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  • 學位論文

四尾柵藻吸附水中稀土離子的性能研究

Recovery of Rare Earth Ions from Water by Utilizing Scenedesmus quadricauda

指導教授 : 于昌平
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摘要


近年來稀土產業鏈快速發展,全球稀土儲量大幅減少,稀土污染也隨之而至。利用環境生物技術從環境中回收稀土離子近年來得到了廣泛的關注。其中,利用藻類去吸附稀土離子是一種較為新穎的技術。 本研究利用四尾柵藻去吸附水中的稀土離子,以吸附率及微藻單位吸附容量為衡量指標,考察了在不同的反應條件下四尾柵藻對Nd3+、Eu3+、Gd3+的吸附性能。研究發現,四尾柵藻對三種稀土離子的吸附動力學擬合較好的為擬二級動力學模型(R^2≈0.999),表明了物質擴散步驟對吸附效率的影響可以忽略,限速步驟主要是化學吸附過程;吸附等溫線擬合較好的為Langmuir方程(R^2≈0.999);而在熱力學研究中,擬合可得∆G^0均為負值,∆S^0、∆H^0均為正值,該吸附過程為自發吸熱過程。溶液初始pH值對微藻細胞壁的官能團的活性、稀土離子的化學形態有著顯著的影響,本研究發現,當溶液初始pH為4~8時,吸附容量隨著pH值的上升而增加,因為pH較低時,靜電作用導致H+與稀土離子競爭吸附位點,pH較高時細胞表面官能團去質子化能更好吸附稀土。因為活藻吸附涉及主動運輸,研究發現光照條件下的吸附效果略好於黑暗條件。最後經由SEM-EDX、FTIR表征分析可知,微藻細胞上富含羥基、氨基、羧基、酰胺基、羰基,可與稀土離子發生離子交換、絡合作用。 此外,本研究進一步評估出在合適的環境下進行吸附實驗,即反應溫度為30 ℃、藻濃度為0.3 g/L、初始稀土離子濃度約為50 mg/L、初始pH=8.00(±0.03)時,微藻對Nd3+、Eu3+、Gd3+的吸附容量分別可達134.82 mg/L、150.66 mg/L、142.69 mg/L。在解吸研究中,發現使用0.01 M EDTA溶液可在不對微藻造成破壞性的前提下,有效脫附微藻所吸附稀土離子,解吸率分別為97.66%、98.12%、98.01%。 同時,在稀土離子對四尾柵藻的脅迫作用的研究中,發現低濃度稀土離子可刺激微藻生長繁殖,而高濃度將會抑制其生長。三種離子中,對四尾柵藻毒性最強的為Gd3+。 通過以上研究發現四尾柵藻是一種高效且低成本的生物吸附材料,對Nd3+、Eu3+、Gd3+的吸附去除率可達到99%以上,而且可以利用EDTA溶液對稀土離子進行回收。

並列摘要


In recent years, the rapid development of the rare earth industry chain has led to a significant reduction in global rare earth reserves, which has also resulted in rare earth pollution. The use of environmental biotechnology to recover rare earth ions from the environment has received widespread attention, and the adsorption of rare-earth ions by algae is a new technology. In this study, we successfully used Scenedesmus quadricauda to absorb rare earth ions from water. The adsorption rate and the unit adsorption capacity of microalgae were taken as the indexes to investigate the Nd3+, Eu3+ and Gd3+ adsorption performance of Scenedesmus quadricauda under different reaction conditions. It is found that the pseudo-second-order kinetic model (R2 ≈ 0.999) can better fit the Nd3+, Eu3+ and Gd3+ adsorption kinetics of Scenedesmus quadricauda, which indicated that the speed limiting step is mainly a chemisorption process. The adsorption isotherms are well represented by both the Langmuir model (R2 ≈ 0.999). In the thermodynamic study, the fitting results show that ∆G^0 is negative, while both ∆S^0 and ∆H^0 are positive, proving that the adsorption process is a spontaneous endothermic reaction. The initial pH value of the solution significantly influences the activity of the functional groups and the chemical speciation of rare earth ions. It is found during the study that with increasing pH value of the solution between 4 and 8, the adsorption capacity increases. That is because H+ competes with rare earth ions for adsorption sites due to electrostatic interaction at low pH, and the functional groups on the cell surface better adsorb rare earth ions due to their deprotonization at high pH. The adsorption of living algae involves active transport, so it is found that the adsorption effect is slightly better in the light than in the dark. Finally, SEM-EDX and FTIR analysis shows that the microalgae cells contain a lot of hydroxyl, amino, carboxyl, amide, carbonyl groups, etc., which can react with the rare earth ions by exchange and complexation. In addition, the absorption experiments were carried out under the appropriate conditions. The experimental results show the Nd3+, Eu3+ and Gd3+ adsorption capacity of 0.3 g/L microalgae reach 134.82 mg/L, 150.66 mg/L and 142.69 mg/L at 30 ℃, the rare earth ion concentration of 50 mg/L and initial pH = 8.00 (± 0.03). It is found during the desorption study that 0.01 M EDTA solution could effectively desorb the rare earth ions adsorbed by microalgae without damage to microalgae, with the Nd3+, Eu3++ and Gd3+ desorption rate of 97.66%, 98.12% and 98.01%, respectively. Moreover, it is found during the study on the toxicity of rare earth ions to microalgae that low concentration rare earth ions stimulate microalgae growth and reproduction, whereas high concentration inhibits microalgae growth. Gd3+ has the most toxic effects in Scenedesmus quadricauda among the three ions. Through the above studies, it was found that Scenedesmus quadricauda is an efficient and low-cost bioadsorption material, in which the adsorption rate of Nd3+, Eu3+, Gd3+ can reach more than 99%. After that we can use EDTA solution to recover rare earth ions.

參考文獻


Abdel-Aty, A. M., Ammar, N. S., Ghafar, H. H. A., Ali, R. K. (2013). Biosorption of cadmium and lead from aqueous solution by fresh water alga Anabaena sphaerica biomass. Journal of advanced research, 4(4), 367-374.
Binnemans, K., Jones, P. T., Blanpain, B., Van Gerven, T., Yang, Y., Walton, A., Buchert, M. (2013). Recycling of rare earths: a critical review. Journal of Cleaner Production, 51, 1-22.
Chatterjee, S. K., Bhattacharjee, I., Chandra, G. (2010). Biosorption of heavy metals from industrial waste water by Geobacillus thermodenitrificans. Journal of hazardous materials, 175(1-3), 117-125.
Coimbra, N. V., dos Santos Gonçalves, F., Nascimento, M., Giese, E. C. (2019). Study of adsorption isotherm models on rare earth elements biosorption for separation purposes. Cell, 11(13), 16.
Das, N., Das, D. (2013). Recovery of rare earth metals through biosorption: an overview. Journal of rare earths, 31(10), 933-943.

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