氧化石墨烯的表面酸碱性质及其对U（Ⅵ）和Th（Ⅳ）的吸附研究
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摘要
氧化石墨烯(GO)是一种新型碳纳米材料,具有独特的物化性质及广泛的应用前景。GO表面有大量的含氧基团,可强烈吸附重金属离子,有望应用于放射性废水处理。因此,研究氧化石墨烯的表面酸碱性质及其对放射性核素的吸附作用具有重要意义。
采用Hummers法制备了氧化石墨并通过超声波处理得到了GO；用氢氧化钠溶液纯化了GO,同时分离并纯化了氧化碎片(CFs)；采用FT-IR、拉曼光谱、XRD、TEM和XPS等手段对CFs以及除去CFs前(ASGO)、后(BWGO)的氧化石墨烯进行了详细表征；用连续电位滴定法研究了BWGO的表面酸碱性质。结果表明,CFs对GO在水溶液中的分散性、表面电荷密度、导电性以及对重金属离子的吸附等均具有显著影响,去除CFs非常必要。解吸动力学研究表明,在氢氧化钠溶液中,CFs的解吸是一个相对缓慢的动力学过程。氧化程度不同的BWGO均含-COOH、-OH、C=C和六元环等官能团,但随着氧化程度的增大,其比表面积和含氧官能团数量逐渐增加。
采用批式法分别研究了U(Ⅵ)和Th(Ⅳ)在不同氧化程度的BWGO上的吸附行为。结果表明,随着氧化程度的增加,BWGO对U(Ⅵ)和Th(Ⅳ)的吸附能力显著增强；离子强度对吸附的影响较弱；U(Ⅵ)和Th(Ⅳ)可能主要以表面配合反应被吸附；Langmuir模型可以解释U(Ⅵ)和Th(Ⅳ)的吸附等温线,拟合得到的最大吸附量为10-4-10-3mol/g,表明GO是一种U(Ⅵ)和Th(Ⅳ)的优秀吸附材料。
As a new carbon nanomaterial, graphene oxide (GO) has unique physicochemical properties and extensive application prospects. GO contains a large number of surface functional groups that strongly promote the adsorption of heavy metal ions, may be applied in liquid radioactive waste treatment. Therefore, it's of significance to study the acid-base chemistry and the adsorption of radionuclides on graphene oxide.
Graphite oxide was prepared from purified natural graphite by Hummers method. GO was obtained by ultrasonic treatment of the graphite oxide, and purified with sodium hydroxide solution, meanwhile oxidation debris (carbonaceous fragments, CFs) was isolated and purified. CFs, GO before (ASGO) and after (BWGO) removal of CFs were characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. The acid-base chemistry of BWGO was studied by continuous potentiometric titrations. It was found that CFs significantly influence the dispersibility, surface charge density, adsorption of heavy metals on GO and electrical conductivity of graphene produced from reduction of GO, therefore it's necessary to remove CFs from GO. The desorption kinetics of CFs in NaOH solution was relatively slow. Although BWGOs at different oxidation levels contain the same groups, such as-COOH,-OH, C=C and hexatomic ring, the oxygen-containing functional groups and specific surface area increase with increasing oxidation level.
The adsorption of U(Ⅵ) and Th(Ⅳ) on BWGO at different oxidation levels were carried out by batch experiments. It was found that with the increase of oxidation degree, the adsorption capacities of U(Ⅵ) and Th(Ⅳ) are significantly enhanced. Ionic strength has a weak effect on the adsorption, indicating that the adsorption of U(Ⅵ) and Th(Ⅳ) is mainly via surface complexation reactions. The adsorption isotherms of U(Ⅵ) and Th(Ⅳ)can be interpreted by Langmuir model, which give a maximum adsorption capacity range in104-10"3mol/g, suggesting that GO is an excellent adsorbate for U(Ⅵ) and Th(Ⅳ).
采用Hummers法制备了氧化石墨并通过超声波处理得到了GO；用氢氧化钠溶液纯化了GO,同时分离并纯化了氧化碎片(CFs)；采用FT-IR、拉曼光谱、XRD、TEM和XPS等手段对CFs以及除去CFs前(ASGO)、后(BWGO)的氧化石墨烯进行了详细表征；用连续电位滴定法研究了BWGO的表面酸碱性质。结果表明,CFs对GO在水溶液中的分散性、表面电荷密度、导电性以及对重金属离子的吸附等均具有显著影响,去除CFs非常必要。解吸动力学研究表明,在氢氧化钠溶液中,CFs的解吸是一个相对缓慢的动力学过程。氧化程度不同的BWGO均含-COOH、-OH、C=C和六元环等官能团,但随着氧化程度的增大,其比表面积和含氧官能团数量逐渐增加。
采用批式法分别研究了U(Ⅵ)和Th(Ⅳ)在不同氧化程度的BWGO上的吸附行为。结果表明,随着氧化程度的增加,BWGO对U(Ⅵ)和Th(Ⅳ)的吸附能力显著增强；离子强度对吸附的影响较弱；U(Ⅵ)和Th(Ⅳ)可能主要以表面配合反应被吸附；Langmuir模型可以解释U(Ⅵ)和Th(Ⅳ)的吸附等温线,拟合得到的最大吸附量为10-4-10-3mol/g,表明GO是一种U(Ⅵ)和Th(Ⅳ)的优秀吸附材料。
As a new carbon nanomaterial, graphene oxide (GO) has unique physicochemical properties and extensive application prospects. GO contains a large number of surface functional groups that strongly promote the adsorption of heavy metal ions, may be applied in liquid radioactive waste treatment. Therefore, it's of significance to study the acid-base chemistry and the adsorption of radionuclides on graphene oxide.
Graphite oxide was prepared from purified natural graphite by Hummers method. GO was obtained by ultrasonic treatment of the graphite oxide, and purified with sodium hydroxide solution, meanwhile oxidation debris (carbonaceous fragments, CFs) was isolated and purified. CFs, GO before (ASGO) and after (BWGO) removal of CFs were characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. The acid-base chemistry of BWGO was studied by continuous potentiometric titrations. It was found that CFs significantly influence the dispersibility, surface charge density, adsorption of heavy metals on GO and electrical conductivity of graphene produced from reduction of GO, therefore it's necessary to remove CFs from GO. The desorption kinetics of CFs in NaOH solution was relatively slow. Although BWGOs at different oxidation levels contain the same groups, such as-COOH,-OH, C=C and hexatomic ring, the oxygen-containing functional groups and specific surface area increase with increasing oxidation level.
The adsorption of U(Ⅵ) and Th(Ⅳ) on BWGO at different oxidation levels were carried out by batch experiments. It was found that with the increase of oxidation degree, the adsorption capacities of U(Ⅵ) and Th(Ⅳ) are significantly enhanced. Ionic strength has a weak effect on the adsorption, indicating that the adsorption of U(Ⅵ) and Th(Ⅳ) is mainly via surface complexation reactions. The adsorption isotherms of U(Ⅵ) and Th(Ⅳ)can be interpreted by Langmuir model, which give a maximum adsorption capacity range in104-10"3mol/g, suggesting that GO is an excellent adsorbate for U(Ⅵ) and Th(Ⅳ).
引文
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