【作者】 李平；

【导师】 陶霞；

【作者基本信息】 北京化工大学 ， 化学工程与技术， 2013， 硕士

【摘要】 六价铬Cr(Ⅵ)具有高毒性并且极易溶于水。一旦富含Cr(Ⅵ)的废水进入自然水体中,将对动植物甚至人类健康产生极大的威胁。鉴于六价铬Cr(Ⅵ)的高毒性以及高水溶性,必须在废水排入水体和土壤之前将其去除。处理六价铬最常用方法有化学还原／沉淀、离子交换、膜分离、吸附等,其中吸附脱除是一种操作简单、经济有效的方法。目前Cr(Ⅵ)的吸附脱除的研究主要集中在对高效的新型吸附的开发和研究上。石墨烯是一种由碳原子以sp2杂化轨道构成,呈蜂巢结构的六边型晶格平面薄膜,是一种只有单个碳原子厚度的新型二维材料。已经展现出其在水污染处理的应用前景。本课题通过引入聚二烯丙基二甲基氯化铵(PDDA)到石墨烯(RGO)表面,改善RGO的水溶性；接着用水热法将磁性CoFe2O4纳米颗粒分散到RGO片层上,赋予该材料磁性分离功能,进而首次成功制备了双功能化的RGO-PDDA-CoFe2O4复合材料用于六价铬Cr(Ⅵ)的吸附脱除。本文所制备RGO-PDDA-CoFe2O4复合材料保持了石墨烯的二维(2D)片层结构,PDDA的功能化和CoFe2O4纳米颗粒与RGO的复合没有破坏RGO的2D结构；PDDA和CoFe2O4的引入没有带进其他的杂质；CoFe2O4纳米颗粒是以六方尖斜晶的晶体形式分散在RGO表面,实现CoFe2O4的磁性功能化。该材料对Cr(Ⅵ)的饱和吸附量达到265.5mg/g,相比RGO-CoFe2O4,吸附量提高了24.8%；同时也高于其他文献报道的一些纳米材料对Cr(Ⅵ)的吸附量。另外,吸附到材料上的Cr(Ⅵ)有69.7%被还原为毒性和水溶性更小的Cr (Ⅲ);RGO-PDDA-CoFe2O4在酸性条件下对Cr(Ⅵ)吸附量明显高于碱性条件下的吸附量,对Cr(Ⅵ)吸附的最佳pH值为2；升高吸附系统的温度有利于RGO-PDDA-CoFe2O4对Cr(Ⅵ)的吸附；Cr(Ⅵ)的吸附机理包含了对Cr(Ⅵ)的吸附和还原。此外,动力学实验结果表明该材料对六价铬的吸附服从准二级吸附动力学特性。鉴于RGO-PDDA-CoFe2O4复合材料不仅可以有效的吸附Cr(Ⅵ),其具有磁性分离功能还使得该材料更有实际利用的价值,RGO-PDDA-CoFe2O4可以作为理想的Cr(Ⅵ)吸附剂,并且为进一步水处理提供了一种优秀的候选材料。更多还原

【Abstract】 Hexavalent chromium [Cr (Ⅵ)] is highly toxic and solutble, once entered the aquatic environment, Cr(Ⅵ) becomes a huge threat to humans, animals and plants due to its high toxicity and extreme solubility in aquatic system. Generally, Cr(Ⅵ) is treated via chemical reduction/precipitation, ion exchange, membrane separation and adsorption. Among these, adsorption is one of the most economical and technically feasible approaches. Recently, more researches focus on new adsorbents for the removal of Cr(Ⅵ)Graphene, is a one-atom-thick planar sheet of sp2-bonded carbon atoms that are densely packed in a honeycomb crystal lattice. It has been reported for wildly applications in wastewater remediation and this materials has shown promising potential. Dual-functionalized reduced graphene oxide (RGO) composites have been successfully synthesized by introducing poly(diallyldimethylammonium chloride)(PDDA) and magnetic CoFe2O4particles to the surface of RGO sheets via the reduction process of graphene oxide (GO) to RGO in the presence of PDDA, followed by the hydrothermal treatment of inorganic salts. Characterization results show that the as-prepared RGO-PDDA-CoFe2O4composites remain layered structure feature, and the CoFe2O4nanoparticles uniformly dispersed on the surface of RGO-PDDA sheets. Such RGO-PDDA-CoFe2O4composites exhibit excellent adsorption ability of Cr(VI) removal. The Cr(VI) removal capability reaches maximum up to265.5mg/g, which is24.8%higher than that of RGO-CoFe2O4and far larger than the previously reported values from other nanomaterials. Interestingly,69.7%of the up-taken Cr(VI) was reduced to less toxic and soluble Cr (III). The adsorption kinetics study reveals that the adsorption of Cr(VI) from aqueous solution over RGO-PDDA-CoFe2O4composites follows pseudo-second-order kinetic model. The dual-functionalized composites with the distinct advantages mentioned above serve as ideal candidates for aqueous environmental remediation.更多还原