Impact of Surface Functional Groups on The Adsorption of Aliphatic Organic Acids from Aqueous Solutions on Granular Activated Charcoal

Abstract

Adsorption of aliphatic organic acid, such ar Formic, Acetic, Propionic and n-Butyric acids fi om aqueous solutions on the surface of granular activated charcoal was studied as a function of stirring time, concentration of adsorbate and evacuation temperature (105 degree C, 300 degree C and 800 degree C). Adsorption equilibrium war found to be established within four hours time in all cares of aliphatic organic acids having concentrations i.e. 0.005M and 0.01 M at temperature of 25 degree C, which may be due to the uniform distribution of active sites on the surface of adsorbent. Evacuation temperatures (105 degree C, 300 degree C and 800 degree C) showed a considerable positive effect on the extent of adsorption and it war found that the higher adsorption of the organic acid on the sample evacuated at 800 degree C may be due to the decomposition of surface oxides and evolution of CO and CO2 at high evacuation temperature, which make the surface non-polar and thereby increased surface area which result in greater adsorption of non-polar or weakly polar organic acid, because of high affinity for organic compounds whereas carbon possess surface functional group having high affinity for water molecules, and thereby decreasing the effective diameter of the pore opening which result in lower adsorption of organic compounds at 105 degree C. The amount of adsorption of organic acids constantly increases as the homologous series is ascending Linear form of Freundlich's and Langmuir equations were applied to the adsorption isotherms data and it was found that both the equations obeyed them well.