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

Abstract

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  determined by titration method and the effect of pH study, explain that the electrostatic attractive interactions, 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  of the powder graphite.