Study On The Preparation And Performances Of Biochar

With the rapid development of the industrialization,the dramatic increase of the world population as well as the constant consumption of fossil fuel,problems such as resource shortage and environmental pollution are on the rise.Therefore,developing clean,efficient and renewable resources and converting them into environmental protection materials are effective methods to solve these crises.As a kind of renewable resources,biomass has abundant reserves.The carbon material derived from biomass(biochar)has been paid extensive attention from researchers all over the world owing to its rich sources,low cost and environmental friendliness.The biochar has been utilized in the fields of catalyst carriers,soil conditioners,electrode materials for energy storage devices and adsorbents,wherein the latter two applications have been studied most widely.For one thing,novel energy storage device with the advantages of environmental protection and sustainability are of great intriguing interests nowadays,and its performances are mainly influenced by the electrode materials.For another,it is essential for the treatment of industrial and medical wastewater to develop new efficient adsorbents.Based on this,porous carbon material was prepared by employing the corn straw as the carbon source and applied as supercapacitor electrode material as well as adsorbent for Cr(VI)in this study.The main achievements are as follows:(1)The porous carbon(PC)was synthesized from corn straws using KOH as the activation agent.The porous structure and graphitization degree were controlled by changing the activation ratio(the mass ratio between KOH and the reactant).Scanning electron microscope(SEM),automatic specific surface and porosity analyzer,X-ray diffraction analyzer(XRD),Raman spectroscope and infrared spectroscope(FTIR)were used to characterize the physicochemical properties such as surface morphology,specific surface area,pore size distribution,crystal structure and surface functional groups.The best activation ratio was determined.The as-prepared PC possessed rich pore structure with the co-existence of micropores,mesopores as well as macropores.The specific surface area and pore volume of PC could reach to 1228.77 m~2/g and 0.77 cm~3/g respectively,when the activation ratio was1:1.(2)The supercapacitor electrode was prepared using PC as electrode material.Cyclic voltammetry(CV),galvanostatic charge-discharge and electrochemical impedance spectroscopy(EIS)measurements were carried out in 6 M KOH electrolyte and standard three-electrode system to analyze the influence of material structure on electrochemical performances.The PC with the activation ratio of 1:1 had the largest specific capacitance of285 F/g at a current density of 0.5 A/g.At high current density(10 A/g),the carbon electrode showed excellent cycling stability,and 91%of the specific capacitance was still retained after2000 times of charge and discharge cycle.(3)The adsorption performance of PC for heavy metal ion Cr(VI)was studied.The adsorption balance could be achieved at 6 h,when the solution pH was 2,the concentration of Cr(VI)was 100 mg/L and the amount of PC was 0.015 g.The adsorption type of PC for Cr(VI)was chemical adsorption and monolayer adsorption by the analyses of pseudo second-order model and Langmuir model.The theoretical saturated adsorption capacity was 175.44 mg/g.The PC prepared in this study possessed a high specific surface area and a great application potentiality in the fields of supercapacitor electrode material and wastewater treatment.This study provided a simple and effective solution for the reasonable utilization of corn straw and other waste biomass,which may achieve remarkable economic and social benefits.