Introduction to the results
Membrane separation technology is widely used in water and wastewater treatment due to its relatively low cost, easy operation and high efficiency. However, current membranes have tradeoffs between selectivity and permeability and membrane contamination. Recently, many studies have focused on the development of high-performance carbon nanomaterials (usually carbon nanotubes and graphene) base films for water and wastewater treatment. Many studies have shown that their permeability and anti-pollution properties can be further improved with the assistance of electrochemical , thanks to the good conductivity of carbon nanomaterial base films.
This article, Dalian University of Technology QuanxieEnviron. Sci.: Nano" journal published a review titled "Carbon nanomaterial-based membranes for water and wastewater treatment under electrochemical assistance", study the latest progress in the separation process of nanocarbon plasma membrane and electrochemical auxiliary membrane . First, we summarized some methods for preparing some typical conductive films in recent years, such as carbon nanotube film and graphene film. Subsequently, potential mechanisms (e.g., electrooxidation, electrosorption, and electrostatic interactions) for electrochemically enhanced permeability selectivity, antifouling and regenerative properties are discussed, and the practical limitations of membrane/electrochemical systems are highlighted and possible solutions are outlined.
Graphics and text introduction
2.1 Motive for coupling
Figure 1. The scheme for showing the motivation for coupling membrane separation and electrochemical coupling
2.2. Electrochemical auxiliary membrane process system
Figure 2. Schematic diagram of the two-electrode system and three-electrode system of electrochemical auxiliary membrane process. Electrochemical auxiliary membrane process
2.3 Preparation of conductive nanocarbon plasma membrane
To achieve the combination of membrane separation and electrochemistry, the membrane should have excellent electrochemical properties, such as good conductivity and electrochemical stability, to allow electron transfer and long-term operation in water. Carbon materials, especially carbon nanomaterials, usually have excellent conductivity and stability due to their delocalized π electronic systems and sp2 hybrid cellular networks with strong in-plane σ bonds. Furthermore, they have atomic-level smooth surface or internal channels, or atomic-level thin structures, so they can be used to build high-performance membranes with excellent selectivity and permeability. The advantages of these membranes prompted the introduction of electrochemistry to further improve their performance and impart new functions to them.
Figure 3. Schematic diagram of some typical nanocarbon membranes and their main preparation methods
2.4. Mechanism of membrane/electrochemical integration system
Figure 4. Some mechanisms of membrane/electrochemical system: (a) electrosorption; (b) electrosorption; (c) electrooxidation; (d) electroreduction; (e) electroosmotic; (f) electrophoresis.
2.5 Improve the selectivity of carbon plasma membrane with electrochemical assistance permeability
Thanks to the above electrochemical functions, electrochemically assisted nanocarbon plasma membrane has been studied to remove various pollutants in water, such as inorganic ions, organic matter and aquatic pathogens.
Figure 5. (a) Electrofenton assisted membrane separation (b) Electrofilter-activated persulfate system (c) Electro Peroxide Auxiliary membrane separation
2.6 Application of membrane/electrochemical systems in bioelectric systems
Figure 6. A novel electrofenton membrane bioreactor (EFMBR) with enhanced processing performance (a), COD (b) and NH4 + of EFMBR -N(c) removal efficiency
summary
nanocarbon film has excellent permeability and selectivity, and can provide a platform for integrated film separation and electrochemistry, thereby realizing promising technologies for water purification and wastewater treatment, which is derived from its excellent reactivity, antifouling and self-cleaning properties. The electrochemically assisted separation process extends membrane function beyond single-hole exclusion separation. Enhanced pollutant and salt removal demonstrates their potential applications in the production of drinking and clean water from wastewater and brine.Convection-enhanced mass transfer promotes rapid degradation of organic micropollutants (electrooxidation, electroreduction and electrofenton processes) through electrochemical reactions during the flow-through membrane process. In addition, inevitable membrane contamination can be significantly reduced by electrostatic repulsion and electromotive phenomena (electroosmotic, electrophoresis, and electromigration). However, before the practical application of nanocarbon films and electrochemical auxiliary film technologies, there are still some problems that need to be solved.
In the future, efforts should be made to design large membrane components that can achieve efficient membrane filtration and electrochemical assistance. The authors believe that advances in membranes based on carbon nanomaterials can also greatly facilitate many other fields such as energy production, chemical synthesis and purification. Given the many advantages of these film and electrochemical auxiliary film technologies over traditional film processes, there is great promise in the future.
Literature:
https://doi.org/10.1039/D2EN00545J
