| Reed is a widely distributed herbaceous plant with high biomass,short growth cycle,and strong regeneration ability,and is used in applications such as reed paper making.However,with the implementation of a series of ecological and environmental protection regulations,the use of reeds for papermaking has been banned,resulting in unharvested reeds rotting in the wetlands,decaying and depositing,clogging and silting the lake bottom and river channels,and leading to the shrinking water storage in Dongting Lake and the gradual loss of its ecological regulation function.Therefore,it is crucial to find a way to fully utilize reeds in a green way.In this experiment,reed biochar and activated carbon were prepared from reeds in Dongting Lake and their adsorption properties were investigated.The main research contents and results are as follows:(1)The reed activated carbon was prepared by high temperature activation of KOH using reed as raw material.The optimal conditions for the preparation of the optimal reed activated carbon were determined by adsorption tests,and the optimal reed activated carbon was characterized.The best adsorption performance of reed activated carbon for methylene blue was 474.87 mg/g(134.9 times higher than that of reed biochar without KOH activation)at a preparation temperature of 700℃,a KOH mass concentration of 20%,and a reaction time of 3 h.The adsorption process was able to match the Langmuir isothermal adsorption curve(R2=0.9820)for better fitting,and the secondary kinetic adsorption curve(R2=0.9808)could better describe the kinetic process of adsorption of methylene blue by reed activated carbon.The results of IR spectral analysis indicated that amide groups were generated in the prepared activated carbon.The BET specific surface area of the reed activated carbon prepared under the optimal process was 1183.40 m2/g(147.9 times that of the reed biochar without KOH activation),with a total pore volume of 0.59 m3/g and an average pore size of 2.00 nm.(2)The reed biochar was prepared by high-temperature calcination using reed as raw material and specific capacitance as the target parameter.700℃ was determined as the optimum temperature for the preparation of reed biochar through electrochemical performance tests,and the specific capacitance of the reed biochar prepared under this condition was 3.16 F/g at a current density of 0.5 A/g.The obtained reed biochar was further tested for doping with different elements,and the doped The reed biochar composites were prepared by varying the ratio of reed biochar to the material by doping with nitrogen-containing substances(urea-formaldehyde resin,melamine),metal salts(magnesium chloride,cobalt chloride)and sulfide(sodium sulfide).When the ingredient ratio of sodium sulfide to reed straw powder was 3:7,the best specific capacitance results were obtained for the prepared C700-30S electrode,whose specific capacitance was 137.59 F/g at a current density of 0.5 A/g(43.5 times the specific capacitance of the C700 sample);the current density increased from 0.5 A/g to 10 A/g with a multiplicative performance of 80.1%;the The energy density was 19.11 Wh/kg and the power density was 254.12 W/kg at a current density of 0.5 A/g;the initial specific capacitance was still 97.9%at a current density of 5 A/g with 2000 cycles of charge and discharge;the BET specific surface area was 475.32 m2/g(59.4 times that of C700),the total pore volume was 0.30 cm3/g,and the average pore diameter was 2.49 nm.(3)The reed activated carbon was prepared by high-temperature calcination with KOH activation using reed as the raw material and specific capacitance as the target parameter.The optimum preparation temperature and KOH mass concentration were determined to be 600℃ and 20%by electrochemical performance tests.Under these conditions,the obtained reed activated carbon was further tested for doping with different elements.Nitrogen-containing substances(urea-formaldehyde resin,melamine),metal salts(magnesium chloride,cobalt chloride)and sulfide(sodium sulfide)were selected for the test,and reed activated carbon composites were prepared by changing the ratio of reed activated carbon to materials.The best specific capacitance results of the prepared AC600-20K-30S electrode were obtained when the ingredient ratio of sodium sulfide to reed straw powder was 3:7.Its specific capacitance was 204.44 F/g at 0.5 A/g current density,which was 64.7 times that of C700 and 1.1 times that of AC600-20K;the current density increased from 0.5 A/g to 10 A/g with a multiplicative performance of 87.9%;the energy density was 28.39 Wh/kg and the power density was 299.72 W/kg at a current density of 0.5 A/g The BET specific surface area is 1132.69 m2/g(141.6 times that of C700 and 1.9 times that of AC600-20K),the total pore volume is 0.64 cm3/g,and the average pore diameter is 2.21 nm.In this paper,reed carbon materials with high specific surface area and good adsorption and electrochemical properties were constructed from reeds.On this basis,the effects of doping with nitrogen-containing substances(urea-formaldehyde resin,melamine),metal salts(magnesium chloride,cobalt chloride)and sulfide(sodium sulfide)on the electrochemical properties of reed carbon materials are discussed,and the doping mechanism of reed carbon electrode materials is analyzed in depth.It provides research ideas for the rational green use of reed and other biomass resources. |
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