Preparation,Surface Modification And Performance Study Of Activated Carbon Based Thin-film Capacitive Deionization Electrodes

Capacitive deionization is a kind of technology which makes the ions of brackish water adsorb to the surface of electrode material,thus forming the electric double layer.Its working principle is that when a dc voltage is put on,the ions in the solution move to the electrode plates which arises from the electric field formed by the power supply.And the ions are adsorbed on the electric double layer closely so that the aim of desalination is achieved.When the adsorption becomes saturation and the power supply is removed,ions adsorbed will leave the surface of the electrode and go back to the solution.This process is called electrode regeneration.If the power is put on again,the next cycle of adsorption can start again.The properties of the electrode material is the key factor to the CDI performance.For example,specific surface area,uniform pore size distribution and high specific capacitance are all beneficial to electrosorption.Activated carbon has the advantages of high specific surface area and low production cost and has been widely used in capacitive deionization electrode materials.However,its low mesoporous distribution and asymmetrical distribution of pore diameter limits its further development in the field of capacitive deionization.In this work,modified activated carbon composites with other materials are rolled into thin-film electrode by the method of roll-to-roll with the help of PTFE.A good CDI performance is obtained by employing the as-fabricated electrodes.The main research content of this article is as follows:(1)First,commercial activated carbon powder is modified by high-concentration KOH solution under the nitrogen atmosphere.A small amount of PTFFE and different proportions of graphene are mixed with the modified activated carbon together.The mixture is fabricated into film electrode through a roll-to-roll method.KOH solution is used to etching the commercial activated carbon so that many shortcomings of it can be overcome.At the same time,the introduction of graphene sheet can improve the electrochemical performance of the activated carbon so that the electric adsorption amount can get increased.According to the experimental results,the highest amount of absorbed ions in the modified electrodes can reach 10.5 mg/g in a 150 m L,450 mg/L Na Cl solution with a flow rate of 30 m L/min and is increased by 250% compared with that measured from the pristine activated carbon electrodes.Above results indicate a great application prospect of our electrode materials in capacitive deionization.(2)Activated carbon/polyaniline composites are prepared through in situ emulsion polymerization.In this process,the effect of the concentration of surfactant-dodecyl benzenesulfonic acid(DBSA)is investigated.After the polymerization,a small amount of PTFE is added and then the mixture is rolled into film electrode through a roll-to-roll method.The highest amount of absorbed ions measured from the electodes is 15.2 mg/g,increased by 45%,when it is compared with bare activated carbon electrodes.Great prospect is expected in the industrial application.