Zeolite Synthesis under Insertion of Silica Rich Filtration Residues from Industrial Wastewater Reconditioning
Zeolite Synthesis under Insertion of Silica Rich Filtration Residues from Industrial Wastewater Reconditioning
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DOI：
10.4236/aces.2014.42015
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发表时间：
2014-04
期刊：
影响因子：
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通讯作者：
A. Hartmann;V. Petrov;J. Buhl;K. Rübner;M. Lindemann;C. Prinz;A. Zimathies
中科院分区：
文献类型：
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作者：
A. Hartmann;V. Petrov;J. Buhl;K. Rübner;M. Lindemann;C. Prinz;A. Zimathies
以富硅过滤残渣(FR-1和FR-2)为硅源，铝酸钠为硅源，在60℃强碱性条件下(8M-16M NaOH)直接合成沸石。除了这些一锅法合成外，还研究了两步法工艺。在60℃下碱解FR，然后用铝酸钠进行凝胶沉淀，在80℃-90℃的通常条件下凝胶结晶。结果表明，用像FR这样的废料代替化学试剂硅酸钠作为硅源是可行的，但需要微调反应条件，因为沸石结晶是一个受动力学控制的过程。插入的过滤残留物的溶解行为和杂质对反应过程有很大影响。因此，在一锅法合成中，根据碱度的不同，在1-4h的短时间内就可以观察到类似水钠石或介于沸石和钠沸石之间的沸石，或者与水钠石共结晶的NAA或Z-21沸石。两步法可得到质量很好的NaA和NaX沸石。用化学分析、X-射线粉末衍射、傅立叶变换红外光谱和扫描电子显微镜对两种反应方法中的反应过程进行了表征。用BET法和热重法对所选产物的比表面积和水分含量进行了进一步表征。综上所述，我们可以通过几个反应步骤从过滤残渣中生成沸石，作为工业废物再利用的典范案例。除了对环境保护的重要性外，这些反应对沸石化学也很有意义，因为在60℃下能耗低、反应周期短的经济条件下，可以重复使用FR。
Zeolite synthesis was studied using two silica rich filtration residues (FR 1 and FR 2) as Si-source and sodium aluminate in a direct synthesis at 60°C at strong alkaline conditions (8 M - 16 M NaOH). In addition to these one-pot syntheses, a two-step process was investigated. Here, an alkaline digestion of FR at 60°C was followed by gel precipitation with sodium aluminate and gel crystallization under usual conditions of 80°C - 90°C. The results show that the substitution of chemical reagent sodium silicate by a waste material like FR as Si-source is possible but requires fine tuning of the reaction conditions as zeolite crystallization is a process under kinetic control. The solubility behaviour and impurities of the inserted filtration residues strongly influenced the course of reaction. Thus zeolites like hydrosodalite or intermediate zeolite between cancrinite and sodalite, or zeolite NaA or Z-21 in cocrystallization with hydrosodalite could be observed in the one pot syntheses already in a short time interval between 1 - 4 h depending on the alkalinity. The two step process yield to zeolites NaA and NaX in very good quality. The reaction process of FR in both reaction methods was characterized by chemical analyses, X-ray powder diffraction, Fourier transform infrared spectroscopy as well as scanning electron microscopy. Surface area and water content of selected products were further characterized by the BET-method and by thermogravimetry. Summing up the results, we can show that zeolite formation from filtration residues is possible by several reaction procedures as model cases for a re-use of industrial waste materials. Beside the importance for environmental protection, the reactions are of interest for zeolite chemistry as the re-use of FR is possible under economically conditions of low energy consumption at 60°C and short reaction periods.