| In order to achieve the goal of carbon peaking and carbon neutrality,there is an urgent need to develop clean biomass renewable alternative energy The conversion of biomass waste into biochar through pyrolysis is a high value-added resource pathway.However,biochar prepared by pyrolysis alone has a limited specific surface area and a single pore size distribution,leading to a limitation of its application potential.The template method is a method that the template agent co-pyrolysis with biomass,play the template effect in the subsequent high temperature carbonization,and promote the formation of rich pore structure.The template method can effectively control the pore size distribution of biochar.But the effect of template material is influenced by various factors such as the source of template material,biomass raw material composition and the corresponding carbonization process.Therefore,a targeted tamplate carbonization scheme should be adopted for different biomass raw materials.In order to achieve effective regulation based on the adaptation of the raw material to the template charring process and improvement of the physicochemical properties of biochar,the following studies were conducted to select the representative biomass of livestock and poultry manure-swine manure and lignocellulosic biomass-corn straw as raw materials,and to match the appropriate template carbonization process according to the nature of the raw materials.(1)Swine manure naturally contains inorganic substances such as CaCO3,CaO,MgO and SiO2,which can be used as in situ templates and create partial mesopores during pyrolysis,and further pore formation and expansion during activation with activators.Therefore,a simple in situ template method was used to prepare swine manure porous carbon(SMAC)in combination with conventional pyrolysis and KOH activation techniques when swine manure was used as the carbon precursor.In this study,swine manure raw material,biochar and activated carbon were acid-washed at different stages,such as after pyrolysis and after activation,respectively,as a way to control the content and the stage of action of the template material in the samples.The purpose of this study was to investigate the mechanism of in situ template action during pyrolysis and activation and its influence on the characteristics of the prepared SMACs,by comparing three preparation schemes involving different acid-washing steps.The results showed that SMACHCL prepared by acid washing at the raw material stage was rich in microporous structures,SMACPHF had the most macroporous structures with a pore size of about 50 nm,while SMACHF had more macroporous(～100 nm)pores with larger pore sizes and mesoporous(2-4 nm)pores.The specific capacitance of SMACHF reached 278 F/g at 0.5 A/g.In the adsorption test no pickling SMACNON had the highest functional group content and exhibited the highest Pb2+adsorption of 211.8 mg/g.In conclusion,the natural inorganic substances in swine manure as in situ template promoted the efficient production of porous carbon material,and the implementation of the porous carbon material pore structure and functional group content effective control through pickling step control template stage,for livestock manure biomass got suitable template carbonization scheme,and the preparation of porous carbon material has excellent energy storage and adsorption properties,has a high research and application value.(2)The main components of corn straw are lignin,cellulose and hemicellulose,which do not contain natural template substances,so exogenous template agent KMnO4 was introduced,which played the role of both activator and template agent.Therefore,torrefaction pretreatment was applied to promote the pre-decomposition of biomass components and KMnO4,after which the activation and templating effects of KMnO4 were fully utilized in combination with high-temperature carbonization process,and finally the porous carbon material with developed mesoporous structure was produced by acid washing to remove residual impurities Meanwhile,in this study,torrefaction and carbonization products with different weight loss rates and TSI were obtained by controlling factors such as KMnO4 content in raw materials,biomass composition,torrefaction temperature and torrefaction time,and a linear relationship was established between torrefaction product TSI and carbonization product pore structure parameters to investigate the effects of changes in these factors on the regulation of carbonization product properties.The results showed that TSI correlated well with specific surface area,mesoporosity,pore volume and average pore size,and the overall R2 values were higher than 0.9.The mesoporous carbon prepared under different raw material compositions and torrefaction conditions had a wide distribution of pore structure characteristics(specific surface area:1038.62 m2/g-2115.48 m2/g;pore volume:0.89 cm3/g-2.50 cm3/g;mesoporosity:42.1%-78%;average pore size:3.16-5.85 nm).And CSC300-60-1.5 exhibiting the most excellent specific capacitance properties(389 F/g).In conclusion,by simply torrefaction pretreatment promoted the activation and template effect of KMnO4 in the process of carbonization,and realize the high quality biomass mesoporous carbon efficient production,and by changing the torrefaction process and raw material composition to realize the effective regulation of carbon material pore structure.The first established the TSI and pore structure parameter correlation theory,realize the effective prediction of carbon product pore structure. |
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