Fixation by adsorption from aqueous solution of the methylene blue on the Powder graphite

The powder graphite (PG) was used as a support adsorbent for the removal of the cationic dye, methylene blue (MB), from aqueous solution. The effects of major variables governing the efficiency of the process such as, temperature, initial dye concentration, mass of the adsorbent, the contact time and solution pH were investigated. The equilibrium time was found to be 10 min for 10 mg/L dye concentrations of 25mL of volume. The point of zero charge value pH(Zero) determined by titration method and the effect of pH study, explain that the electrostatic attractive interactions pH > pH(Zero), promote the fixing of dye on the PG with increasing pH. Two simplified kinetic models including pseudo-first-order and pseudo-second-order equation were selected to follow the adsorption processes. The kinetics studies indicated that the pseudo-second-order model yielded the best fit for the kinetic data. The equilibrium data were best represented by the Dubinin isotherm model, by which we determined the adsorption energy. The thermodynamic study, says that the adsorption reaction is endothermic, spontaneous and more favorable at high temperatures and the adsorption of chemical type. This study is also used for measuring specific surface areas S-sp = 31.79m(2) / g of the powder graphite.