Enhanced Microcystin Removal from Humic Acid-Rich Water: TiO2 Coated with MIL-101(Fe)

Microcystins are a group of potent hepatotoxins produced by cyanobacteria that can accumulate in water sources, posing a serious threat to human and animal health. The removal of microcystins from water is a challenging task, particularly in the presence of humic acids (HAs), which can interfere with the adsorption of microcystins onto sorbents. In this study, we propose a novel approach to mitigate the inhibitory effect of HAs on the adsorption of microcystins by coating TiO2 with MIL-101(Fe).

MIL-101(Fe) is a well-known metal-organic framework (MOF) that has high surface area and excellent adsorption properties. TiO2 is a widely used photocatalyst that can be easily coated onto various substrates. The combination of TiO2 and MIL-101(Fe) is expected to enhance the adsorption capacity of the sorbent and reduce the inhibitory effect of HAs.

To evaluate the effectiveness of the TiO2/MIL-101(Fe) sorbent, we tested its ability to remove two microcystin variants, D-Glu and D-MeAsp, from HA-rich water. The results showed that the TiO2/MIL-101(Fe) sorbent had a significantly higher adsorption capacity for both microcystin variants compared to TiO2 or MIL-101(Fe) alone. Moreover, the inhibitory effect of HAs on the adsorption of microcystins was greatly reduced by the TiO2/MIL-101(Fe) sorbent.

We also investigated the mechanism of microcystin adsorption onto the TiO2/MIL-101(Fe) sorbent using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results indicated that the adsorption of microcystins onto the sorbent was mainly driven by hydrogen bonding and electrostatic interactions.

In conclusion, our study demonstrates that coating TiO2 with MIL-101(Fe) can significantly enhance the adsorption capacity of the sorbent for microcystins, particularly in the presence of HAs. This approach has potential for the development of effective and efficient sorbents for the removal of microcystins from contaminated water sources.