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近年来,随着冶金、光伏、锂电池等工业产业的不断发展,产生了大量的含氟废水(检出浓度从几十到上千mg·L−1不等),水体氟污染问题对自然环境以及人体健康都构成了严重威胁[1]。因此,亟须探求一种成本低廉、处理高效、易于操作的除氟技术。目前,去除水体中氟离子的主要方法有沉淀法[2]、离子交换法[3]、膜处理法与吸附法[4]。沉淀法适合高氟水体的预处理过程,并且会改变出水水质;离子交换法、电化学法所需的成本较高、操作复杂;膜处理法因受半透膜的影响效果不稳定、花费较高并且严重浪费水资源,应用范围不广。目前,吸附法因其经济、灵活、操作简单的优点被大量应用于去除氟的研究中[5]。
近年来国内外开发了众多吸附材料并应用于含氟废水处理,主要包含活性氧化铝[6]、粘土材料[7]、活性炭[8]、生物炭[9]、金属有机框架材料[10]等。金属有机框架材料(metal-organic frameworks, MOFs)是一种新型的多孔配位聚合物,由无机金属离子或团簇与有机配体自组装连接而成[11]。MOFs 具有较大的比表面积且制备方法较简单,目前已广泛用于吸附、催化、检测等领域[12-13]。赵瑨云等[14]采用水热合成法制备了一种毛线团状结构的La-MOFs,其对氟的吸附容量可达43.1 mg·g−1。JEYASEELAN等[15]合成了Ce@BDC和Ce@ABDC并用于除氟,结果表明,Ce@BDC和Ce@ABDC对氟的最大吸附容量分别为4.88 mg·g−1和4.91 mg·g−1。HE等[16]以类似的方式合成了Ce(Ⅲ)-BDC,发现Ce(Ⅲ)-BDC对氟的最大吸附容量为128.0 mg·g−1。本团队[17]对比了有机配体(对苯二甲酸(BDC)、邻苯二甲酸、间苯二甲酸)对Ce基MOFs除氟性能影响,发现对苯二甲酸(BDC)为配体形成的Ce-BDC的吸附容量最大(139.5 mg·g−1)。WANG等[18]将NH2-MIL-53(Al)衍生的介孔碳应用于去除水溶液中Cr(Ⅵ)和甲基橙,相比前体,发现衍生碳对污染物的吸附容量有较大提升且材料自身更加稳定。目前,MOFs衍生碳已经被大量研究并应用,但将其应用于除氟领域的研究还较少。
本研究首先以溶剂热法制备得到Ce-BDC,再以此为前驱体,在空气和氮气的气流中热解,得到Ce-BDC-400(A)和Ce-BDC-400(N)。利用多种表征技术分析其结构,结合吸附等温线、吸附动力学和吸附热力学等手段,讨论了这2种衍生碳对氟的吸附性能;此外,考察了共存阴离子、溶液初始 pH 对氟吸附过程的影响;最后将所制得的吸附材料应用于实际含氟废水的处理,分析了Ce-MOFs衍生碳在实际水体中的除氟性能。
Ce-BDC衍生碳的除氟性能与机理
Removal performance and mechanism of fluoride by Ce-BDC-derived carbon
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摘要: 以Ce-BDC为原料,在空气和N2的氛围中煅烧形成的衍生碳Ce-BDC-400(A)和Ce-BDC-400(N)。使用X射线粉末衍射仪、扫描电子显微镜等表征手段 对其微观形貌结构、元素组成、官能团特征、晶型结构分别进行了表征和分析,并通过吸附拟合实验考察了Ce-BDC-400(A)和Ce-BDC-400(N)对水中氟离子的去除性能及可能的机制。结果表明成功制备了2种衍生碳。Ce-BDC-400(A)和Ce-BDC-400(N)对氟离子的吸附动力学符合准二级动力学模型,吸附等温线符合 Langmuir等温线模型。Ce-BDC-400(A)和Ce-BDC-400(N)对氟离子的吸附是自发进行的,且对氟的吸附过程是放热反应。Ce-BDC-400(A)和Ce-BDC-400(N) 对氟离子的最大吸附容量分别为140.6 mg·g−1和155.1 mg·g−1。Ce-BDC-400(A)和Ce-BDC-400(N)在宽 pH (3~10)范围内具有优良而稳定的除氟性能,并在实际水体处理中显示出优异的除氟性能。
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关键词:
- 铈基金属有机框架材料 /
- 衍生碳 /
- 除氟 /
- 吸附 /
- 水处理
Abstract: The derivatives Ce-BDC-400(A) and Ce-BDC-400(N) were formed by calcination of Ce-BDC in an atmosphere of air and N2. XRD and SEM was used to characterize the microstructure, elemental composition, functional group characteristics, and crystal structure of the two materials. The removal performance and mechanism of fluoride by Ce-BDC derived carbon: Ce-BDC-400(A) and Ce-BDC-400(N), were investigated through absorption fitting experiments. The results showed that the successful synthesis of adsorption materials occurred. The adsorption kinetics of Ce-BDC-400(A) and Ce-BDC-400(N) to fluoride ion conformed to the quasi-second order kinetic model, and the adsorption isotherm conformed to the Langmuir model. The adsorption of fluoride by Ce-BDC-400(A) and Ce-BDC-400(N) was spontaneous and exothermic. The maximum adsorption capacities of Ce-BDC-400(A) and Ce-BDC-400(N) to fluoride were 140.6 and 155.1 mg·g−1, respectively. Ce-BDC-400(A) and Ce-BDC-400(N) presented an excellent and stable fluoride removal performance over a wide pH range (3-10), and an excellent fluoride adsorption performance in actual water treatment.-
Key words:
- cerium based metal–organic framework /
- derived carbon /
- fluoride removal /
- adsorption /
- water treatment
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表 1 Ce-BDC-400(A)和Ce-BDC-400(N)的孔结构参数
Table 1. Textural parameters of Ce-BDC-400(A) and Ce-BDC-400(N)
样品 比表面积/(m2·g−1) 平均孔径/nm 总孔容/(cm3·g−1) Ce- BDC-400 (A) 36.06 18.22 0.164 Ce- BDC-400 (N) 31.09 3.97 0.031 -
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