| Fresh water is essential to the survival of humans and all living things. It is precious naturalresources of industrial and agricultural production, economic development and environmentalimprovement. Recently, Shortage of fresh water resources is the global problem that we are facing.It is significant to do desalination of seawater or brine to solve the problem. So the developmentof efficient desalination technology is very important. Capacitive desalination, also calledcapacitive deionization(CDI) is a new type of electrochemical technology for water treatment.Comparing with the existing reverse osmosis and electrodialysis, CDI is getting more attention bythe researchers as a new type of desalination technology because of its low cost and no secondarypollution. Electrode material is the key of development of CDI. Carbon nanofiber is an excellentmaterial for electrode. Electrospinning is a very simple method of preparation for fiber materials.Polyacrylonitrile (PAN) has been widely used in the manufacture of CNF precursor because of itsgood spinnability and high carbon yield, and carbon nanofibers (CNF) can be obtained afterpre-oxidation, carbonization directly. However, structure performance and ion adsorption capacityof CNF electrode is not outstanding.In this thesis, ZnCl2and Zn(Ac)2was chosen as additive, to mix with PAN in DMF. Thenanofiber were electrospun with the ZnCl2/PAN and Zn(Ac)2/PAN mixture solution. The obtainedZnCl2/PAN and Zn(Ac)2/PAN fibers were pre-oxidized and carbonized. And then the ZnO-carbonnanofiber composite with ZnO homogeneous distribution were obtained due to the decompositionof the additives under the high temperature treatment. These ZnO-carbon nanofiber compositewere used as a electrode material for CDI application. The influence of different additive on theelementary composition、structure performance and additive ratio on capacitive desalination performance was investigated by energy dispersive spectrometer (EDS), X-ray photoelectronspectroscopy (XPS), transmission electron microscope(TEM), raman spectroscopy,thermos-gravimetric analysis(TGA), field emission scanning electron microscopy(FESEM),contact angle analysis and electrochemical techniques. The main research results were as follows:With ZnCl2as additive by mixing with PAN in DMF, the ZnCl2/PAN based ZnO-carbonnanofiber composite was obtained through electrospinning, followed by heat treatment while thedecomposition of ZnCl2. As a result, hydrophily and graphitization degree increase and theexisting ZnO is homogeneous distribution. The capacitor with ZnO-CNF(ZnCl2) as electrode wasassembled for capacitive deionization. The desalination performance of the capacitor wasimproved significantly. And the desalt amount has direct ratio relations with ZnO content, moreZnO, higher desalt amount. At ZnCl2proportion of2wt%, ZnO-CNF(ZnCl2) loads in the highestcontent of ZnO, which is measured by EDS. The best desalt amount of the corresponding CDI cellis8.35mg/g, current efficiency is69.89%.With Zn(Ac)2as additive by mixing with PAN in DMF, the Zn(Ac)2/PAN basedZnO-carbon nanofiber composite was obtained through electrospinning, followed by heattreatment. Uniformity of the pristine fiber is better. SEM and TEM characterize the homogeneousdistribution of ZnO on fiber suface. The capacitor with ZnO-CNF(Zn(Ac)2) as electrode wasassembled for capacitive deionization. And desalt amount has direct ratio relations with ZnOcontent, more ZnO, higher desalt amount.At Zn(Ac)2proportion of3wt%, ZnO-CNF(Zn(Ac)2)loads in the highest content of ZnO. The best desalt amount of the corresponding CDI cell is11.24mg/g, current efficiency is58.74%.To sum up, the obtained ZnO-carbon composite nanofibers with ZnCl2and Zn(Ac)2as theadditive can be used in capacitive desalination and they perform well. They are expected to beapplied to practical water desalination application. Comparing to these two materials, the obtainedZnO-carbon nanofiber composite with Zn(Ac)2as the additive get a higher desalt amount thanZnO-CNF(ZnCl2)’s... |
PDF Full Text Request