Sustainable synthesis of ZSM-5 zeolite from iron ore tailings
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摘要: 针对河北承德某地区铁尾矿硅铝含量高的特点，以该尾矿为原料制备ZSM-5分子筛。目前，以固体废弃物为原料合成分子筛通常采用水热法，合成工艺复杂、单釜利用率低且产生废水，严重限制了以固体废弃物为原料合成分子筛的大规模应用。该研究提出以无溶剂法合成ZSM-5分子筛，在分子筛合成过程中无液体溶剂参与，因此更加绿色环保。研究表明，ZSM-5分子筛最佳合成参数为：HDA/SiO2=0.1、Na2CO3·10H2O/SiO2=0.4，150 °C晶化6 d，此时得到的ZSM-5分子筛同时具有介、微复合孔结构，其中微孔表面积为213.2 m2/g，外表面积为95.53 m2/g。此外，无溶剂法合成分子筛的元素利用率高于传统水热法，无溶剂法Si和Al的元素利用率分别为94.83%、95.89%，而水热法仅为80%左右。Abstract: In view of the high silicon and aluminum content of iron ore tailings (IOT) in Chengde, Hebei province, ZSM-5 zeolite was prepared with IOT as the raw materials. At present, the synthesis of zeolite from solid waste usually uses hydrothermal method, which is a complex synthesis process with low utilization rate of single reactor and produces wastewater. Our approach focused on reutilization of IOT by converting it to ZSM-5 via solvent-free method. It shows that the optimal synthesis parameters of ZSM-5 zeolite are HDA/SiO2=0.1, Na2CO3·10H2O/SiO2=0.4, and crystallization at 150 ℃ for 6 days. The obtained ZSM-5 zeolite has bimodal meso- and micro-porous structure, with a surface area of micropores of 213.25 m2∙g−1 and an external surface area of 95.53 m2∙g−1. In addition, the elemental utilization rate of the solvent-free method is higher than that of the conventional hydrothermal method, and the elemental utilization rates of Si and Al for the solvent-free method are 94.83% and 95.89%, respectively, while those for the hydrothermal method were only 80%.
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Key words:
- iron ore tailings /
- ZSM-5 zeolite /
- solvent-free method /
- crystallization time /
- surface area
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图 1 铁尾矿无溶剂制备ZSM-5分子筛示意
Figure 1. Schematic diagram of solvent-free preparation of ZSM-5 molecular sieve from IOT
图 2 不同晶化时间产物的XRD谱
Figure 2. XRD patterns of products with different crystallization time
图 3 不同晶化时间样品的SEM-EDS图像
Figure 3. SEM-EDS images of samples at different crystallization time
图 4 不同Na2CO3·10H2O/SiO2摩尔比样品XRD谱
Figure 4. XRD patterns of samples with different Na2CO3·10H2O/SiO2 molar ratios
图 5 不同HDA/SiO2摩尔比产物的XRD谱
Figure 5. XRD patterns of products with different HDA/SiO2 molar ratios
图 6 铁尾矿、ZSM-5分子筛的氮气吸附脱附曲线（a）和BJH吸附孔径分布（b）
Figure 6. N2 adsorption–desorption isotherms (a) and BJH adsorption pore distributions (b) of IOT and ZSM-5 zeolite
表 1 预处理前后铁尾矿成分
Table 1. The compositions of IOT before and after treatment
% SiO2 Al2O3 杂质 Fe2O3 CaO K2O MgO Na2O 预处理前 68.64 13.14 9.47 3.41 2.24 2.26 0.74 预处理后 91.91 1.51 2.49 1.10 0.49 0.60 1.79 
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表 2 铁尾矿和ZSM-5分子筛的吸脱附数据
Table 2. Physicochemical properties of IOT and ZSM-5 zeolite
比表面积/
( m2∙g−1)微孔表面积/
( m2∙g−1)外表面积/
( m2∙g−1)孔体积/
(cm3∙g−1)微孔体积/
( cm3∙g−1)介孔体积/
(cm3∙g−1)BJH吸附平均
直径/nm铁尾矿 26.51 1.08 25.43 0.042 0.042 2.142 ZSM-5 分子筛 308.78 213.25 95.53 0.196 0.1104 0.092 4.587
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