Degradation of antipyrine by heat activated persulfate

Heat activated persulfate is an emerging water treatment technology utilizing highly active sulfate radicals (SO4 center dot-) as the principal oxidizing agent. The objective of this study was to evaluate the degradation of antipyrine, a representative pharmaceutically active compound, in a heat-activated persulfate system. Bench-scale kinetics tests were conducted to evaluate the impacts of key factors controlling the treatment performance, including pH, chloride, alkalinity, dissolved oxygen, dissolved organic matters, chemical addition mode, and water matrices. Under different experimental conditions, the antipyrine degradation exhibited a pseudo-first-order kinetics pattern (R-2 > 0.95). Solution pH influenced the treatment efficiency because the fractions of different oxidizing agents were pH-dependent. SO4 center dot- predominated under an acidic condition, while hydroxyl radicals (OH center dot) gradually prevailed at a basic condition. Chloride could enhance the degradation at an appropriate concentration ([Cl-1]:[persulfate] = 10:1 in this study achieved a 80% removal of antipyrine within 2 h), but inhibited the treatment at other levels. The alkalinity species apparently reduced the reaction rate (k(obs) decreased from 7.5 x 10(-3) s(-1) to 3.4 x 10(-3) s(-1) when [HCO3](0):[Persulfate](0) was increased from 0:1 to 200:1). Dissolved organic matter decreased the antipyrine degradation rate by 76% when initial DOC increased from 0 to 10 mg/L due to their competition for sulfate radicals. Anaerobic condition (dissolved oxygen = 0.01 mg/L) improved the k(obs) by 20% compared with an aerobic condition (dissolved oxygen = 8.20 mg/L). A single step of persulfate addition favored the antipyrine degradation rate. The findings demonstrate that the heat-activated persulfate oxidation is a promising technology for water pollution caused by emerging contaminants such as pharmaceuticals, and the treatment is optimized only after the impacts of water characteristics and operation methods are carefully considered. (C) 2013 Published by Elsevier B.V.