Removal and recycling of aqueous selenite anions using cobalt-based metal–organic-framework coated on multi-walled carbon nanotubes composite membrane

Abstract

The utilization of selenium as a novel functional material is rapidly expanding, and the retrieval of selenium from waste containing selenium is gaining recognition in the industry. This study prepared a novel composite membrane coated with the cobalt-based metal–organic framework coated on multi-walled carbon nanotubes (Co-MOF@MWCNTs). The MWCNTs served as the skeleton to support the active components of Co-MOF, which enabled efficient removal and resource utilization of liquid selenite (SeO32−). The morphology, structure, and composition of the prepared membrane were characterized using field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), etc.. Applying a permeate flux of 67.08 L m−2 h−1, the SeO32− removal efficiency of the composite membrane reached up to 92.2%. The composite membrane containing CoSeO4 can be used as an electrocatalytic oxygen evolution catalyst. Density functional theory calculations and electrochemical analysis showed that the conversion from O* to OOH* was a rate-determining step. Under 1.0 M KOH conditions, the lowest overpotential for Co-MOF@MWCNTs-40 at 10 mA cm−2 was 360 mV. In this study, the process of selenium resource utilization and the mechanism of SeO32− removal by Co-MOF@MWCNTs are revealed. It demonstrates that membrane-based sequestration of SeO32− can provide a viable approach for SeO32− removal and utilization in wastewater.