Kinetic and equilibrium study of adsorption of Di-Azo dyes on commercial activated carbon

This research work is concerned with studying the adsorption of a number of di-azo dyes on commercial activated carbon (cac). the synthesized dyes vary in their structures by the central parts,which are either ortho,meta or para phenylene diamine. this variation affects the linearity of molecules,their spatial arrangement and electron movement throughout the molecule by resonance. factors affecting adsorption process,such as the effect of contact time,initial concentration,ph of the adsorption medium,adsorbent dose,effect of solvent and temperature were studied. the results indicated that,the adsorption process is fast in the first 10 min,then gradually decreased with time and approaches maximum within 70-80 min for all the studied dyes. the increase of initial concentration and temperature decreased the adsorption efficiency. the results also shows that,the adsorption is found to be more efficient at low ph value. the increase of the adsorbent dose increases the adsorption efficiency and decreases its capacity. the variation of solvent (ethanol-water ratio) indicates that the decrease of dielectric constant lowers the adsorption efficiency. the study included application of three adsorption isotherms; freundlich,langmuir and tempkin on the experimental data of the studied systems. the results indicated that,freundlich isotherm fits better the adsorption data. kinetic analysis of the adsorption data was also conducted by employing 4 kinetic models; pseudo first order and pseudo second order,elovich and intra particle diffusion equations. the results obtained conclude that,the studied systems follow the pseudo second order model.