The effects of gas flow rate

temperature

pH value

initial mass concentration of 4-nitrophenol solution

and ultrasonic intensity on the decomposition efficiency of 4-nitrophenol by ultrasonic irradiation and ozone were studied. The results showed that the decomposition efficiency of 4-nitrophenol increased with the increase of gas flow rate

ultrasonic intensity and pH values (pH≤6)

and decreased with the increase of initial mass concentration of 4-nitrophenol solution

while both temperature and pH value (pH>6) were relatively not effective. The decomposition reactions of 4-nitrophenol by US/O3

US and O3 separately follow pseudo-first-order kinetics with rate constants 1.50×10-3 s-1，3.27×10-5 s-1 and 6.63×10-4 s-1 respectively

and the enhancement factor of 4-nitrophenol decomposition was around 216%. Ultrasound decomposed ozone

providing 8226;OH augmentation

which was the main cause of synergetic effect. The main intermediates during the decomposition included catechol

o-benzoquinone

hydroquinone

p-benzoquinone

phenol

fumaric acid

maleic acid

oxalic acid and formic acid as measured by high-performance liquid chromatograph (HPLC)

gas chromatograph coupled with mass spectrophotometer (GC-MS) and ion chromatograph (IC) techniques. The decomposition mechanism of 4-nitrophenol was also discussed.