Study on the Preparation and Fluoride Removal of Zn⁃Mg⁃Al LDO

doi:10.12422/j.issn.1006-396X.2023.05.010

Abstract

Abstract:

The semiconductor, electroplating, metallurgy, and ceramic industries discharge high concentration fluoride containing wastewater, making fluoride pollution in natural water a global problem.Thus， Zn?Mg?Al LDO is a good adsorbent material. Under different reaction temperatures of n（Zn²⁺）/n（Mg²⁺）/n（Al³⁺）, Zn?Mg?Al LDH was synthesized by co?precipitation method, and Zn?Mg?Al?LDH was calcined at different temperatures to obtain Zn?Mg?Al?LDO. X?ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT?IR) and BET specific surface area testing methods were used to study the structure and properties of Zn?Mg?Al LDO. The adsorption experiment was conducted on 50 mL of NaF solution with an mass concentration of 20.0 mg/L to investigate the performance of Zn?Mg?Al LDO in adsorbing and removing fluoride ions. The results showed that the Zn?Mg?Al LDO prepared under the conditions of n（Zn²⁺）/n（Mg²⁺）/n（Al³⁺）=2∶1∶1, reaction temperature of 75 ℃, and calcination temperature of 400 ℃ exhibited the best adsorption and removal performance of fluoride ions, with an adsorption and removal rate of 85.39%. Zn?Mg?Al LDO has characteristic peaks of hydrotalcite, good crystal structure, and a layered structure. Zn?Mg?Al LDO is a mesoporous material with a specific surface area of 103.15 m²/g. In addition, the kinetics and adsorption mechanism of the adsorption process were also studied. The results indicate that the adsorption process follows the Langmuir adsorption isotherm and quasi second?order kinetic equation.

Key words: Zn?Mg?Al hydrotalcite, Kind of hydrotalcit, Adsorbent, Fluorine, Layered double hydroxide

摘要：

半导体、电镀、冶金和陶瓷行业排放高浓度含氟废水，因此天然水中的氟化物污染已成为一个全球性问题，而Zn?Mg?Al LDO是很好的吸附材料。在n（Zn²⁺）/n（Mg²⁺）/n（Al³⁺）、反应温度不同的条件下，采用共沉淀法合成Zn?Mg?Al LDH，并将Zn?Mg?Al LDH在不同温度下焙烧制得Zn?Mg?Al LDO；利用X射线衍射（XRD）、扫描电子显微镜（SEM）、傅里叶变换红外光谱（FT?IR）、BET比表面积测试法等方法，探究了Zn?Mg?Al LDO的结构和性质；对50 mL质量浓度为20.0 mg/L的NaF溶液进行吸附实验，考察了Zn?Mg?Al LDO吸附去除氟离子的性能。结果表明，在n（Zn²⁺）/n（Mg²⁺）/n（Al³⁺）＝2∶1∶1、反应温度为75 ℃、焙烧温度为400 ℃的条件下制备的Zn?Mg?Al LDO吸附去除氟离子的性能最好，氟离子的吸附去除率达到85.39%；Zn?Mg?Al LDO具有水滑石特征峰，晶型良好，呈层状结构；Zn?Mg?Al LDO为介孔材料，其比表面积为103.15 m²/g。此外，还研究了吸附过程的动力学和吸附机理。结果表明，吸附过程符合Langmuir吸附等温线和准二级动力学方程。

关键词: 锌镁铝水滑石, 类水滑石, 吸附剂, 氟, 层状双氢氧化物

CLC Number:

TB332

Min LI, Zheng LI, Guizhou GU, Xiyang YU, Hui WANG. Study on the Preparation and Fluoride Removal of Zn⁃Mg⁃Al LDO[J]. Journal of Petrochemical Universities, 2023, 36(5): 73-80.

李敏, 李政, 顾贵洲, 于喜洋, 王辉. Zn⁃Mg⁃Al LDO的制备及其除氟性能研究[J]. 石油化工高等学校学报, 2023, 36(5): 73-80.

Figures/Tables 17

Fig.1 XRD patterns of Zn?Mg?Al LDO

Table 1 Crystal parameters of Zn?Mg?Al LDO

参数	数值
d₀₀₃/nm	0.766 4
d₁₁₀/nm	0.177 3
a/nm	0.354 6
c/nm	2.299 2

Fig.2 SEM images of Zn?Mg?Al LDO before and after adsorption

Fig.3 FT?IR spectra of Zn?Mg?Al LDO

Table 2 BET calculations of specific surface area, pore size, and pore volume of Zn?Mg?Al LDO

参数	数值
比表面积/(m²·g^-1)	103.15
孔径/nm	27.26
孔容/(mL·g^-1)	0.702 4

Fig.4 Adsorption?desorption isotherm of Zn?Mg?Al LDO

Fig.5 Effect of n(Zn2+)/n(Mg2+) on the adsorption performance of Zn?Mg?Al LDO

Fig.6 Effect of reaction temperature on athe adsorption performance of Zn?Mg?Al LDO

Fig.7 Effect of calcination temperature on adsorption performance

Fig.8 Effect of Zn?Mg?Al LDO dosage on adsorption performance

Fig.9 Effect of NaF mass concentration on adsorption properties

Fig.10 Effect of pH of solution on the adsorption performance of Zn?Mg?Al LDO

Fig.11 Effect of cycle regeneration times on the adsorption performance of Zn?Mg?Al LDO

Fig.12 Mg?Al?Fe LDO quasi?first?order and quasi?second-order dynamic equations

Table 3 Adsorption kinetic model parameters

温度

/℃

拟一级动力学方程

拟二级动力学方程

k₁/min^-1

12

k₂/(g·mg^-1·min^-1)

22