The Study On Functionalized Magnetic Core/Shell Structured Fe₃O₄@SiO₂ Nano-particles Adsorbents And Properties Of Removing Contaminants From Water

Based on the ideas of pollutant removal and resources recycling from water,the study synthesized the types of magnetic core/shell structured nano-particles adsorbents for removal of phosphate and antibiotics.Basically,the study synthesized magnetite nano-particles with regular shape and approximately uniform diameters through chemical precipitation methods and coated SiO₂ and further hydrous metal oxides on the surfaces producing Fe-Si-La and Fe-Si-Al for phosphate removal.The well magnetite crystalline types was well defined through XRD images.The TEM images clearly shows Fe-Si-La and Fe-Si-Al with well core/shell structures including magnetite which provides adsorbents with magnetic properties as the‘core'and hydrous metal oxides which provides adsorbents with adsorption site as the‘shell'.The saturated magnetization of Fe-Si-La and Fe-Si-Al is 51.27emu/g and 56.00emu/g,respectively,which assures successful magnetic separation of solid and liquid;the specific surface area of Fe-Si-La and Fe-Si-Al is 47.73m²/g and 47.21m²/g.Furthermore,to assess the phosphate removal properties of Fe-Si-La and Fe-Si-Al,the study emphasized on various environmental effects that influenced phosphate removal efficiency of Fe-Si-La and Fe-Si-Al,respectively.The adsorption isotherms of Fe-Si-La and Fe-Si-Al are both better fitted by Langmuir model than Freundlich model,and the maximum adsorption capacity of Fe-Si-La and Fe-Si-Al are 27.78mgP/g?R²=0.995?and 12.90mgP/g?R²=0.995?,respectively.Fe-Si-La and Fe-Si-Al are both able to remove phosphate rapidly and with high efficiency,and adsorption kinetics can be described well by pseudo-second-order model?R²=0.999?.The phosphate removal efficiency of Fe-Si-La and Fe-Si-Al are affected by pH condition significantly,and the phosphate removal rate increased and then decreased with the changes of pH from 2 to 12.The optimum adsorption condition of phosphate on Fe-Si-La and Fe-Si-Al are 5-9 and 5-12,respectively.In acidic condition the phosphate removal rate was prohibited by dissolution of hydrous metal oxides on surface of adsorbents,while in base condition the phosphate removal rate was decreased by prohibition of complexation reaction and competitiveness effects of hydroxyl.With different coexisting ions,the order of negative effects on Fe-Si-La and Fe-Si-Al was humic acid>bicarbonate?sulfate>nitrate?chloride and bicarbonate>humic>sulfate>nitrate?chloride,respectively.The changes of ionic strength from 0.001mol/L to1mol/L has no obvious effect on phosphate removal rateof Fe-Si-La and Fe-Si-Al.In treatment of domestic sewage,the optimum dosage of Fe-Si-La and Fe-Si-Al is 0.2kg/ton and 1.25kg/ton.The desorbed adsorbents can be regenerated by HCl,and Fe-Si-La and Fe-Si-Al both keep high and stable adsorption rate and desorption rate in five rounds of adsorption-desorption-regeneration experiments.Finally,the study explore the properties of magnetite-based adsorbents for antibiotics removal by synthesizing two magnetic nano-particles Fe-A-Ag and Fe-A-Al through coating and grafting.The maximum adsorption rate of oxytetracycline on Fe-A-Ag amd Fe-A-Al was 191.20mg/g and 32.66mg/g,respectively,which is 33.66 times and4.91 times as high as the capacity of adsorbents without metal ion grafting.In investigation of adsorption kinetics,The Fe-A-Al and Fe-A-Ag are able to removal 35%and 31%of tetracycline when initial concentration of oxytetracycline is 5mg/L and 50mg/L within 1 hour and8hours,respectively.The antibiotics can be significantly removed and recycled by magnetic nano-particles synthesized.