Characteristics Of Biochar Prepared From Giant Reed,Reed And Their Adsorption Properties Of Nitrobenzene In Aqueous Solution

Water pollution is a serious and widespread problem in rivers of China nowadays.In recent years,with the effective control and treatment of point source pollution such as industrial wastewater and urban domestic sewage,non-point source pollution has risen to become the main source of pollution in China's water environment.Among them,nitrobenzene is a common pollutant with high toxicity and great harm.In Beijing,giant reed and reed are common emergent plants on the banks of rivers which have a large amount of growth and an be taken locally.Biochar has the property of adsorbing pollutants and has strong functions.Therefore,this paper aims to prepare a series of biochar by pyrolyzing giant reed and reed at different temperatures and study their material structure differences,analyze the efficiency and dynamic process of nitrobenzene adsorption,in order to provide new biomass materials for river water pollution control.A series of biochar was prepared by pyrolyzing giant reed AArundo donax)and reed(Phragmites communis),the emergent plants growing in wetland,at temperatures ranging from 300? to 700?under nitrogen condition.The structures of biochar was characterized by thermogravimetric analysis(TG-DTG),elemental composition(C,H,N,O),Fourier transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM),and BET-NZ surface area analysis.The nitrobenzene was taken as adsorbed substance to investigate the adsorption properties of giant reed,reed derived biochar for organic pollutant in aqueous solution,and model the adsorption kinetic.The research results are as follows:1)With the increase of pyrolysis temperature,the surface functional groups of giant reed and reed derived biochar had changed,and the surface oxygen-containing functional groups,volatile aliphatic compounds and polar functional groups in the biochar were reduced gradually during the process of temperature increase.This process was accompanied by the dehydration of lignin and cellulose,and the formation of aromatic structures as well.2)With the increase of pyrolysis temperature,the surface structure of giant reed and reed biochar was more rough,the pore structure was more abundant,and the microporous structure began to appear.The surface areas of giant reed and reed biochar increased from 1.53m2/g(GR300)and 2.52 m2/g(R300)to 7.62 m2/g(GR700)and 8.91 m2/g(R700),respectively.3)The adsorption experiment showed that the adsorption amount of biochar increased with the increase of carbonization temperature,the reaction equilibrium times of giant reed biochar was about 4h,and that of reed biochar was 2h,and the final equilibrium adsorption ratios of giant reed and reed biochar were 99.9%(GR700)and 99.5%(R700),respectively.The excess adsorption amount of the adsorbents GR700 and R700 to nitrobenzene were 13.59 mg/g and 13.52 mg/g at 25?.Combining the yield of biochar with the amount of adsorption,the adsorption capacity of biochar pyrolyzed at low temperature was much larger than at high temperature.Therefore the adsorption efficiency of giant reed biochar prepared at 400? and reed biochar prepared at 300? were optimal.4)The research of adsorption kinetics showed that the adsorption process of giant reed derived biochar can be well described by pseudo-second-order kinetic model(R2=0.97),otherwise the adsorption dynamic of reed biochar followed pseudo-first-order kinetic mode(R2=0.98),which suggested that the adsorption process can be dominated by physical diffusion and chemical adsorption,respectively,and contains various adsorption processes.