Typical Behavior Of Bisphenol A In Aqueous Environment Of Multi-media

It has been reported that BPA has estrogenic activity and acute toxicity toward aquatic organisms and human cultured cells (Nakagawa and Tayama, 2000). It has also been detected that the pollution of BPA can be created when using BPA to manufacture other compounds and products including releases from many current commodities. In this study,three typical behaviors of BPA in aqueous medium was investigated including adsorption behavior on sediments,biodegradation in aqueous medium and behavior in coagulation.The adsorption behavior of bisphenol A (BPA) on sediments was investigate through batch adsorption experiments. The sediment samples were collected from Xiangjiang River (Changsha, Central-south China). Data obtained from adsorption experiments show that the rapid adsorption plays the main role rather than slow adsorption in adsorption process of BPA on sediments. Freundlich model can describe the adsorption behavior of BPA on sediments very well. The calculated K_f (mg^1-n lⁿ g^-1 ) ranged from 0.0072 to 0.0178 (n ranged from 0.6944 to 0.8106). Through analyzing the data of adsorption experiments and properties of sediments, we consider that black carbon (e.g. soot- and charcoal-like material, collectively termed black carbon or BC) and hole-filling domain of the organic matters in sediment are responsible for the observed nonlinear adsorption and desorption hysteresis. The calculated hysteresis coefficient H ranged from 0.6718 to 1.0928. Negative and low molar formation enthalpy (â–³H⁰ = -5.735 kJ mol^-1) indicates that adsorption process of BPA on sediments is an exothermic reaction, attributed to the physical adsorption which is dominated by dispersive force and driven by enthalpy thoroughly. In this study, the amount of adsorbed BPA on sediment was found to decrease as sediment concentration increased, whereas it increased with an increase of ironic concentration. In acidic surroundings, the amount of adsorbed BPA on the sediment was found to decrease as pH value increased, whereas it varied indistinctively in alkaline surroundings.A novel bacterium designated strain B-16 was isolated from the compost leachate of the municipal solid waste (MSW) in a laboratory reactor. This strain was identified as a gram-negative bacterium, Achromobacter xylosoxidans that could grow on bisphenol A (BPA, a representative endocrine disruptor) as a sole carbon source under aerobic condition. BPA-degrading characteristics of strain B-16 were investigated in liquid cultures. The results show that BPA degradation was influenced by several factors (e.g. inoculum size, substrate concentration, temperature and pH, etc). The optimum temperature and pH were found to be 35℃and 7.0, respectively. BPA-degrading activity and cell growth were inhibited at high substrate concentration. Metabolic intermediates detected during the degradation process were identified as p-hydroxybenzaldehyde, p-hydroxybenzoic acid and p-hydroquinone, respectively. BPA was firstly metabolized to form three intermediates p-hydroxyacetophenone, p-hydroxybenzaldehyde and p-isopropenylphenol. Subsequently, there are three main pathways: Pathway (I), in which p-hydroxyacetophenone was oxidized to form p-hydroxybenzoic acid and that converted to carbon dioxide and biomass, Pathway (II), in which p-hydroxybenzaldehyde was converted to carbon dioxide and biomass directly, Pathway (III), in which p-isopropenylphenol was converted to p-hydroquinone by·OH radicals attack and mineralized later. The fact that p-hydroquinone accumulated during 4.5 d indicates that it was mineralized more slowly than other metabolites. Apparently, the relevant amounts or activities of the enzymes involved in the degradation pathway were significantly different.When the concentration of organic matter and turbidity was low in the solution, BPA was found to be removed by PAC coagulation to a certain extent at pH 5.0-6.0, attributed to the electronic counteract mechanism which is dominantwd by aluminous salts in the solution. The removal of BPA increased firstly as PAC dose increased, subsequently decreased. The optimal PAC dose was found at BPA/PAC=1:2(M/M). The humic matters and the turbidity matters in the solution has significant effect on BPA removal by PAC coagulation. The BPA removal will be weaken at high TOC and high turbidity.