Catalytic effects of activated-carbon particle size on the oxidative degradation mechanisms of a pharmaceutical

Abstract

The effects of the size of activated carbon (AC) on the catalytic degradation of organic micropollutants was investigated by the removal of a pharmaceutical (acetaminophen, ACT) using persulfate (PS). The removal of ACT, either by adsorption or oxidative degradation, and PS decomposition were enhanced by decreasing the size of the AC. The smallest AC particle (AC1) showed higher specific surface area, pore volume, macropores, and fractions of sp2-C and CO, but lower ID/IG, I2D/IG, and fractions of sp3-C and of O-CO, compared with the largest AC particle (AC6). Electron paramagnetic spectroscopy revealed a strong SO4•− signal for AC1, but the signal for AC6 appeared weaker after 30 min of reaction time. Decomposition of PS and peroxymonosulfate (PMS) was significantly enhanced by increasing the concentration of the electron donor (ACT) when AC1 was used, but it was not affected when AC6 was used. In addition, degradation of micropollutants and PS decomposition were seriously affected by their ionization potential when AC1 was used, and less affected when AC6 was used. These results suggest that the degradation of organic pollutants by AC1 + PS and AC6 + PS can be attributed primarily to the non-radical and radical pathways, respectively. Meanwhile, the catalytic activity was decreased as AC1 and AC6 were reused because of deactivation process. This indicates that the size of AC is a powerful determinant of the characteristics and can be optimized for the catalytic degradation of organic micropollutants.