The Preparation Of Layered Metal Compounds And Its Application In Capacitive Deionization

Because of the growth of world's population,economic development and increasing environmental pollution,the demand for fresh water is growing.So people pay more attention to the solution to obtaining cheap fresh water from seawater which cover 97% total water resource.Nowadays,common desalination technology mainly includes distillation,reverse osmosis and electrodialysis.However,these methods have the weakness of high energy consumption and secondary pollution.Capacitive deionization(CDI)based on the principle of electric double layer has caused wide attention in recent decades due to its advantages of low energy consumption,high efficiency,environmental friendly.Electrode material is the core of CDI technology whose choice determines the performance of desalination and cycle stability.Layered double hydroxide(LDH),as a two dimensional nano material,has the charactiristic of low cost,high redox reactivity and environment friendly,which provide a new direction for the development of CDI electrode materials.This paper focuses on the preparation of layered metal compounds and its application in CDI.Meanwhile,the paper explores the structure and deionization performance of magnesium aluminum metal oxide/graphene composite,the main contents are as follows:(1)Layered double hydroxides(LDHs)were obtained by urea-hydrolyzed hydrothermal reaction.On heating in N2,LDHs were converted to corresponding oxide.The prepared MgAl-Ox was used as anode of CDI cell.AC(Activated Carbon)and the AC acidized by nitric acid were used as cathode,respectively.The CDI tests shows that as prepared asymmetric cell exhibited excellent cycling stability whose adsorption capacity kept around 2.4 mg g-1 after 40 cycles.The method to treat activated carbon with nitric acid(AC-HNO3)to introduce carboxyl groups which effectively avoid the co-ion expulsion effect.Adsorption capacity of MgAl-Ox//AC-HNO3 cell kept around 5 mg g-1 after 40 cycles.(2)The introduction of graphene enhanced the material conductivity and improved the migration rate of charge effectively.Porous MgAl oxide/graphene hybrids(MgAl-Ox/G)were prepared by a friendly one-step hydrothemal method and calcination under N2 atmosphere.The material with three-dimensional porous structure enhanced the conductivity and reduced the reunion of graphene.Desalination test was conducted under the supply voltage of 1.0/-1.0 V with the asymmetric cell which assembled with MgAl-Ox/G as anode and AC-HNO3 as cathode.Adsorption capacity of the asymmetric cell can reach 13.6 mg g-1.The study of process parameter showed that when calcination temperature was 400 ? and graphene content was 10%,the sample exhibited optimal performance.