裸和Polymer包覆氧化铁超顺磁性纳米粒子对U（VI）的去除
Bare and Polymer Coated Iron Oxide Superparamagnetic Nanoparticles for Effective Removal of U (VI) from Acidic and Neutral Aqueous Medium
摘要：
在水中合成了超顺磁性γ-Fe_2O_3纳米粒子（直径为5 nm）。裸颗粒在~ pH 2时表现出良好的胶体稳定性，这是因为具有+25 mV的表面电荷的强静电排斥。聚丙烯酸（PAA）包覆的颗粒在~ pH 7下表现出显著的胶体稳定性，具有丰富的游离羧基作为后续官能化的反应位点。在这项工作中，我们使用zeta电位分析，透射电子显微镜，小角X-射线散射，电感耦合等离子体质谱法研究裸和涂层胶体超顺磁性纳米粒子在pH 2和pH 7的吸附行为的U（VI）。在pH = 2时，铀酰离子（UO_（22+））吸附在裸颗粒表面，颗粒表面电荷减少。这引起颗粒附聚。在pH 7时，铀酰离子（UO 22+）水解并形成直径约50 nm的氢氧化铀板状颗粒。PAA包覆的氧化铁纳米颗粒吸附在这些氢氧化铀（VI）板的表面上以形成沉淀到分散体底部的大聚集体。在pH 2和pH 7下，通过外部磁场可以容易地从水环境中收集和提取所得到的U（VI）/纳米颗粒复合物。结果表明，无论是裸的还是聚合物包覆的超顺磁性γ-Fe 2 O3纳米粒子都是潜在的U（VI）吸附剂。
英文摘要：
Superparamagnetic γ-Fe2O3 nanoparticles (5 nm diameter) were synthesized in water. The bare particles exhibit good colloidal stability at ~ pH 2 because of the strong electrostatic repulsion with a surface charge of +25 mV. The polyacrylic acid (PAA)-coated particles exhibit remarkable colloidal stability at ~ pH 7 with abundant free carboxyl groups as reactive sites for subsequent functionalization. In this work, we used zeta potential analysis, transmission electron microscopy, small angle X-ray scattering, and Inductively coupled plasma mass spectrometry to investigate the adsorption behavior of U (VI) on bare and coated colloidal superparamagnetic nanoparticles at pH 2 and pH 7. At pH 2, uranyl ion (UO22+) absorbed on the surface of the bare particles with decreasing particle surface charge. This induced particle agglomeration. At pH 7, uranyl ion (UO22+) hydrolyzed and formed plate-like particles of uranium hydroxide that were ~ 50 nm in diameter. The PAA-coated iron oxide nanoparticles absorbed on the surface of these U (VI) hydroxide plates to form large aggregates that precipitate to the bottom of the dispersion. At both pH 2 and pH 7, the resulting U (VI)/nanoparticle complex can be easily collected and extracted from the aqueous environment via an external magnetic field. The results show that both bare and polymer-coated superparamagnetic γ-Fe2O3 nanoparticles are potential absorbents for removing U (VI) from water.
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