Adsorption of Ce modified metal organic framework to fluorine
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摘要: 利用水热合成法,将金属Ce与合成金属有机骨架材料(MOFs)所需的反应前体混合,通过“一锅法”和“两步法”分别合成性能不同的Ce/MOF-5材料。采用SEM、XRD、BET等对合成材料进行表征。结果表明:不同的方法合成的Ce/MOF-5形貌有较大差异,对氟吸附性能也不同。并测定了初始浓度、pH值、吸附时间对F−吸附效果的影响。实验表明,通过“一锅法”合成的Ce/MOF-5材料对F−的吸附在pH=7、吸附时间为60 min左右即可达到吸附平衡,吸附量为109.6 mg·g−1,符合准二级动力学模型和Freundlich等温吸附模型。Abstract: The Ce/MOF-5 materials with different properties were synthesized by means of hydrothermal synthesis method by mixing Ce with the reaction precursors required for the synthesis of metal organic framework materials (MOFs). The synthetic materials were characterized by SEM, XRD and BET, etc. The results show that the Ce/MOF-5 synthesized by different methods shows significant differences in morphology and fluorine adsorption performance. The effect of the initial concentration, pH value and adsorption time on the adsorption effect of F− was also determined. The experiments show that the adsorption of F− by Ce/MOF-5 material synthesized by the "one-pot method" obtains an adsorption balance of 109.6 mg·g−1 at pH=7, with a adsorption time of about 60 min. It conforms to the quasi-second order kinetic model and Freundlich isothermal adsorption model.
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Key words:
- fluoride /
- adsorption /
- MOF-5 /
- one-pot synthesis /
- adsorption thermodynamics /
- adsorption kinetics
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表 1 Ce/MOF-5对F−的吸附等温线拟合参数
Table 1. Adsorption isotherm fitting parameters of Ce/MOF-5 to F−
Langmuir model Freundlich model qm KL R2 n KF R2 Ce/MOF-5Ⅰ 158.22 0.074 0.984 1.859 16.75 0.994 Ce/MOF-5Ⅱ 136.43 0.034 0.977 1.358 6.68 0.967 Notes:qm—Saturated adsorption capacity(mg·g−1); KL—Adsorption correlation constant(L·mg−1); KF, n—Adsorption correlation constants. 表 2 Ce/MOF-5对F-的吸附动力学拟合参数
Table 2. Adsorption kinetics fitting parameters of Ce/MOF-5 for F-
Quasi-first-order Quasi-second-order Elovich equation Qc K1 R2 Qc K2 R2 α β R2 Ce/MOF-5Ⅰ 79.42 0.064 0.933 110 0.01 0.999 526.02 0.0885 0.991 Ce/MOF-5Ⅱ 68.44 0.053 0.895 66.7 0.02 0.973 182.79 0.1044 0.950 Note: Qc—Theoretical calculated adsorption amount(mg·g−1); α, β—Elovich constants, which represent the initial adsorption rate g/(mg·min) and desorption constant (g·mg-1); K1—Pseudo first-order adsorption rate constant (min-1); K2—Pseudo second-order adsorption rate constant g/(mg·min). 表 3 Ce/MOF-5对F-的吸附和脱附效率
Table 3. Adsorption and desorption efficiency of Ce/MOF-5 for F-
Recycling 1 Recycling 2 Recycling 3 Adsorption rate of Ce/MOF-5 Ⅰ/% 98 95 93 Desorption rate of Ce/MOF-5 Ⅰ/% 96 92 89 Adsorption rate of Ce/MOF-5 Ⅱ/% 97 93 90 Desorption rate of Ce/MOF-5 Ⅱ/% 95 91 87 表 4 不同吸附剂对F-吸附性能的比较
Table 4. Comparison of F- adsorption properties by different adsorbents
Material MOF-5 Ce/MOF-5Ⅰ MIL-53(Fe) ZIF-8 ZIF-9 UIO-66(Zr) Cu-MOF[5] Adsorption capacity 0 109.6 16.96 0.90 1.70 40.09 0.2 -
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