Effect Of Preparation Technology On Physicochemical Properties And Stability Of Caragana Korshinskii

China ’s annual agricultural wastes,such as straw,are as high as 700 million tons,of which about 70%are used for industrial raw materials,animal feed,soil and fertilizer,etc.However,about 200 million tons are still not fully utilized every year and are burned Disposal at will not only causes waste of resources,but also produces a certain amount of pollution to the environment.The preparation of agricultural and forestry wastes into biochar and activated carbon materials,as adsorbents to adsorb harmful gases in the air,heavy metals and organic matter in sewage,and pesticide residues in soil,is one of the effective ways to solve the reuse of agricultural solid waste.During the preparation of biochar materials,due to the differences in the structure of various types of biomass raw materials and the preparation process,the resulting biochar and activated carbon materials have very different adsorption properties.In view of this,choose Caragana biomass with local characteristics as raw materials,prepare biochar materials under two different process conditions,study its structure and performance,and provide basic experimental support for the full utilization of agricultural and forestry wastes and the production of high-quality adsorbent materials.In this paper,by using Caragana as a raw material,based on the previous group test,the carbonization and activation temperature and the flow rate of the activated gas are variables,compared with the conventional process carbonization conditions（slow heating,no activation）and CO₂ activated carbonization one-step method The specific surface area and adsorption performance of carbon materials were studied by using characterization methods such as yield calculation,industrial analysis,BET,FTIR,etc.to study the physical and chemical characteristics of Caragana biochar prepared under different processes.The results show that:（1）With the increase of pyrolysis temperature,the carbonization degree of biochar prepared by conventional process carbonization gradually increases from the low temperature drying stage to 500 ℃.The C content of the biochar gradually increases,the H and O content gradually decreases,and the N content almost changes Not big.Biochar yield and volatile content decrease,ash content and fixed carbon ratio increase,the aroma of biochar gradually increases.When the pyrolysis temperature is 500 ℃,the yield under the optimal process is 32.93%,the ash content is 15.03%,the volatile content is 17.61%,and the fixed carbon is 67.36%.The surface functional groups of biochar measured by Fourier infrared spectroscopy are generally more at low temperature.With the increase of carbonization temperature,hydroxyl and alkyl groups disappear or degrade,and carboxyl groups and aromatic carbon C-H increase.The conventional process of Caragana biochar carbonization pyrolysis temperature at 600 ℃ the best stability.In the biochar physical and chemical indicators,fixed carbon is directly proportional to stability,while H / C,O / C,volatile matter is inversely proportional to the stability of Caragana biochar.（2）As the pyrolysis temperature increases,the biochar produced by the one-step CO₂ activated carbonization process has a rapid decline in yield,especially at 800 ℃.The ash content and fixed carbon content also increased with increasing temperature,while the volatile content gradually decreased,and the specific surface area was much higher than that of unactivated biochar,reaching 176.6285m² / g.The one-step CO₂ activated carbonization process has the best stability at 800 ℃.At low temperature（<700 ℃）,biochar is mainly pyrolysis reaction.The CO₂ atmosphere only provides an inert atmosphere.At the pyrolysis temperature of 600 ℃,the biochar reaction consumption rate is affected by pyrolysis and gasification.（3）The specific surface area of the Caragana biochar prepared by carbonization in the conventional process reaches 146.5849m² / g,and the specific surface area of the Caragana biochar through the high temperature carbonization and activation treatment at 700 ° C with 500 ml of CO₂ reaches 176.6285m² / g,indicating The one-step process of CO₂ activation carbonization has a significant effect on the structure and properties of biochar.Comparing the physical and chemical indicators of biochar prepared by conventional process carbonization and CO₂ activated carbonization one-step method,the results show that the biochar after CO₂ activation has lower ash content,higher fixed carbon,more complex pore structure,larger specific surface area and pores Compared with the volume,the pore size of biochar prepared by CO₂ activation is smaller.