Activated carbon fiber for heterogeneous activation of persulfate: implication for the decolorization of azo dye.

Activated carbon fiber (ACF) was used as a green catalyst to activate persulfate (PS) for oxidative decolorization of azo dye. ACF demonstrated a higher activity than activated carbon (AC) to activate PS to decolorize Orange G (OG). The decolorization efficiency of OG increased as ACF loading, PS dosage, and temperature increased. OG decolorization followed a pseudo first-order kinetics, and the activation energy was 40.902 kJ/mol. pH had no apparent effect on OG decolorization. Radical quenching experiments with various radical scavengers (e.g., alcohols, phenol) showed that radical-induced decolorization of OG took place on the surface of ACF, and both SO and HO· were responsible for OG decolorization. The impact of inorganic salts was also evaluated because they are important compositions of dye wastewater. Cl and SO exhibited a promoting effect on OG decolorization, and the accelerating rate increased with elevating dosage of ions. Addition of Cl and SO could increase the adsorption of OG on ACF surface, thus favorable for OG decolorization caused by the surface-bound SO and HO·. Conversely, HCO and humic acid (HA) slightly inhibited OG decolorization. The azo band and naphthalene ring on OG were remarkably destructed to other intermediates and finally mineralized to CO and HO. [ABSTRACT FROM AUTHOR]