Study of natural adsorbent chitosan and derivatives for the removal of caffeine from water

The adsorption of caffeine was evaluated using natural adsorbent chitosan and three derivates of the material. Raw, H2O2 pre-treated, and a chemically altered chitosan were compared to activated carbon. Activated carbon was found to have a high affinity for caffeine (98% removal) while raw chitosan performed poorly with an average adsorption of 15.9%. Batch tests in acidic and basic conditions as well as increasing dosage did not have an effect on the performance. Chemical modifications to chitosan included calcinated mesoporous materials and non-calcinated materials, both of which increased chitosan adsorption of caffeine to 29 and 40%, respectively. Hydrogen peroxide pre-treated chitosan performed best of chitosan-based adsorbents, and reached a 46% removal of caffeine in batch adsorption tests. The majority of the adsorbents had low correlation to the Langmuir, Freundlich, and Redlich-Peterson isotherm models. However, data were sufficient to compare adsorption capacity for caffeine among activated carbon, chitosan, and chitosan derivatives.