Effective adsorption of dyes on an activated carbon prepared from carboxymethyl cellulose: Experiments, characterization and advanced modelling

An activated carbon with a high surface area and outstanding adsorption properties was prepared for dye
removal from water. The new adsorbent was obtained from the chemical activation and pyrolysis of sodium
carboxymethyl cellulose (CMC). This activated carbon was employed to analyze and characterize the adsorption
mechanism of three dye molecules: methyl violet, allura red and congo red. Different characterization techniques
and experimental adsorption isotherms quantified at different temperatures (25–45 ◦C) were utilized to interpret
the dye adsorption mechanism. A double layer adsorption model was employed to estimate the steric and energetic
parameters associated with the adsorption of these dye molecules. The modelling results provided the
possible adsorption orientations of these dyes on adsorbent surfaces at different operating temperatures and the
number of bonded dye molecules per functional group of this adsorbent was also analyzed. Calculated adsorption
energies showed that both exothermic and endothermic processes were feasible for these dyes and physical forces
were involved in the adsorption mechanism. Overall, this new adsorbent showed a competitive performance for
dye removal in aqueous solution and can be a potential option for industrial applications.