ZIF材料对碘的吸附特性研究

doi:10.15541/jim20190351

摘要/Abstract

摘要：

核废水中的放射性碘对人类健康和环境有严重的危害, 但是由于碘在水中以多种形式存在, 很难准确测定其在水中的含量。开发能够准确测定水中碘单质含量的方法, 制备有效去除碘单质的材料对保护环境和人类健康尤其重要。为此, 本研究首先提出了用环己烷萃取法测定碘单质浓度的方法, 并且制备了两种沸石咪唑骨架材料ZIF-8和ZIF-67, 研究了ZIF-8和ZIF-67对水环境中碘的吸附行为。利用分析仪器对ZIF-8和ZIF-67材料进行了表征。结果表明: 两种材料都具有良好的化学结构和较大的比表面积。吸附动力学实验结果表明, 60 min内, 两种材料对碘的吸附可以达到平衡, 吸附行为更好地符合拟二级动力学模型。吸附热力学结果表明, 两种材料在水中对碘的吸附过程均为线性吸附。ZIF-8和ZIF-67材料对碘单质的吸附量可高达2000 mg·g ^-1。

关键词: ZIF-8, ZIF-67, 碘, 水溶液, 吸附

Abstract:

Radioactive iodine present in nuclear waste water streams is harmful to human health and environment. Since iodine will exist in multiple states in water, accurate quantification of the total iodine content in any given sample is very difficult. The development of a method for determining the total iodine content accurately in water, and finding materials which can effectively remove the iodine are of particular importance. Here, a method was proposed for determining the concentration of iodine by cyclohexane extraction. And two kinds of zeolite imidazole skeleton materials ZIF-8 and ZIF-67 were prepared to be used as adsorbents to effectively adsorb iodine from an aqueous environment. Samples ZIF-8 and ZIF-67 were characterized by different methods. The results show that these two kinds of materials have good chemical structure and large specific surface area. The results of adsorption kinetics experiments show that the adsorption of ZIF-8 and ZIF-67 materials to iodine can reach the equilibrium within 60 min. The iodine adsorption behaviors of both materials are fitted with the pseudo second-order kinetic model. Their adsorption thermodynamics indicate linear adsorption behavior for iodine in the case of both zeolites. Adsorption capacities of ZIF-8 and ZIF-67 for iodine could reach as high as 2000 mg·g ^-1.

Key words: ZIF-8, ZIF-67, iodine, aqueous solution, adsorption

中图分类号:

TQ174

刘蓉, 张炜, 陈元涛, 樊元睿, 胡广壮, 许成, 韩臻. ZIF材料对碘的吸附特性研究[J]. 无机材料学报, 2020, 35(3): 345-351.

LIU Rong, ZHANG Wei, CHEN Yuantao, FAN Yuanrui, HU Guangzhang, XU Cheng, HAN Zheng. Adsorption of Iodine by ZIF Materials[J]. Journal of Inorganic Materials, 2020, 35(3): 345-351.

图/表 11

图1 用环己烷从水中萃取碘后的碘-环己烷标准曲线

Fig. 1 Standard curve of iodine-cyclohexane after extraction of iodine from water with cyclohexane

图2 ZIF-8和ZIF-67的模拟及实验XRD图谱

Fig. 2 Simulated and experimental XRD patterns of ZIF-8 and ZIF-67

图3 ZIF-8及ZIF-67吸附碘前后扫描电镜照片

Fig. 3 SEM images of ZIF-8 and ZIF-67 before and after iodine adsorption (a) ZIF-8 before adsorption, (b) ZIF-8 after adsorption, (c) ZIF-67 before adsorption, (d) ZIF-67 after adsorption

图4 ZIF-8和ZIF-67吸附碘后的Mapping图像及EDS图谱

Fig. 4 Mapping images and EDS patterns of ZIF-8 and ZIF-67 (a) Mapping image of ZIF-8 after adsorption iodine; (b) Mapping image of ZIF-67 after adsorption iodine; (c) EDS pattern of ZIF-8 after adsorption iodine; (d) EDS pattern of ZIF-67 after adsorption iodine

图5 ZIF-8(a)及ZIF-67(b)的热重曲线

Fig. 5 TGA curves of ZIF-8 (a) and ZIF-67 (b)

图6 ZIF-8(a)及ZIF-67 (b)的氮气吸脱附曲线

Fig. 6 Nitrogen adsorption and desorption curves of ZIF-8 (a) and ZIF-67 (b)

图7 ZIF-8(a)及ZIF-67(b)的吸附量随溶液初始浓度变化曲线图

Fig. 7 ZIF-8 (a) and ZIF-67 (b) adsorption capacity dependences of the initial concentration of the solution

表1 ZIF-8及ZIF-67吸附碘的Langmuir及Freundlich方程参数值

Table 1 Langmuir and Freundlich parameters for adsorption of iodine by ZIF-8 and ZIF-67

		ZIF-8	ZIF-67
Langmuir equation	Q_m/(mg·g^-1)	64416.71	77747.64
	k_L/(L·mg^-1)	1.59×10^-4	1.30×10^-4
	R²	0.99	0.99
Freundlich equation	k_F/(mg·g^-1)	10.00	10.84
	n	1.00	0.98
	R²	1.00	0.99

图8 ZIF-8及ZIF-67对碘的吸附量随时间的变化曲线

Fig. 8 Iodine adsorption capacity dependence of the adsorption time by ZIF-8 and ZIF-67

表2 ZIF-8及ZIF-67吸附I2的准一级及准二级方程参数值

Table 2 Pseudo first and pseudo second order kinetics parameters for the adsorption of iodine by ZIF-8 and ZIF-67

		ZIF-8	ZIF-67
Psedo-first-order kinetics equation	Q_e/(mg·g^-1)	1010.54	1047.37
	k₁/(L·mg^-1)	1.30×10^-4	1.49×10^-4
	R²	0.97	0.93
Psedo-second-order kinetics equation	Q_e/(mg·g^-1)	947.61	916.08
	k₂/(g·min^-1·mg^-1)	0.08	0.12
	R²	0.99	0.96

图9 ZIF-8及ZIF-67对碘的吸附机理示意图

Fig. 9 Adsorption mechanism of iodine on ZIF-8 and ZIF-67

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