Adsorption Behavior Of Bisphenol A On Different Iron Minerals

Bisphenol A（BPA） is a typical envrionmental endocrine disruptor widely used in the industrial and daily life. In recent years, it has been detected frequently in various types of environmental media. Because of its biological toxic effect, more and more people pay attention to it. In this study, we selected three kinds of typical iron minerals in the soil: ferrihydrite（include siliceous ferrihydrite）, geothite and siderite. The object of the subject was to investigate the adsorption behavior of Bisphenol A on different iron minerals. It was conducted by static adsorption bath experiments, supplemented by a variety of characterization techniques（XRD, Raman, SEM/TEM–EDX, BET-BJH, XPS, FTIR, TGA）. The results from our study indicated that:（1） The removal of BPA by ferrihydrite, geothite and siderite was 54%, 16% and 2%, respectively. As compared with goethite and siderite, ferrihydrite had a larger surface area, smaller particle size and pore size, which could provide more active adsorption sites. The dynamic processes between BPA and ferrihydrite, geothite, siderate were consistent with the pseudo second-order equation. The reaction equilibrium time was 12, 6, and 6h, respectively. The initial pH of solution d id not play an important role in the reaction system, and its effect was unobvious.（2） The results of the adsorption experiments between BPA and ferrihydrite, geothite, siderate could be described by the Freundlich model. But the results of the siderate system were more fitted by the Henry model, which indicated that its adsorption mechanism was simply physical distribution. However, the adsorption mechanism of BPA onto the ferrihydrite and geothite was phisical adsorption and surface chemical adsorption.（3） The presence of Fe（Ⅱ） had a little effect on ferrihydrite reaction system, but it had a significant promoting effect on the geothite and siderite system. Simultaneously, the presence of Fe（ Ⅲ） on ferrihydrite group was significantly inhibited, but it had little effect on goethite and siderite group（weak promotion）. This was possibly related to the status of iron ions.（4） The adsorption kinetics could be well described by the pseudo second-order equation for the reactions btween BPA and the different Si/（Si+Fe） molar ratios of siliceous ferrihydrites（5SiFh, 10 SiFh and 20SiFh）. The equilibrium time was 12, 6 and 6h, respectively. And the reactions were not only dependent on the spec ific area, particle size and other physical factors, but also affected by the chemica l composition of siliceous ferrihydrites. Besides, with the increasing of Si content, the adsorption capacity of BPA was decreased.（5） Since ferrihydrite had a good buffering capacity, the initial reaction pH value was not the main factor to affect the reaction of BPA with siliceous ferrihydrites. As the increase of the coexisting ions(Na⁺, Ca²⁺), they exhibited stronger inhibitant effect on the reaction. Meanwhile, the effect of Ca²⁺ was more obviously than Na⁺.