Robust superhydrophilic and underwater superoleophobic membrane based on copper-organic framework modified carbon nanotube for oil-water and dye separation

Abstract

With the rapid development of industry, the discharge of wastewater containing emulsified oils and water-soluble dyes has been increasing, posing a serious threat to the environment and human health. Therefore, the development of an easy-to-manufacture, energy-efficient and highly effective separating material has become a top priority. In this study, copper-based metal-organic frameworks (Cu-MOFs) were combined with carbon nanotubes (CNTs) by hydrothermal synthesis as well as superhydrophilic mixed matrix membranes (MMMs) were constructed using ultrasonication and vacuum-assisted self-assembly techniques. As a result, the prepared Cu-MOF@CNT membranes exhibited excellent separation efficiency (flux of 5376 L m⁻² h⁻¹, and separation efficiency of 97.7 %) in treating hexane emulsion, which was attributed to their excellent water permeability and oil rejection. In addition, due to the porous and negatively charged surface of the Cu-MOF@CNT membranes, their removal of cationic dyes (gentian violet (GV) and methylene blue (MB)) were efficient, which was achieved by a one-step filtration method, with a flux of 5900 L m⁻² h⁻¹, and separation efficiencies of 99.7 % and 98.6 %, respectively. The stability and efficiency of combining Cu-MOF with CNT were the key factors in the separation. This study not only presents a simple and easy-to-control method for the preparation of Cu-MOF@CNT membranes, but also provides an important reference for rational design and potential applications in sustainable chemistry.