Study On The Adsorption Performance Of Cd(Ⅱ) And As(Ⅴ) In Water By Surfactant-modified MnFe₂O₄ Composite Material

Industrial processes,especially smelting and processing of non-ferrous metals,produce a large number of wastewater containing cadmium,arsenic and other heavy metals,which seriously pollute terrestrial and aquatic ecosystems and cause great harm to human health.How to effectively remove cadmium,arsenic and other heavy metals from water bodies has attracted extensive attention from scholars at home and abroad.Among many cadmium and arsenic treatment technologies,adsorption is a simple and effective method for water treatment.Iron and manganese oxides have good adsorption properties.Iron oxides,manganese oxides and synthetic iron and manganese oxides have been widely used as adsorbents in the treatment of heavy metal ion wastewater.However,the modification of iron and manganese oxides with surfactants and their application in the removal of cadmium and arsenic are rarely reported.In this paper,CTAB/MnFe₂O₄/MnO₂composite materials modified by surfactants were prepared by co-precipitation method and analyzed by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,Fourier transform infrared spectroscopy（FIIR）and specific surface area（BET）The morphology and structure of the composites were characterized.The effects of pH,time,temperature,concentration of solution and organic acid on the adsorption performance of cadmium and arsenic were studied,and the adsorption mechanism was briefly analyzed.The main results are as follows:（1）The MnFe₂O₄/MnO₂ structure is improved by adding surfactant in the preparation process of MnFe₂O₄/MnO₂.A layer of reticular structure is added around the original spherical structure,and the specific surface area increases from 132.95 m²·g^-1 to 166.57m²·g^-1.In a wide pH range,both CTAB/MnFe₂O₄/MnO₂ and MnFe₂O₄/MnO₂ have strong adsorption capacity for Cd（II）,and the adsorption capacity of CTAB/MnFe₂O₄/MnO₂ is stronger than that of MnFe₂O₄/MnO₂.（2）The composite material CTAB/MnFe₂O₄/MnO₂ can effectively remove Cd（II）from simulated wastewater.The kinetic study shows that the whole adsorption process can reach equilibrium within 24 h,and the adsorption kinetic data are in accordance with the pseudo-second-order model.According to Langmuir isothermal model,the maximum adsorption capacity of CTAB/MnFe₂O₄/MnO₂ on Cd（II）at pH=6 is 89.85 mg·g-1.The effects of several common metal cations and organic compounds in water on Cd（II）adsorption were studied at pH=6.Ca²⁺,Mg²⁺and Na⁺all had a certain inhibitory effect on Cd（II）adsorption,and the order of inhibition was Ca²⁺>Mg²⁺>Na⁺.The addition of citric acid,tartaric acid and oxalic acid promoted the adsorption of Cd（II）.The order of influence was citric acid>tartaric acid>oxalic acid.（3）The adsorption behavior of As（V）on CTAB/MnFe₂O₄/MnO₂ follows the pseudo-second-order kinetic model and Langmuir isothermal model.After four cycles,CTAB/MnFe₂O₄/MnO₂ can still maintain more than 78%of As（V）removal rate,indicating that the CTAB/MnFe₂O₄/MnO₂ composite has good reusability.The adsorption of As（V）on CTAB/MnFe₂O₄/MnO₂ was inhibited by organic acids,and the inhibition was in the order of citric acid>tartaric acid>oxalic acid.In conclusion,the CTAB/MnFe₂O₄/MnO₂ composite prepared by the experiment has a large specific surface area,good adsorption performance for cationic Cd（II）and anionic As（V）,and is not easily affected by coexisting ions.It has a potential application prospect in the removal of Cd（II）and As（V）in aqueous solution.