Study On Adsorption And Remediation Of Uranium In Water By Carbon Loaded Nano-Zero-Valent Iron

Uranium has radioactive and heavy metal toxicity,which will cause serious harm to the ecological environment and human health.Biochar has a large surface area,abundant surface functional groups and a dense microporous structure.The adsorption property of this special surface structure is used as an environmental adsorbent for the adsorption of various pollutants in environmental remediation,but its scope of application and adsorption capacity are limited.Nanometer zero-valent iron particles with small surface area and strong reducibility play an important role in environmental remediation.But it is unstable,easy to oxidize and agglomerate,which leads to the decrease of reaction activity,the difficulty of separation and recovery after reaction,and the low reuse rate.Loading nanometers through biochar zero-valent iron,giving full play to the advantages of both,making it a green and environmentally friendly adsorbent.On the basis of previous studies,three materials,biochar,nano-zero-valent iron and biochar-loaded nano-zero-valent iron,were prepared and used to compare the adsorption of uranium in solution environment.The effects of the best adsorption material and the main related experimental variables on the adsorption process were obtained.The results are as follows:(1)Preparation of biochar(BC)using agricultural waste raw material rice husk,synthesis of nano-zero-valent iron(n ZVI)and biochar-loaded nano-zero-valent iron(n ZVI/BC)by liquid phase reduction.Characterization by X ray diffraction(XRD),Scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR).It was found that nano-zero-valent iron particles were not agglomerated and uniformly dispersed on biochar,indicating successful loading.(2)Through kinetic experiments and isothermal adsorption model analysis,it is found that the adsorption process of biochar on uranium is more in line with Freundlich model and Quasi-second-order kinetic model;the adsorption process of nano-zero-valent iron on uranium is more in line with Langmuir model and Quasi-second-order kinetic model;the adsorption process of biochar-loaded nano-zero-valent iron to uranium is more in line with Langmuir model and Quasi-second-order kinetic model.Indicating that the adsorption process of uranium by biochar is surface inhomogeneous adsorption,while the adsorption of uranium bynano zero-valent iron and biochar-loaded nano zero-valent iron is mainly monolayer adsorption.(3)Three materials were used to study the adsorption of uranium in aqueous solution to obtain the best adsorption conditions.The results showed that the adsorption of biochar was the best under the conditions of 0.018 g,p H=5 and 180 min,and the adsorption capacity was 10.53 mg/L,the adsorption rate was 47.38%;the adsorption of nano-zero-valent iron was the best under the conditions of 0.025 g,p H=3 and 60 min,the adsorption capacity was 15.96 mg/g,the adsorption rate was99.76%,while the adsorption rate of biochar-loaded nano-zero-valent iron was 96%and the adsorption capacity was 19.2 mg/L,under the conditions of 0.01 g,p H=5 and2 h reaction time.By comparison of adsorption experiments,it is found that n ZVI/BC can better remove uranium in polluted water under the best adsorption conditions.At the same time,the study found that the best conditions needed by n ZVI/BC are easier to meet,so the remediation of uranium contaminated water is feasible.