Removal of bisphenols by slow sand filtration

A compensating effect in the reduction of bisphenols (BPs) has been shown using biodegradation in slow sand filtration and advanced photocatalysis. We tried to remove 8 kinds of BP by slow sand filtration. Removal rates of BPA, BPB, BPE, BPF, BPS, thiobisphenol (TBP), and dihydroxybenzophenone (DHB) indicated a high removal rate up to more than 90% at an initial concentration of 100 μg/L, whereas the removal rate of BPP was only 30%. We also examined removal of BPs by Pt-loaded porous photocatalyst under visible light irradiation. Removal rates of BPA, BPB, BPE, BPF, BPP, and TBP showed high removal rates up to more than 90% at an initial concentration of 10 mg/L. Removal of BPS and DHB was relatively low at 20% and 30%, respectively. Removal of BPP was low in slow sand filtration, but Pt-loaded photocatalyst removed BPP effectively. Removal of BPS was low with Pt-loaded photocatalyst, but slow sand filtration removed BPS effectively. The combination of a slow sand filter and Pt-loaded photocatalyst may be helpful to degrade BPs. The magnitude of decomposition of BPs by photocatalytic reaction may be related to electrophilic frontier density. But the degradability of BPs in slow sand filtration is not the same as that in photocatalytic reaction with Pt-loaded titanium dioxide. The biodegradability of BPs by slow sand filtration cannot be explained by molecular orbital calculation.