Principle of electro Adsorption in Wastewater Treatment
Salt in water treatment predominantly exists in ionic form (either positively or negatively charged). The fundamental concept of electroabsorption desalination technology is to create a static field by applying an external voltage, forcing ions to migrate towards electrodes with opposite charges, thereby concentrating them within the double layer and significantly reducing the concentration of the solution, achieving desalination of the water solution.
The electroabsorption principle is illustrated in the diagram. Raw water enters the space formed by two electrode plates from one end and exits from the other. As the raw water flows between the cathode and anode, it is subjected to the effect of an electric field. Ions in the water migrate towards the electrodes with opposite charges, where they are adsorbed and stored within the double layer. With the increasing adsorption of ions by the electrodes, the ions accumulate and concentrate on the electrode surface, achieving separation from the water to obtain purified/demineralized product water.
During the electroabsorption process, the storage and release of electricity are achieved through the adsorption/desorption of ions rather than chemical reactions, allowing for rapid charging and discharging. Moreover, as only the adsorption/desorption of ions occurs during charging and discharging, the electrode structure remains unchanged, thus the number of charge-discharge cycles is theoretically limitless.
When raw water containing a certain amount of salts passes through an electroabsorption module composed of high-performance electrode materials, ions are stored in the double-layer on the electrode surface under the action of a direct current (DC) electric field until the electrode becomes saturated. At this point, the DC power supply is removed, and the positive and negative electrodes are short-circuited. Due to the disappearance of the DC electric field, the ions stored in the double-layer return to the channel and are carried away with the water flow, thereby regenerating the electrode.
Due to the electro adsorption process primarily utilizing the force of the electric field to separately adsorb anions and cations to different electrode surfaces, forming a double electric layer, this significantly reduces the concentration product of insoluble salt ions on the same electrode surface, effectively preventing the occurrence of scaling. Additionally, the water flow between the electro adsorption plates is tangential to the plates, which is不利于 the growth of insoluble salt crystals on the plates. Electro adsorption can operate in a supersaturated state of insoluble salts in concentrated water. Furthermore, within the electro adsorption module, the production of effluent with a higher hydrogen ion content due to the unbalanced adsorption of anions and cations during the process is addressed by reversing the electrodes. The slightly acidic effluent can also dissolve off any minor scaling phenomena.
The effectiveness of the electrostatic adsorption module largely depends on the adsorption performance of the electrodes.
