Photodegradation pathways of cypermethrin as affected by copper

The influence of copper ion (Cu²⁺) on the photodegradation of cypermethrin (CPM) in aqueous solution was studied under a xenon lamp irradiation. The results showed that the lower concentration of Cu²⁺ (⩽10 mg/L) significantly promoted the photodegradation of CPM, which might be related to the reducing action of Cu²⁺, but the higher concentration of Cu²⁺ (100 mg/L) restrict the degradation efficiency, presumably due to the intensification of light filtering effect by the high concentration of Cu²⁺ which reduces the amount of light available for catalyst activation. The photodegradation kinetics of CPM followed the first-order reaction kinetics. The photodegradation products of CPM were analyzed by gas chromatography-mass spectrometry (GC-MS) and the possible photodegradation pathways were also proposed.