Fast removal of cyanobacterial toxin microcystin-LR by a low-cytotoxic microgel-Fe(Ⅲ) complex

Eutrophication has become a serious environmental threat throughout the world. In particular, the presence of cyanobacteria toxins, especially microcystins (MCs), has become a severe problem. Inhibition of Microcystis growth in water resources is the most effective way to reduce MCs, but it is a long-term investment. In the present study, a microgel-Fe(Ⅲ) complex was developed for the fast removal of MC-LR. The microgel-Fe(Ⅲ) characteristics and the MC-LR removal dynamics in Milli-Q water and natural water were evaluated. The removal efficiency negatively correlated to the initial MC-LR concentration and pH value (2.0–11.5), but the kinetics was not significantly influenced. The presence of natural organic matter (NOM) in water slightly reduced MC-LR removal using microgel-Fe(Ⅲ). In addition, microgel-Fe(Ⅲ) removed 98.99% of MC-LR in 12 min, while for activated carbon, it took 15–24 h to reach equilibrium. Furthermore, methanol was found to regenerate the microgel-Fe(Ⅲ) after MC-LR removal for at least five regeneration cycles. Finally, the microgel-Fe(Ⅲ) material was made into a membrane so that MCs could be removed by filtration. Therefore, microgel-Fe(Ⅲ) is an effective technology and has a great potential in removing MC-LR from drinking water resources.

► A microgel-Fe3+ complex was developed to fast removal of microcystins.
► Removal efficiency negatively correlated to the initial MC-LR concentration and pH.
► Up to 98% of MC-LR was removed in 12 min with low effect to natural organic matter.
► The microgel-Fe3+ complex can bind with filter for further application.