Popcorn Based Dio-porous Carbon Materials And Their Applications In Capacitive Deionization

Capacitive deionization(CDI)is a low energy consumption and environmentally friendly desalination technology,which has become the focus of researchers.Electrode materials are the focus if capacitive deionization technology and play a key role in desalination process Compared with the traditional CDI electrode materials such as graphene and carbon nanotubes.biomass have the advantages of low cost,abundant resources and green regeneration.In addition,the reuse of biomass waste can protect the environment.Therefore,it is of great significance to study effective and practical biomass material for promoting the development of CDI electrodes.In this paper,low cost and wide source of biomass-corn as carbon source,microwave and chemical activation combined with two different chemical activators(KHCO3 and KOH)to prepare popcorn porous carbon material,and prepared it as CDI electrode,to study the performance of popcorn porous carbon electrode in the process of capacitive deionization.Based on the above content,the main contents and achievements of this paper are as follows:1.Synthesis and properties of KHCO3 activated popcorn porous carbonCorn is prepared into three-dimensional flocculation porous carbon(PPC-KHCO-X,which X represents activation temperature)by microwave expansion and activation of KHCO3.The specific surface area and pore volume of PPC-KHCO increases with the increase of activation temperature,and PPC-KHCO-850 has the largest specific surface area(2084 m2 g-1)and pore volume(0.974 cm3g-1).Due to the activation of KHCO3,PPC-KHCO shows three-dimensional flocculent porous structure,and PPC-KHCO-800 has the most complete structure.The three-dimensional flocculent porous structure was conducive to the transport of protons and ions.The presence of O element and a small amount of N element in PPC-KHCO-800 can increase the pseudo capacitance of the material and improve the wettability of the material.PPC-KHCO shows approximately rectangular characteristics in the cyclic voltammetry test,showing good capacitance,and PPC-KHCO-800 has the highest specific capacitance of 117 F g-1,which has the potential to be used as CDI electrode material.In view of the above characteristics of the material,PPC-KHCO was prepared as CDI electrode for desalination experiment.The electric adsorption capacity of PPC-KHCO-800 electrode is 10.11 mg g-1,which is the maximum in PPC-KHCO.2.Synthesis and properties of KOH activated popcorn porous carbonCorn is prepared into two-dimensional sheets of porous carbon(PPC-KOH-X,where X represents activation temperature)by microwave expansion and KOH activation.With the increase of temperature,the specific surface area and pore volume of PPC-KOH increase,and the pore structure of PPC-KOH change from microporous structure to mesoporous structure PPC-KOH-850 has the largest specific surface area(2970 m2 g-1)and pore volume(1.744 cm3 g-1),and PPC-KOH-750 has the highest micropore specific surface area(976 m2g-1).Due to the etching action of KOH,PPC-KOH shows a rough porous two-dimensional sheet structure.The rough porous surface can greatly improve the specific surface area of the material,which is conducive to the adsorption of ions.PPC-KOH-750 has abundant O element and a small amount of N element,which can increase the pseudo capacitance and improve the wettability of the material.PPC-KOH shows approximately rectangular characteristics in the cyclic voltammetry test,and had good capacitance and potential as CDI electrode material.The capacitance of PPC-KOH-750 is 148 F g-1,which is the maximum in PPC-KOH-750,and the microporous characteristics of PPC-KOH-750 are the reasons for its high capacitance.In view of the above characteristics of the material,PPC-KOH is prepared as CDI electrode for desalination experiment.The electric adsorption capacity of PPC-KOH-750 electrode is 14.25 mg g-1,which is the maximum in PPC-KOH.3.Comparison of the properties of KHCO3-activated and KOH activated popcorn porous carbon materialsThe porous carbon materials prepared by the activation of KHCO3 and KOH with the same activation temperature and proportion have different physical and activation properties The results of scanning electrode(SEM)and transmission electron microscope(TEM)show that PPC-KHCO is a three-dimensional flimsy porous structure,and PPC-KOH is a two-dimensional lamellar porous structure.Nitrogen adsorption and desorption tests show that the specific surface area and pore volume of PPC-KOH are lager than that of PPC-KHCO.According to X-ray photoelectron spectroscopy(XPS)analysis,PPC-KOH-750 has higher O content than PPC-KHCO-800,and the abundant O functional groups are beneficial to improve the pseudo capacitance and wettability of the material.Compared with the electrochemical characteristics of the two materials,the specific capacitance of PPC-KOH is greater than that of PPC-KHCO.The adsorption capacity of PPC-KOH electrode is also greater than that of PPC-KHCO electrode when the two materials are used in capacitive deionization experiments.This study shows that the KOH activated popcorn porous carbon material has high specific surface area and large pore volume,so it has a high specific capacitance,showing a good electrical adsorption capacity.However,PPC-KHCO is preferred as CDI electrode material in this paper because of the enhanced corrosion properties of KOH activator,which is easy to cause loss to experimental equipment.4.The condition exploration of popcorn porous carbon for capacitive deionization technologyThe operating parameters of capacitive deionization process were optimized.The optimal operating parameters are as follows:operating voltage is 1.2 V,liquid flow rate is 20 mL min-1,and liquid concentration is 500 mg L-1.PPC-KHCO-800 electrode has a good recycling property.After five desalination times,its electro-adsorption capacity remains 86% of the original.