Study On The Preparation And Capacitive Deionization Performance Of Functional Carbon-based Nanomaterial

With the speeding of industrialization and increasing of population, the shortage of water sources has become obvious. Besides, the pollution of the environment and warming of the climate make that wose. Most countries pay more attention to desalination technology due to the advantages of large reserves and widespread. Capacitive deionization (CDI), also called electrosorption, which removes the charged species from solution by electrostatic field formed between porous electrode and solution interface. Basically, CDI efficiency is closely related to the characteristics of the electrode’s material, such as specific surface area, conductivity, etc. In this case, carbon-based materials owning advantages of high chemical inertness, high specific surface area, controllable pore size and conductivity have been widely utilized. Hence, in this thesis, we proposed some functional carbon-based nanomaterials containg oxidation activated carbon (AC), TiO2 @ carbon nanotubes (CNTs) composites and carbonization zeolitic imidazolate framework-8 (ZIF-8) as electrodes for CDI. The preparation and electrosorption mechanism have been comprehensively investigated. Specifically, the main research contents are given as blow.1. The Functional activated carbon (FAC) involving a large number of hydroohilic groupshas been prepared via hydrothermal oxidation approach. By compared to pristine AC, FAC shows decreased surface area and improved microspores volume. Further, the electrochemical analysis shows that the specific capacitance of FAC was 232 F·g-1 which has been raised 6% as against AC’s (219 F·g-1) at the scan rate of 1 mV·s-1. Through calculating the respective capacity, it is found that the improved double layer capacity is accounting for the increased specific capacity. Regarding to CDI performance, the maximum electrosorption capacity of FAC electrode was 3.54 mg·g-1. On the other hand, the FAC electrode followed the Langmuir isotherm. Besides, the pseudo-first order can describe the electrosorption kinetics of FAC electrode. Moreover, after three cycles of adsorption-desorption, there is no decay on electrosorptin capacity, implying the superior regeneration.2. The TiO2@ CNTs with mass ratios of 1,2.5,5 have been prepared by sol-gel method (labeled as TiO2@CNTs-1, CNTs-2, CNTs-3). It is observed that anatase TiO2 particles with diameter of 15 nm can attached onto the CNTs tubes very well. The electrochemical analysis exhibits that the specific capacitance of TiO2@CNTs-1 (111.26 F·g-1) is three times higher than that of the CNTs’(35.15 F·g-1). Further, with the loading increases, the pressure drop, contact resistance and diffusion resistance increase which is harmful for electrosorption. Utilizing TiO2@CNTs-1 as electrode, it is found that the maximum electrosorption capacity was 4.08 mg·g-1 and the TiO2@CNTs-1 electrode followed the Langmuir isotherm, indicating the monolayer adsorption. Besides, the pseudo-first order can describe the electrosorption kinetics of TiO2@CNTs-1. Besides, the excellent regeneration performace of TiO2@CNTs-1 electrode has been demonstrated.3. The porous carbon material (PCP) has been prepared by carbonization zeolitic imidazolate framework-8 (ZIF-8) at high temerature. The resultant PCP containg huge micro and mesopores is an amorphous carbon. The specific surface area and pore volume of PCP were 1122.19 m2·g-1 and 0.697 cm3·g-1, respectively. The electrochemical analysis illustrates that the specific capacitance of PCP electrode was 166.34 F·g-1 at the scan rate of 1 mV·s-1. Furtherm, the CDI results show that the maximum electrosorption capacity of PCP was 2.41mg·g-1 and the PCP electrode followed the Langmuir isotherm, implying the monolayer adsorption. Besides, the pseudo-first order can describe the adsorption kinetics of PCP electrode. Finally, the superior regeneration performance of PCP electrode has been proved.