| The development of industry(e.g.mining,electroplating,pesticides and fertilizers irrational)produced a large amount wastewater,has becoming an urgent environmental problem worldwide.Cd(II)is the main heavy metals in industry wastewater,and they are ranked among the most toxic heavy metals due to extremely biological toxicity.In order to reduce the pollutant emission,various methods such as chemical precipitation,electrochemical,membrane separation,ion exchange,electrolysis,and adsorption were applied to the removal of Cd(II)from wastewater.Among these methods,adsorption is the generally known with cost-effectively,simple and efficient.In this paper,surface imprinting method is used to prepare FS-ⅡP taking Cd(II)as a template,the paper studied the morphology,adsorption and regeneration repeatability of the polymer by combining with a series of characterization analysis,the main results are as follows:(1)Magnetic cadmium ion imprinted polymer(FS-IIP)were prepared using acid-resistant magnetic nanoparticles(FS)as precursor,cadmium ion as template,nitrobenzaldehyde as functional monomer,azobisisobutyronitrile as initiator,and ethylene glycol dimethacrylate as cross-linker by surface imprinting method.(2)Research on FS preparation process conditions shows:The magnetic iron nanoparticles(γ-Fe2O3)can be fully covered when absolute ethanol and isopropanol are used as solvents,the ratio of mass(γ-Fe2O3)to volume(3-aminopropyltriethoxysilane)is 1:2.(3)Characterization analysis results shows that:The main diffraction peak of FS-ⅡP coincides with the standard γ-Fe2O3 characteristic diffraction peak,proving that its main component is γ-Fe2O3 and the crystal form is good.The saturation magnetization is 21.14 emu/g,which achieves rapid separation under an external magnetic field and has good thermal stability.Various functional groups such as hydroxyl,amino and aldehyde groups form complexes with heavy metal ions through ion exchange,complexation,etc.,which improves the adsorption capacity of FS-ⅡP.(4)Research on the influencing factors on the adsorption of Cd(Ⅱ)by FS-ⅡP shows that:the equilibrium adsorption of Cd(Ⅱ)by FS-ⅡP reaches 50.59mg/g when the pH value is 6.0,the initial concentration of Cd(Ⅱ)is 80 mg/L,the reaction time is 10 min and the dosage is 0.15g.The adsorption process of Cd(Ⅱ)by FS-ⅡP is more suitable with the langmuir model and pseudo-second-order kinetic equation,indicating that the adsorption process is more inclined to the monolayer chemical adsorption on the adsorbent surface.After 5 adsorption-desorption cycles,the removal rate dropped from 97.34%to 72.24%,with good stability and reusability.(5)The adsorption experiment results of Pb(Ⅱ)in FS-IIP shows that:The equilibrium adsorption capacity is 15.59mg/g when the initial concentration of Pb(Ⅱ)is 50mg/L and the reaction time is 40min.The pseudo-second-order kinetic model is more suitable with the adsorption process of Pb(Ⅱ)by FS-ⅡP,indicating that the reaction is mainly the monolayer adsorption by chemical force.The adsorption experiment results of Zn(Ⅱ)in FS-IIP shows that:The equilibrium adsorption capacity is 15.59mg/g when the initial concentration of Zn(Ⅱ)is 60mg/L and the reaction time is 30min.The adsorption process of Zn(Ⅱ)by FS-IIP is more suitable with the pseudo-second-order kinetic model,which may include ion exchange and chelation,mainly chemical adsorption.(6)FS-ⅡP adsorption experiments on Cd(II),Pb(Ⅱ)and Cd(Ⅱ),Zn(Ⅱ)binary systems indicate that FS-IIP has adsorption selectivity for Cd(Ⅱ).In the binary system of Cd(Ⅱ)and Pb(Ⅱ),the selectivity coefficient of Cd(Ⅱ)in FS-IIP is 35.In the binary system of Cd(Ⅱ)and Zn(Ⅱ),the selectivity coefficient of Cd(Ⅱ)on FS-ⅡP is 14.3.(7)The results of adsorption experiments in the ternary system Pb(Ⅱ),Zn(Ⅱ)and Cd(Ⅱ)shows that:the partition coefficient of Cd(Ⅱ)by FS-ⅡP is 4.19,which is more than the coefficient of Pb(Ⅱ)and Zn(Ⅱ).It may be mainly due to the selectivity of FS-ⅡP for Cd(Ⅱ)in terms of coordination geometry. |
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