水滑石嵌合亞鐵氰化物材料製備與吸附特性研究

Synthesis and sorption characteristics of hydrotalcite intercalated hexacyanoferrate

李思偉(Szu-Wei Lee)

指導教授 ： 吳紀聖

國立臺灣大學/工學院/化學工程學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202003431

摘要

本研究以水滑石類型材料及亞鐵氰化物材料，應用於放射性廢水處理方法；樣品製備使用低過飽和度共沉澱法，合成鎂-鐵型水滑石嵌合亞鐵氰化物材料；性質鑑定使用X光粉末繞射儀(XRD)、場發射掃描式電子顯微鏡及能量色散X-光光譜(SEM-EDS)及比表面積與孔隙度分析儀(BET)，確認製備樣品結構；吸附特性試驗，使用批次吸附方法，將製備樣品與鍶、銫、鈷離子水溶液混合，並利用原子吸收光譜儀(AA)測量樣品離子濃度，分析材料對不同離子的吸附能力。
合成後的水滑石無機吸附劑擬應用於放射性廢水減量處理，吸附主要關鍵核種如鍶、銫、鈷等；水滑石類材料具有特殊層狀結構，擁有優秀的吸附功能及力學強度，並且容易改質，如調控配比組成；過渡金屬族氰化物對銫離子的吸附能力有高選擇性，然而其力學穩定性低；鎂-鐵型水滑石嵌合亞鐵氰化物類材料據研究顯示具有優秀的鍶離子吸附能力。
本實驗進行水滑石類型結構嵌合錯合物材料之合成製備，合成鎂-鐵型水滑石嵌合亞鐵氰化物，並進行材料特性測試。經分析顯示，所製備樣品具有水滑石結構與亞鐵氰化物結構；吸附特性試驗結果顯示，在200 ppm之試驗離子濃度下，使用0.2 g製備樣品，銫離子經混合16 hr後，溶液離子濃度低於1 ppm；鈷離子經混合4 hr後，溶液離子濃度低於1 ppm；鍶離子吸附率較低，16 hr試驗時間之組別，鍶離子移除比率為83.6%。較高濃度之水溶液試驗結果，使用 Langmuir吸附等溫線擬合，可得此模式假設下所分析之最大吸附量，鍶、銫、鈷離子分別為44.8、82.6及155 mg/dry-g。實驗結果顯示，此材料有良好鍶、銫、鈷離子吸附功能，具有放射性廢水處理應用潛力。

關鍵字

水滑石 ； 亞鐵氰化物 ； 放射性廢水處理 ； 吸附等溫線 ； 吸附作用

並列摘要

In this study, hydrotalcite and ferrocyanide materials were used to develop radioactive wastewater treatment. For preparation of material, low supersaturation co-precipitation method was used to synthesize magnesium-iron hydrotalcite intercalated hexacyanoferrate. For sample analysis and identification, x-ray powder diffractometer (XRD), field-emission scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and specific surface area and porosity analyzer (BET) were used to confirm the structure of the prepared sample. In the sorption property test, batch methods were conducted by mixing the sample with aqueous solution of strontium, cesium, and cobalt ions, respectively, and the atomic absorption spectrometer (AA) was used to measure the concentration of the sample solution. The sorption performance of the sorbent for different ions was then evaluated.
The synthesized hydrotalcite-type inorganic sorbent was applied to the development of the volume reduction treatment of radioactive wastewater by sorption of the main key nuclei, such as strontium, cesium, and cobalt. Hydrotalcite type materials have the layered structure that contribute to excellent sorption functionality and mechanical strength, and the modification is available such as adjusting the proportion of composition. Transition metal hexacyanoferrates have high selectivity for cesium in ion sorption, but have low mechanical stability; research shows that magnesium-iron hydrotalcites intercalated hexacyanoferrates have good sorption capacity toward strontium.
In the study, the synthesis procedure of hydrotalcite type materials was developed to prepare hydrotalcites intercalated hexacyanoferrates, and the sorption property tests were conducted sequently. Analysis results showed both the hydrotalcite structure and the ferrocyanide structure. The sorption property tests showed that, for the condition of ion concentration of 200 ppm mixed with 0.2 g sample, the concentration of cesium was reduced to less than 1 ppm after 16 hours. The concentration of cobalt was reduced to less than 1 ppm after 4 hours. Furthermore, sorption performance of strontium was relatively poor. For the test condition with 16 hours of mixing, the percentage removal of strontium was 83.6%.
For the test solutions with higher concentration, results were fitted with Langmuir adsorption isotherms. The maximum adsorption capacity, analyzed under Langmuir’s assumption, can be obtained: 44.8, 82.6, and 155 mg/dry-g, for strontium, cesium, and cobalt ions, respectively. In conclusion, the experimental result showed that this synthesized material has good sorption performance for strontium, cesium, and cobalt. Therefore, this material has the potential for the application in radioactive wastewater treatment.

並列關鍵字

hydrotalcite ； hexacyanoferrate ； radioactive wastewater treatment ； adsorption isotherm ； sorption process

參考文獻

[1] M. Meyn, K. Beneke, G. Lagaly, Anion-exchange reactions of layered double hydroxides, Inorganic Chemistry, 29 (1990) 5201-5207.

[2] F. Cavani, F. Trifirò, A. Vaccari, Hydrotalcite-type anionic clays: Preparation, properties and applications, Catalysis Today, 11 (1991) 173-301.

[3] G. Fetter, M. Olguín, P. Bosch, S. Bulbulian, Surface Areas of Nitrated Hydrotalcites, Journal of Porous Materials - J POROUS MAT, 7 (2000) 469-473.

[4] K.H. Goh, T.T. Lim, Z. Dong, Application of layered double hydroxides for removal of oxyanions: a review, Water Res, 42 (2008) 1343-1368.

[5] S.J. Mills, A.G. Christy, J.M.R. Génin, T. Kameda, F. Colombo, Nomenclature of the hydrotalcite supergroup: natural layered double hydroxides, Mineralogical Magazine, 76 (2012) 1289-1336.