Preparation Of Peanut Shell Based Carbon Materials And Their Adsorption Properties For Methylene Blue

Biomass is a renewable carbon source that exists in nature.Making full use of biomass to produce high-performance carbon materials is of great benefit to China’s carbon reduction cause.Using hydrothermal carbonization method to generate nitrogen doped hydrothermal carbon in one step,and then utilizing steam activation technology to prepare high application value while maximizing environmental protection and energy conservation.The main research content of this article is as follows:Nitrogen doped porous carbon was prepared in one step by hydrothermal carbonization using peanut shell,a typical representative of biomass,as the carbon source and low concentration ammonia water as the nitrogen source.Using the adsorption performance of methylene blue as the evaluation standard,the effects of hydrothermal reaction temperature(160,200,240℃),reaction time(2,6,10 h),and ammonia addition amount(0,50,100,150,200 mL)on the adsorption performance of peanut shell based nitrogen doped hydrothermal carbon for methylene blue were investigated.The results showed that the best material for adsorbing methylene blue was PSC200-6,and the preparation process parameters were:hydrothermal reaction temperature of 200℃,reaction time of 6 h,and ammonia addition of 100 mL.The peanut shell based nitrogen doped hydrothermal carbon prepared under this condition has a adsorption capacity of 39.403 mg·g-1 and an adsorption rate of 98.861%for a 100 mg·L-1 methylene blue solution.It is 2.824 times the adsorption capacity of undoped nitrogen atoms on hydrothermal carbon under the same adsorption reaction conditions.In the experiment of peanut shell based nitrogen doped hydrothermal carbon adsorbing methylene blue,the effects of the amount of peanut shell based nitrogen doped hydrothermal carbon added,the initial concentration of methylene blue,and the adsorption reaction temperature and time on the adsorption effect were investigated.The results showed that the optimal addition amount of peanut shell based nitrogen doped hydrothermal carbon was 0.1 g,the initial concentration of methylene blue was 100 mg·L-1,the adsorption temperature was 30℃,and the adsorption time was 24 h.And characterize carbon materials with excellent adsorption performance by using techniques such as BET and FT-IR.The results indicate that ammonia water can effectively modify carbon materials to have more functional groups and defect structures on their surfaces.To analyze its adsorption mechanism,adsorption kinetics simulation and isothermal adsorption experiments were conducted on it.The results showed that the adsorption of methylene blue on peanut shell based nitrogen doped hydrothermal carbon was more in line with the Lagergren quasi second order kinetics model(R2=0.99988),and the adsorption rate was mainly affected by the chemical adsorption process.The isothermal adsorption simulation conforms to Langmuir’s isothermal adsorption model(R2≥0.99586),and the adsorption process of methylene blue is monolayer adsorption controlled by chemical adsorption.Water vapor activation can effectively improve the adsorption performance of peanut shell based nitrogen doped hydrothermal carbon.Using the adsorption of methylene blue as the evaluation standard,PSC200-6 with excellent adsorption performance in the previous chapter was selected as the raw material.Orthogonal experiments were conducted to investigate the effects of activation reaction temperature,time,and water vapor flow rate on the adsorption effect of steam activated modified peanut shell based nitrogen doped hydrothermal carbon.The results show that the order of influence of three factors on adsorption efficiency is:activation reaction time(B)>water vapor flow rate(C)>activation temperature(A).The preparation process of HAC133 with the best adsorption performance is as follows:activation temperature is 750℃,reaction time is 1.5 h,water vapor flow rate is 0.06 mL·(g·min)-1,and the adsorption capacity for a 100 mg·L-1 methylene blue solution is as high as 131.693 mg·g-1,with an adsorption rate of 99.427%.The adsorption capacity of activated modified carbon materials for methylene blue is 1.49 times that of carbon materials treated at high temperature but not modified by steam,and 9.438 times that of non activated peanut shell based nitrogen doped hydrothermal carbon.In the experiment of water vapor activation modified peanut shell based nitrogen doped hydrothermal carbon for adsorption of methylene blue,the effects of the addition amount of activated modified peanut shell based nitrogen doped hydrothermal carbon,the initial concentration of methylene blue,and the adsorption reaction temperature and time on the adsorption effect were investigated.The results showed that the optimal amount of nitrogen doped activated carbon modified by steam activation was 0.03 g,the initial concentration of methylene blue was 100 mg·L-1,the adsorption reaction temperature was 30℃,and the adsorption time was 24 h.By characterizing the activated modified hydrothermal carbon,the use of steam activation can greatly increase the specific surface area by 91.296 times,effectively increasing the total pore volume and pore size,containing rich functional groups and defects.The adsorption kinetics and isothermal adsorption experiments of activated peanut shell based nitrogen doped hydrothermal carbon were simulated,indicating that the adsorption of methylene blue by activated peanut shell based nitrogen doped hydrothermal carbon is more in line with the Lagergren quasi second order kinetics model(R2=0.99983),and the adsorption rate is mainly controlled by chemical adsorption.The isothermal adsorption simulation conforms to Langmuir’s isothermal adsorption model(R2≥0.98237),and the process of vapor activated modified peanut shell based nitrogen doped hydrothermal carbon adsorption of methylene blue is mainly monolayer uniform chemical adsorption.