利用層狀複合金屬氫氧化物即時合成與鍛燒之記憶效應去除水中硝酸鹽之研究

A study on removal of nitrate using layer double hydroxides through in situ synthesis and memory effect

張峰銘(FENG-MING ZHANG)

指導教授 ： 趙煥平

中原大學/工學院/環境工程學系/碩士(2020年)

https://doi.org/10.6840/cycu202000593

摘要

水中硝酸鹽的污染日趨嚴重，若未經妥善處置進入水體，對人體抑或是環境，都會造成危害，但硝酸鹽無法以沉澱處理且不易以礦物吸附，因此本研究中選擇層狀金屬氫氧化物去除水中硝酸鹽，其主要利用Mg2+與Al3+金屬陽離子，以及CO32-等陰離子進行合成，在本研究中利用即時合成方式，在不同pH值溶液條件下，將Mg2+與Al3+的莫耳比控制在3:1之濃度範圍內，與陰離子加入溶液中與濃度不同之硝酸鹽混合，試驗紀錄在不同時間條件下硝酸鹽之濃度變化，再計算出吸附過程中的吸附效率及最大吸附量。而後以水熱合成法製備出層狀複合金屬氫氧化物，再因其具有記憶效應之特性，將所合成之材料於不同溫度下鍛燒，待冷卻過後將合成之材料與硝酸鹽溶液攪拌混合，於不同時間下取樣分析測定溶液中硝酸鹽濃度的變化，再計算得出其吸附過程中吸附之速率與最大的吸附容量數值。
在本次研究試驗中以水熱合成法合成LDHs，然後在300、400與500 oC下鍛燒合成LDHs-C300、LDHs-C400、LDHs-C500共三種吸附劑，分別分析其表面性質確定所合成的吸附劑的特性，在等溫吸附試驗的吸附結果皆符合Langmuir model，四種吸附劑之最大吸附量分別為：73.4(mg/g)、182(mg/g)、196(mg/g)、384(mg/g)；而在動力吸附試驗之結果則符合擬二階吸附動力方程式，吸附成效結果顯示：LDHs-C500> LDHs-C400> LDHs-C300> LDHs。另外透過即時合成法去除水中硝酸鹽之最佳加藥量則為：Group3：0.012 mol MgCl․6H2O、0.004 mol AlCl3․9H2O、0.0336 mol NaOH、0.0022 mol Na2CO3。所獲得結果建議LDHs可以配合生物或其他處理方式有效去除水中硝酸鹽。

關鍵字

層狀複合金屬氫氧化物、硝酸鹽、吸附、即時合成、鍛燒記憶效應

並列摘要

The nitrate contamination in water has become an important issue in recent days. When the nitrate was discharged into water bodies, it might cause significant harm to human bodies. Nitrate is difficultly removed through precipitation or adsorption. For the reason, layer double hydroxides(LDHs) were developed to remove nitrate in water. Mg2+, Al3+ and CO32- are mainly ingredients to form (LDHs). In this study, real-time synthesis methods was used with the mole ratio of Mg2+ and Al3+ to be 3:1, under different solution pH conditions. Anions are then added to the solution with different nitrate concentrations. The nitrate concentrations are measured in the given time. The adsorption efficiency and the maximum absorption capacity of produced LDHs toward nitrate are calculated. Afterwards, layered double hydroxides are produced using hydrothermal synthesis methods, the synthesized materials are calcined under different temperatures. Based on their memory effect characteristics, the calcined materials mixed with the nitrate solution, can reproduce LDHs with higher adsorption capacities. The kinetic and equilibrium adsorption experiments were carried out to estimate adsorption efficiency and the maximum absorption amount.

In addition, LDHs was synthesized through the hydrothermal method, and then the LDHs was calcined under 300, 400 and 500oC to produce LDHs-C300, LDHs-C400 and LDHs-C500, respectively. The four adsorbents were characterized using the instruments to determine surface properties. The result of this research shows that isotherms for adsorption of nitrate on the four adsorbents can fit Langmuir model. The maximum absorption amount for the four absorbents are 73.4(mg/g), 182(mg/g), 196(mg/g) and 384(mg/g), respectively. The result of the kinetic absorption experiment can fit the pseudo second order kinetics. The absorption effect results indicate that LDHs-C500> LDHs-C400> LDHs-C300> LDHs. Furthermore, the optimal dosage to remove nitrate in water using real-time synthesis methods is Group3: 0.012 mol MgCl․6H2O, 0.004 mol AlCl3․9H2O, 0.0336 mol NaOH and 0.0022 mol Na2CO3. The results indicated the LDHs together the other processes can effectively remove the nitrate in water or wastewater.

並列關鍵字

layered double hydroxides, nitrate, absorption, real-time synthesis, calcination memory effect

參考文獻

參考文獻

1. 曾雨凡，「選擇性光催化還原水中硝酸鹽為氮氣之研究」，國立臺灣大學環境工程學研究所，2007。

2. Rivett, M.O., Buss, S.R., Morgan, P., Smith, J.W.N., Bemment, C.D.(2008) Nitrate attenuation in groundwater: A review of biogeochemical controlling processes. Water Resarch 42(16), 4215-4232.

3. Almasri, M.N., Kaluarachchi, J.J. (2007) Modeling nitrate contamination of groundwater in agricultural watersheds. Journal of Hydrology 343(3–4), 211-229.

4. Azizullah, A., Khattak, M.N.K., Richter, P., Häder, D.-P. (2011) Water pollution in Pakistan and its impact on public health — A review. Environment International 37(2), 479-497.