Initial Bisphenol A Concentration Research Articles

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 CO 2 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.

Photooxidation of bisphenol A (BPA) in water in the presence of ferric and carboxylate salts

In this work, the photooxidation of bisphenol A (BPA), a suspected endocrine disruptor (ED), in water in the presence of ferric and oxalate ions was investigated in a concentric reactor under a 125 W high-pressure mercury lamp (lambda> or = 365 nm). The photooxidation efficiencies were dependent on the pH values and ferric/oxalate concentration ratios (Fe(III)/Ox) in the water, with higher efficiency at pH 3.50+/-0.05 and Fe(III)/Ox 10.0/120.0 micromol l(-1). The initial rate of photooxidation increases with increasing the initial concentration of BPA from 2.0 to 5.0 mg l(-1) while do not change at 5.0 and 10.0 mg l(-1). However, higher removal efficiency of BPA is archived at lower BPA initial concentration over range of 2.0 to 10.0 mg l(-1). For 2.0 mg l(-1) BPA, the initial rate of photooxidation is 0.06 mg l(-1)min(-1). By using UV-Vis spectrum and LC-MS techniques, the predominant photooxidation product BPA-o-catechol was identified and the mechanisms for the oxidative degradation were proposed. When BPA reacted with OH radicals, C atoms in 3-position were added with OH radicals followed by O2 peroxidation and HO2 radical escape. Then catechol derivatives were produced. After that, the two H atoms on the hydroxy group were extracted in two individual steps to form intermediates semiquinone radical and o-quinone. The intermediates underwent further oxidation, benzene ring cleavage and decarboxylation, up to mineralization ultimately.

Degradation of bisphenol A in water by the photo-Fenton reaction

The photodegradation of bisphenol A (BPA), a representative endocrine disrupting chemical, was carried out in the presence of the Fenton reagent. The degradation rate was strongly influenced by the pH, and initial concentrations of H 2O 2 and Fe(II). An initial BPA concentration of 10 mg l −1 was completely degraded after 9 min under the optimum conditions. This reaction was found to follow the first order kinetics law. The formation of CO 2 as a result of mineralization of BPA was observed during the photo-Fenton process. The degree of BPA conversion to CO 2 was more than 90% under UV irradiation for 36 h. The decomposition of BPA during the photo-Fenton treatment gave six kinds of intermediate products, such as phenol, p-hydroquinone, etc. The degradation mechanism of BPA was proposed on the base of the evidence of the identified intermediates. Based on these results, the photo-Fenton reaction could be useful technology for the treatment of wastewater containing BPA.

Degradation of bisphenol A in water by TiO2 photocatalyst.

The photocatalytic degradation of bisphenol A (BPA), a representative endocrine disruptor, was carried out in TiO2 aqueous suspension. The main purposes were to confirm the total mineralization of BPA and to evaluate the estrogenic activity in the treated water during the photocatalytic reaction. An initial BPA concentration of 175 microM in water was totally degraded to carbon dioxide by TiO2-photocatalyzed reactions under UV irradiation of 10 mW cm-2 for 20 h. Four HPLC peaks indicating intermediate products appeared in chromatograms monitored at 275 nm, but the heights relative to that of the initial BPA were very low, at most 0.04 in the time period 5-10 h after the start of UV irradiation. All of the peaks finally disappeared after 20 h. For the treated water, the transcriptional estrogenic activity in response to human estrogen receptor in a yeast hybrid assay decreased drastically to less than 1% of the initial BPA's activity within 4 h. On the basis of these results, we conclude that TiO2 photocatalysis could be a useful technology for the purification of water containing BPA without generating any serious secondary pollution.