Effect of superfine pulverization of powdered activated carbon on adsorption of carbamazepine in natural source waters

Abstract

The purpose of this study is to investigate adsorptive removal of carbamazepine from natural source waters by superfine pulverized powdered activated carbon. Superfine pulverization is becoming an increasingly attractive approach to decrease the diffusion path of a target adsorbate molecule and improve the overall the kinetics of activated carbon adsorption. Here we report the impact of pulverization on powdered activated carbon characteristics, and carbamazepine adsorption behavior in distilled and deionized water and natural organic matter solutions. The superfine pulverization decreased the particle size of activated carbon by 50 folds and the specific surface area by 24%. In addition, the micropore volume of the activated carbon decreased from 0.23 cm³/g to 0.14 cm³/g, while mesopore and macropore volumes increased from 0.15 cm³/g and 0.11 cm³/g to 0.18 cm³/g and 0.48 cm³/g, respectively. In terms of surface chemistry, the oxygen and iron contents of the activated carbon increased notably after pulverization. Despite the decrease in surface area and increase in surface polarity, the pulverization improved the adsorption kinetics especially for short contact times i.e., < 6-h. In general, the dissolved organic carbon concentration negatively influenced the kinetic advantage of superfine pulverized activated carbon. Isotherm results indicated that the parent adsorbent has a higher adsorption capacity than superfine activated carbon in distilled and deionized water and in natural waters. This was attributed to the losses in specific surface area and favorable sorption sites inside micropores. Our literature analysis indicated that unlike the small molecular weight hydrophilic organic compounds, the pseudo-equilibrium adsorption capacity could be increased or at least not deteriorated for hydrophobic molecules (K_ow > 3). Therefore, superfine pulverization of PAC can serve as a promising approach to remove micropollutants from natural source waters with a kinetic advantage.

Keywords: Adsorption kinetics; Pharmaceutical; Pulverization; Submicron carbon; Synthetic organic compounds.