Adsorption of chlorophyll‐a from acetone solution on natural and activated bentonite

Abstract

Abstract The adsorption of chlorophyll‐a on bentonite desiccated at 110°C, untreated and acid‐treated with H 2 SO 4 solutions over a concentration range between 0·25 and 2·50 mol dm −3 , from acetone solution at 25°C has been studied. The adsorption isotherms may be classified as using Giles' classification, as type S (untreated sample and 0·25 mol dm −3 H 2 SO 4 ‐treated sample), type H (0·50 mol dm −3 H 2 SO 4 ‐treated sample) and type L (1·00 and 2·50 mol dm −3 H 2 SO 4 ‐treated samples). This fact suggests that the bentonite surfaces (low, high and medium affinity, respectively) behave in differently relation to the adsorption of the chlorophyll‐a molecules. The experimental data points have been fitted to the Freundlich equation in order to calculate the adsorption capacities ( K f ) of the samples; K f values range from 0·43 mg kg −1 for the untreated bentonite up to 108·89 mg kg −1 for the 0·50 M H 2 SO 4 ‐treated bentonite. The removal efficiencies ( R ) have also been calculated and range from 5·71% for the untreated bentonite up to 85·18% for the 0·50 M H 2 SO 4 ‐treated bentonite.