Preparation And Application Of Porous Carbon Microspheres Based On Poly (γ-Glutamic Acid)/Chitosan Self-Assembled Colloidal Particles

Porous carbon materials have attracted much attention because of their low density,good chemical stability and relatively good thermal conductivity.In porous carbon materials,porous carbon microspheres have a wider application prospect because of their spherical structure,which gives carbon materials higher specific surface area,adsorption properties and catalytic activity.In terms of the preparation methods of porous carbon microspheres,the traditional methods include chemical vapor deposition,hydrothermal method and template method.From the perspective of carbon precursors,the precursors to synthesize porous carbon microspheres include polymer,biomass and metal-organic framework.With the continuous improvement of the degree of industrialization,human beings gradually increase the use of fossil fuels,causing a lot of environmental pollution and ecological damage.Therefore,the study of green,environmental protection and simple preparation method is very meaningful.In this paper,a new strategy of preparing porous carbon microspheres using biopolymer colloidal particles as precursors and metal ions as crosslinking agents is proposed by using macromolecular self-assembly technology.The uses of biomass carbon precursors are diversified,and the complex synthesis process and the use of organic solvents are avoided.The specific research content and results are divided into the following two parts:（1）Preparation and application of porous carbon microspheres based on Ca²⁺/γ-polyglutamic acid/chitosan self-assembly colloidFirstly,the macromolecular self-assembly technology and high temperature pyrolysis method were combined to prepare porous carbon microspheres.The cationic polyelectrolyte chitosan（CS）and anionic polyelectrolyteγ-polyglutamic acid（γ-PGA）as self-assembly primitive,Ca²⁺as crosslinking agent,in aqueous solution through electrostatic,hydrogen bond and other weak interaction force self-assembly into colloidal particles（CS/γ-PGA CPs）,as a carbon precursor.The effect of the concentration of crosslinker on the morphology of porous carbon material and the separation of oil-in-water emulsion with porous carbon microspheres were studied.The results show that porous carbon microspheres(PCSs_0.2)can be prepared by adjusting the morphology of porous carbon materials by controlling the concentration of crosslinking agent.The separation performance of oil-in-water emulsion was studied,which can realize the rapid and effective separation of different oil droplets from water.The separation efficiency of 10 cycles is 93.8%,and the adsorption capacity is as high as 3127.43 mg·g^-1.It is further confirmed that PCSs_0.2 has good cyclic performance.The results of kinetic,isotherm and thermodynamic studies show that the adsorption behavior of PCSs_0.2to oil phase conforms to the pseudo-second-order kinetics and Langmuir adsorption isotherm model,and the process is a spontaneous and endothermic single layer chemisorption process.（2）Preparation and application of porous carbon microspheres based on Ni²⁺/γ-polyglutamic acid/chitosan self-assembly colloidIn order to prepare highly graphitized,hollow porous carbon microspheres（GHCSs）,we developed a simple and easy synthesis method of biobased GHCSs using crosslinked CS/γ-PGA CPs as carbon precursor and Ni²⁺as catalyst,crosslinking agent and template agent.The results show that high graphitized and superhydrophobic mesoporous carbon spheres can be prepared successfully by adjusting the morphology of porous carbon microspheres materials by changing the cross-linking agent of metal ions and controlling the concentration of the cross-linking agent.The performance of GHCSs for separating oil-in-water emulsion was studied.The superhydrophobic carbon material could be used to achieve rapid and effective separation of different oil droplets from water.The final separation efficiency remained at 98.1%through 10 cycles,and the adsorption capacity was still up to 3186.72 mg·g^-1,which further confirmed that GHCSs material has good cycling performance.The results of kinetic,isotherm and thermodynamic studies show that the adsorption behavior of GHCSs to oil phase conforms to the pseudo-second-order kinetics and Langmuir adsorption isotherm model,and the process is a spontaneous and endothermic single layer chemisorption process.