Recent progress in developing advanced membranes for emulsified oil/water separation

Abstract

The separation of oily wastewater, especially emulsified oil/water mixtures, is a worldwide challenge because of the large amount of oily wastewater produced in many industrial processes and daily life. For the treatment of oily wastewater, membrane technology is considered the most efficient method because of its high separation efficiency and relatively simple operational process. In this short review, the recent development of advanced filtration membranes for emulsified oil/water mixture separation is presented. We provide an overview on both traditional filtration membranes, including polymer-dominated and ceramic-based filtration membranes, and recently developed nanomaterial-based functional filtration membranes, especially one-dimensional nanomaterials, for effectively treating emulsified oil/water mixtures. The liquid flux and antifouling property, which are the most important factors for membrane performance evaluation, are described for different types of membranes. Conclusions and perspectives concerning the future development of filtration membranes are also provided. Oil/water separation, especially emulsified oil/water mixture separation, has become a widespread concern because of the severe fouling problem caused by the easy adsorption of oil droplets onto the surfaces of filtration membranes. Many strategies have been employed to eliminate the fouling problem, but it remains a challenge and impedes the development of membrane technology. In this short review, we discuss the recent development of membrane technology for emulsified oil/water separation. As shown in the image, in addition to polymer- and ceramic-dominated traditional membranes, nanomaterial-based membranes have recently demonstrated their superiority and have achieved high performance. Investigating the mechanics of oil–water separation is important for developing efficient membrane filtration technologies for oily wastewater. Oil-containing effluent is produced in vast quantities — both industrially and domestically — and oil removal, particularly from emulsions, poses a significant challenge for wastewater treatment. Jian Jin and colleagues from the Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, China, review the most promising membrane filtration technologies for separating oil–water emulsions. Advancements in polymer- and ceramic-based filtration membrane technologies have improved both anti-fouling and flow rate performance. In the laboratory, ultrathin membranes based on one-dimensional nanomaterials such as carbon nanotubes show particular promise in providing high separation performance, even for surfactant-stabilized water-in-oil emulsions. With further development, nanomaterial-based membrane filter technologies have the potential to offer high-performance emulsion separation at industrial scales.