Study on preparation of nitrogen-doped biochar and its adsorption properties for methylene blue
Biomass lycium chinensis stalks were used as raw materials,KHCO3 as activator,and urea as nitrogen source to explore the preparation of nitrogen-doped biochar.The morphology,structure,and surface functional groups of the produced biochar were characterized was performed using scanning electron microscopy(SEM),nitrogen adsorption-desorption instru-mentation(BET),X-ray powder diffraction(XRD),Raman spectroscopy(Raman),Fourier transform infrared spectroscopy(FT-IR),and X-ray photoelectron spectroscopy(XPS).And its adsorption behavior towards methylene blue(MB)in water was explored.The results showed that the optimal conditions for KHCO3 to activate Lycium chinensis stalks were as follows:mass ratio of 1∶2(Lycium chinensis stalks carbonized material and KHCO3),activation temperature of 800℃,and activa-tion time of 1 h.The optimal conditions for doping urea on the surface of lycium chinensis stalks biochar(LBC)were as fol-lows:mass ratio of 1∶4(LBC and urea),and nitrogen-doped biochar(LBC-N)was prepared by calcination at 800℃for 1 h.The specific surface area of LBC and LBC-N were 940.29 m2/g and 1 169.78 m2/g,the total pore volumes were 0.57 cm3/g and 0.72 cm3/g,and the average pore sizes were 5.81 nm and 3.20 nm,respectively.All of them were mainly mesoporous bio-mass activated carbon materials.Under the corresponding experimental conditions,the adsorption capacities of LBC and LBC-N for MB were 542.02 mg/g and 639.20 mg/g,respectively.The Pseudo-second-order model,Intra-particle diffusion model and Langmuir isothermal model could well describe the adsorption process of MB by LBC and LBC-N.According to the physicochemical properties and adsorption experiments of nitrogenous biochar,the adsorption process of LBC-N on MB molecules was mainly a result of π-π interaction,hydrogen bonding,electrostatic attraction and other chemical effects,and the synergistic effect of physical adsorption by pore filling.
lycium chinensis stalksnitrogen-doped biocharureaadsorptionmethylene blue
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