Preparation Of Fe₃O₄@MoS₂-Biochar And Study On Its Adsorption Performance For Eu（Ⅲ） In Solution

Nowadays,the increasing radionuclides will be released into the aquatic environments as a result of the development of long-term operation of nuclear energy and nuclear fuel cycle facilities.even at low concentration and must be removed from the affected water systems due to their toxicity and radioactivity.The preparation method of biochar is simple,the source of raw materials is wide,and it has a well-developed pore structure,huge specific surface area,more surface compounds and good mechanical strength.It has become one of the commonly used adsorbents for adsorbing heavy metals and radioactive elements.Due to the small particle size and huge specific surface area,magnetic nanomaterials have unique surface effects,and also have good magnetic response characteristics,easy to separate,reproducible and recyclable,and play a positive role in the adsorption of heavy metals that are difficult to handle by traditional processes.However,the material also has limitations such as easy agglomeration,easy passivation,and poor chemical stability.Loading on biochar will overcome these shortcomings of magnetic nanomaterials.In this paper,using corn stalks and peanut shells as raw materials,biochar was prepared by hydrothermal method,and Fe₃O₄@Mo S₂with core-shell structure was loaded on the biochar to successfully prepare Fe₃O₄@Mo S₂-biochar.The morphology was characterized by scanning electron microscope（SEM）.Fourier transform infrared spectroscopy（FT-IR）was used to analyze surface functional groups,and X-ray diffraction analysis（XRD）was used to analyze the phase structure of the material.BET analyzer and porosity tester were used to measure specific surface area and micropore structure.The effects of different p H values,solid-liquid ratio,temperature,adsorption time,ions in the solution on the adsorption effect,as well as the adsorption kinetics and adsorption isotherms of Eu（Ⅲ）by modified biochar were studied.The main conclusions are as follows:（1）Both corn stalks（PBC）and peanut shells（PBC）showed a slightly smooth surface,mostly sheet-like structures,and some of them showed fractured pore structures.A large number of spherical fine particles with rough surface can be clearly observed on the surface of the two modified biochars.This is the Fe₃O₄@Mo S₂-biochar composite material after in-situ growth of Mo S₂on the smooth spherical particles of Fe₃O₄.The characteristic peaks of the infrared spectra of corn stalks and peanut shells are basically the same,indicating that both types of biochar have abundant functional groups,and Fe₃O₄@Mo S₂-biochar has a strong carboxylate symmetric stretching vibration peak.After the biochar is modified by Fe₃O₄@Mo S₂,the peak intensity of the C=O stretching vibration peak is significantly reduced,the above functional groups improve the adsorption performance of Fe₃O₄@Mo S₂-biochar for Eu（Ⅲ）through chemical reactions such as complexation reaction and ion exchange.After surface modification with Fe₃O₄@Mo S₂,the micropore area of biochar is reduced,and the number of micropores is also reduced to a certain extent.The possible reason is that a small part of Fe₃O₄@Mo S₂has blocked the micropores of biochar structure.But most of the core-shell structure of Fe₃O₄@Mo S₂is compounded on the surface of biochar,increases the specific surface area of the composite material,which leads to more contact sites.T（2）The adsorption of Eu（Ⅲ）on PBC and Fe₃O₄@Mo S₂-PBC was studied by batch experiment.With the increase of the dosage,the removal rate of Eu（Ⅲ）by PBC and Fe₃O₄@Mo S₂-PBC gradually increases;the adsorption is not greatly affected by the ionic strength,but strongly depends on the change of p H,which shows that the surface complexation or ion exchange helps PBC and Fe₃O₄@Mo S₂-PBC to adsorb Eu（Ⅲ）.The adsorption of Eu（Ⅲ）by PBC reached equilibrium within 6 h,while the adsorption equilibrium time of Fe₃O₄@Mo S₂-PBC was 2 h.The entire process of Eu（III）adsorption by the two biochars can be better described by the pseudo-second-order kinetic equation,and the adsorption isotherm is more in line with the Langmuir adsorption isotherm model,this shows that the adsorption process of Eu（Ⅲ）on the two kinds of biochar is dominated by chemical adsorption,and the adsorption is monolayer adsorption.At p H=6 and temperature of 318K,the dosage of PBC is 0.1 g,and the dosage of Fe₃O₄@Mo S₂-PBC is 0.05 g,the maximum adsorption capacity for Eu（Ⅲ）is 20.32 mg g^-1,37.13 mg g^-1,respectively.（3）The adsorption of Eu（Ⅲ）on CBC and Fe₃O₄@Mo S₂-CBC was studied by batch experiment.The removal rate of Eu（Ⅲ）by CBC and Fe₃O₄@Mo S₂-CBC increases gradually with the increase of the dosage.The adsorption depends on the change of p H value,but it is not greatly affected by the ionic strength,indicating that the adsorption reaction is mainly ions.The exchange and the outer surface are complexed there.The adsorption amount of Eu（Ⅲ）by CBC and Fe₃O₄@Mo S₂-CBC gradually increased with time.Both the Eu（Ⅲ）adsorption process can be better described by the pseudo-second-order kinetic equation,and the adsorption isotherm is more in line with the Langmuir adsorption isotherm model,this shows that the adsorption process of Eu（Ⅲ）by the two kinds of biochar is dominated by chemical adsorption,and the adsorption belongs to monolayer adsorption.At p H=6 and temperature of 318K,the dosage of CBC is 0.1 g,and the dosage of Fe₃O₄@Mo S₂-CBC is 0.05 g,the maximum adsorption capacity for Eu（Ⅲ）is 18.27mg g^-1and 34.09 mg g^-1,respectively.