Preparation Of Polymer Coated Magnetic Nanomaterials And Their Application For Adsorption And Separation

Magnetic nanomaterials have great advantages in remediation of contaminated actualwater for its low particle size, large surface area, and magnetic separation. In this article, weprepared two novel magnetic nanomaterials based on Fe3O4nanoparticles. Firstly, SiO2wascoated on Fe3O4nanoparticle, then thiol groups were modified on the Fe3O4@SiO2to formFe3O4@SiO2-SH. The second material was polydopamine coated Fe3O4. Then the preparedmagnetic materials were characterized with transmission electron microscope (TEM),Energy-dispersive spectroscope (EDS), and X-ray photoelectron spectroscopy (XPS), FourierTransform Infrared Reflectance Spectroscopy（FT-IR），Zeta potential instrument, andvibrating sample magnetometer（VSM）et al. Some pollutants were selected to investigate theadsorption property of the prepared materals.In the first part, the adsorption-desorption property of Fe3O4@SiO2-SH for mercuy ionwas studied. Effect of solution pH and coexist ions on mercury adsorption was investigated.Adsorption isothermal experiment indicated that the adsorption data fit the Langmuir model,and the maximum adsorption capacity calculated from Langmuir fitting was148.8mg/g at pH6.5. The adsorption kinetics study showed that adsorption data fit pseudo-second order kineticmodel well. The loaded mercury could be fully desorbed with1.0mol/L HCl containing3.0%of thiourea from sorbents. The adsorption capacity was still over90mg/g after five times ofrecycle, suggesting excellent reusability of the sorbents. The potential application ofFe3O4@SiO2-SH for removal of mercury from natural water was tested. The maximumadsorption capacity was over110mg/g in all tested water samples, showing excellentperformance in mercury adsorption from natural water. The Fe3O4@SiO2-SH was a promisingsorbent to treat mercury contaminated water effectively.In the second part, the adsorption and recovery of Fe3O4@SiO2-SH for trace gold fromsolution was investigated. Effect of solution pH and coexist ions on gold adsorption wasexamined. Adsorption isothermal experiment indicated that the adsorption data fit theLangmuir model, and the maximum adsorption capacity calculated from Langmuir fitting was84.75mg/g at pH5. The adsorption kinetics study showed that adsorption data fitpseudo-second order kinetic model well. The loaded mercury could be fully desorbed with1mol/L HCl containing2.0%of thiourea from sorbents. The adsorption capacity was around50 mg/g after five times of recycle, suggesting excellent reusability of the sorbents.In the third part, the dopamine polymerized spontaneously under room temperature toencapsulate the Fe3O4nanopartilces to form Fe3O4/PDA hybrid material. To investigate theadsorption ability of Fe3O4/PDA, heavy metal ions and dyes were selected as target pollutants.The adsorption of pollutants was pH dependent due to the variation of surface charges atdifferent solution pH. The removal efficiencies of cation pollutants enhanced with solution pHincreasing, and that of anion pollutant was just the opposite. Under the optimal solution pH,the maximum adsorption capacity calculated from Langmuir adsorption isotherm formethylene blue, tartrazine, Cu(Ⅱ), Ag(Ⅰ), and Hg(Ⅱ) were204.1,100.0,112.9,259.1, and467.3mg/g, respectively. The adsorption kinetics study showed that adsorption of all thepollutants fit pseudo-second order kinetic model well. Methylene blue, Cu(Ⅱ), andHg(Ⅱ)were desorbed with0.010mol/L HCl solution, and0.010mol/L HNO3solution wasused to desorb Ag(Ⅰ), while tartrazine was desorbed with0.010mol/L NaOH solution. Theregenerated sorbent was used in the next adsorption process. The sorbent still remained goodadsorption efficiency after three cycles. The adsorption capacities of methylene blue,tartrazine, Cu(Ⅱ), and Hg(Ⅱ) showed a little decrease except that of Ag(Ⅰ). TheFe3O4/PDA polymer exhibited high adsorption capacity for multiple pollutants and goodreusability.