Study On The Preparation And Adsorption Property Of Activated Carbon From Lignite And Ulva

The resources of low-rank coal are abundant in China,and which account for more than half of coal reserves.Lignite has a low degree of coal-mineralization,high calorific value and high water content.It is a typical low-quality coal with low direct utilization efficiency.The co-pyrolysis of lignite and biomass has become one of worldwide lignite research hotspots.A large amount of pyrolysis semi-coke is piled up and idled,which not only wastes resources but also pollutes the environment.Activated carbon has the characteristics of large specific surface area,surface functional groups,etc.,which is widely used in adsorption,energy storage and other fields.High value-added activated carbon is prepared from low cost pyrolysis semi-coke,so as to greatly improve maximize the efficiency of the resource utilization of lignite and biomass.In this paper,lignite(IL)and ulva(SU)were as the main raw materials.The pyrolysis products were characterized and analyzed by GC-MS and FTIR,so as to explore the synergistic effect in the process of co-pyrolysis and optimize the pyrolysis process.Lignite-ulva-based activated carbon and ulva-based activated carbon were prepared respectively from co-pyrolysis semi-coke and ulva by using KOH.The effects of activation time,activation temperature,alkali-carbon ratio(KOH and semi-coke mass ratio)on the adsorption performance of activated carbon were investigated by the adsorption value of methylene blue and the adsorption performance of activated carbon.The single factor experiments and response surface methodology(RSM)were adopted to optimize the activation process condition.Two kinds of AC were characterized by SEM、FTIR and specific surface area analysis,so as to explore their adsorption mechanism(isothermal adsorption model and adsorption kinetic model).Under the experimental conditions of this study,the research conclusions mainly included the following aspects:(1)When the mass fraction of Dendrobium in lignite is 30%,the yield of pyrolysis oil reaches a maximum of 14.03%,which increased by 57.59%compared with that of lignite pyrolysis solely.GC-MS,FTIR,SEM and TGA results showed the synergy existed in the co-pyrolysis process.(2)The results of single factor experiments and response surface optimization experiments indicated that under the optimal conditions of mass ratio of KOH to co-pyrolysis semi-coke 2.95,activated time 59.09 min and activated temperature 812.90℃,the iodine adsorption value and methylene blue adsorption value of lignite-ulva-based activated carbon could be up to 1724.10 mg/g and 710.98 mg/g.BET specific surface area of lignite-ulva-based activated carbon was up to 1519.3m~2/g,and its microporous pore structure was rich.(3)The results of single factor experiments and response surface optimization experiments indicated that under the optimal conditions of mass ratio of KOH to semi-coke of ulva 2.99,activated time 44.47 min and activated temperature 809.91℃,the iodine adsorption value and methylene blue adsorption value of lignite-ulva-based activated carbon could be up to 1843.11 mg/g and 931.38 mg/g.BET specific surface area of ulva-based activated carbon was up to 2616.3m~2/g,and ulva-based activated carbon showed micro-and mesoporous structure.(4)The surface of the two kinds of activated carbon contains abundant functional groups such as hydroxyl groups.The adsorption mechanism models of the two kinds of activated carbon are in line with the Langmuir isothermal adsorption model and the quasi-secondary kinetic model.