Rapid degradation of bisphenol A using air as the oxidant catalyzed by polynuclear phthalocyanine complexes under visible light irradiation

The photocatalytic dechlorination and destruction of bisphenol A (BPA) using air as the oxidant catalyzed by polynuclear phthalocyanine complexes under visible light irradiation have been studied. Among the four complexes studied (FePPc, CuPPc, ZnPPc, AlPPc), ZnPPc and AlPPc show high catalytic activities. Under ambient conditions of temperature and pressure, an initial BPA concentration of 1 mM in water was completely converted to CO2 and carboxylic acid in 20 min with a catalyst/substrate molar ratio of 2:100 using a 100 W tungsten lamp as the light source. Six HPLC peaks indicating intermediate products appeared in chromatograms monitored at 254 nm. Oxalic acid and maleic acid were detected as their methyl esters in the resulting solution by GC-MS after treated with trimethylsulfonium hydroxide. TOC measurements indicated that 21.3% of the carbon was mineralized after an hour of reaction. When sunlight was used as the light source, BPA could also be degraded efficiently. Full conversion of BPA and its intermediate products were observed in 40 min without stirring and blowing air. The results of ESR measurements suggested that the reaction possibly proceeded via the pathway with singlet oxygen. A possible reaction sequence of the degradation of BPA was proposed. The influences of catalyst/substrate molar ratio, flow rate of the air, and pH were investigated.