Sandwiched fluorinated nanofiltration membrane for enhanced removal of micromolecular organic chemicals in petrochemical wastewater

Abstract

The petrochemical industry discharges large amounts of wastewater containing various micromolecular organics, but existing technologies are difficult to remove them, which poses serious challenges to ecosystems and human health. Herein, a novel nanofiltration membrane with alternating hydrophilic–hydrophobic functional layers was developed. The enhanced removal and mechanism of typical micromolecular organics, including N,N-dimethylformamide (DMF), aromatic compounds and long-chain hydrocarbons in petrochemical wastewater were investigated. The modified membrane was assembled alternately with polytetrafluoroethylene (PTFE) and polyvinyl alcohol − maleic acid − sodium styrene sulfonate (PMS). The introduction of hydrophilic PMS underlayer reduced the aggregation of hydrophobic PTFE, leading to the formation of uniform and smaller membrane pores (i.e., from 0.45 nm to 0.22 nm). The alternating hydrophilic–hydrophobic layers overcome the limitations of the single hydrophilic interaction and can efficiently remove broad-spectrum micromolecular pollutants (e.g., the DMF removal efficiency is increased by 64.7 %) and decrease membrane fouling by 88.5 %, which compensates for the performance defects of conventional nanofiltration membranes. Moreover, the novel membrane was proven to be effective in treating petrochemical wastewater, meeting discharge standards and maintaining excellent performance stability after six cycles. This study proposed an attractive approach for the construction of high-efficiency nanofiltration membranes for the deep purification of industrial wastewater containing micromolecular pollutants.