic and equilibrium study about copper ion and methylene blue adsorption in batch mode

The citric acid modified wheat straw (MWS) was characterized and the adsorption properties of copper ion and methylene blue (MB) onto MWS were investigated in single adsorbate system by batch techniques. The mass loss during thermo-gravimetric analysis can be divided into steps related to moisture, cellulose and lignin. There were carbonyl group, hydroxyl group, etc. on surface of adsorbent from FTIR. Kinetic studies indicated that Cu2+ and MB adsorption followed the pseudo-second-order model. The adsorption may be controlled by external mass transfer followed by intra-particle diffusion mass transfer. The adsorption equilibrium data were fitted well by both the Freundlich and Langmuir models. The maximal equilibrium quantity of Cu2+ and MB from Langmuir model on MWS was 39.17 and 396.9 mg g−1 at 293 K, respectively. The thermodynamics parameters of adsorption systems indicated spontaneous and endothermic process.