Study On The Structure And Performance Of Bamboo Shoot Activated Carbon

Activated carbon materials derived from biomass has the developed pore structures,high specific surface area and abundant chemical functional groups and other unique features,which makes it widely used in the fields of adsorption,catalysis,energy storage and so on.As the bud of bamboo,bamboo shoot has a special growth pattern than other plants.In this study,bamboo shoot was used as raw material,relying on the unique multi-lamellate structure and chemical composition of cell wall,the nitrogen-containing compounds of bamboo shoot as the nitrogen source,and KHCO₃ as the activator to synthesize nitrogen-doped bamboo shoot activated carbon via an in-situ synthesis method.By adjusting the preparation process to optimize its pore structure and surface properties,investigate its adsorption performance on methylene blue and carbon dioxide,its catalytic performance in Knoevenagel condensation reaction and transesterification reaction and the electrochemical performance in lithium ion batteries.To establish the relationship of bamboo shoot activated carbon materials among component-structure-performance.To clarify the essential reason,mechanism and regulation law between bamboo shoot activated carbon material's pore tuning,nitrogen atom doping and its performance.The relationship of composition,structure and property of activated carbon of bamboo shoot was investigated to find the synergy of components.The results of this research will be of great theoretical signification to develop the new type of activated carbon of bamboo shoot.The main conclusions were as follows:(1)The yield of activated carbon derived from bamboo shoot was lower than that of direct carbonized samples.The higher the activation temperature and the greater the amount of activator,the lower the yield.It was found that the nitrogen content of bamboo shoot was higher than that of mature bamboo,and the nitrogen content of activated carbon of bamboo shoots was lower than that of direct carbonized samples.BSNC-600-4(activation temperature was 600?,mass ratio of KHCO₃ to bamboo shoot was 4:1)had the highest nitrogen content,reaching 4.65 wt%;BSNC-800-4(activation temperature was 800?,a mass ratio of KHCO₃to bamboo shoot was 4:1)had the lowest nitrogen content,only 1.06 wt%.The nitrogen-containing functional groups in bamboo shoot activated carbon existed in the form of pyridine nitrogen,pyridone nitrogen,quaternary nitrogen and nitrogen-oxide,quaternary nitrogen had the best stablity at high temperatures.There were chemical functional groups such as C-H,C=O,and-N=N-in them.Bamboo shoot activated carbon materials had hierarchical pore structures ranging from micropores to mesopores to macropores.The average pore size of the activated carbon was concentrated around 2 nm,mainly micropores and mesopores.BSNC-800-4 had the largest specific surface area and pore volume,2270.9 m²/g and 1.25 m³/g,respectively.Bamboo shoot activated carbon materials had an amorphous form and a certain degree of graphitization.The activation process of bamboo shoot activated carbon materials by KHCO₃ was inferred.(2)Based on the adsorption performance of bamboo shoot activated carbon for methylene blue,the optimal preparation process was an activation temperature of 800?and a mass ratio of KHCO₃ to bamboo shoot of 4:1(BSNC-800-4).The pore structure and nitrogen doping form of bamboo shoot activated carbon had significant effects on the adsorption performance of methylene blue.BSNC-800-4's high specific surface area,large pore volume and the presence of nitrogen and oxygen functional groups worked together to make it had the best MB adsorption performance.The change of p H value affected the adsorption capacity of MB,and the proper p H of the adsorption solution was 7,and the adsorption capacity of BSNC-800-4 for MB was 310.6 mg/g.The initial concentration and contact time of MB solution had an impact on its adsorption capacity.Its adsorption process included two stages:rapid adsorption period and adsorption equilibrium period.At 25?,its equilibrium data were well fitted to Langmuir isotherm model with a maximum monolayer adsorption capacity of 458.0 mg g^-1.The pseudo-second-order kinetic model could be used to accurately estimate the carbon material's(BSNC-800-4)adsorption process.The adsorption mechanism between methylene blue solution and BSNC-800-4 was controlled by film diffusion.(3)Based on the adsorption performance of bamboo shoot activated carbon for carbon dioxide,the optimal preparation process was an activation temperature of 700?and a mass ratio of KHCO₃ to bamboo shoot of 4:1(BSNC-700-4).BSNC-700-4 had the largest adsorption capacity of CO₂ at a temperature of 273 K,1 bar and a temperature of 298 K,1 bar(6.36 mmol/g and 3.45 mmol/g,respectively),which was related to its specific surface area,total pore volume,micropore volume and the presence of nitrogen-containing functional groups.The adsorption heat of BSNC-700-4 for CO₂ adsorption was 45.70 k J/mol,mainly physical adsorption.It was found that the adsorption of CO₂ was better than that of N₂ in the gas selective adsorption test.And it had good stability when used as an adsorbent.(4)Based on the catalytic performance of bamboo shoot activated carbon on Knoevenagel condensation reaction and transesterification reaction,the optimal preparation process was an activation temperature of 700?and a mass ratio of KHCO₃ to bamboo shoot of 4:1(BSNC-700-4).After modified by potassium tert-butoxide(t Bu OK),BSNC-700-4 had the best catalytic performance for the Knoevenagel condensation reaction,and it had a good stability;BSNC-700-4 treated under this condition can also catalyze the transesterification reaction.(5)Based on the electrochemical performance of bamboo shoot activated carbon for lithium ion batteries,the optimal preparation process was an activation temperature of 700?and a mass ratio of KHCO₃ to bamboo shoot of 4:1(BSNC-700-4).The first charge and discharge capacity of the sample were 1269.4 and 690.6 m A h/g,and the coulombic efficiency was 54.4%.When the current density was 0.05 A/g,its reversible capacity was 611.3 m A h/g after 100 cycles,and the coulombic efficiency was 98.7%.The excellent electrochemical performance of BSNC-700-4 was mainly related to the pore structure,morphology and surface functional groups of the material itself.