利用胺基酸改質鎂鋁層狀複合金屬吸附鉻和鉻酸鹽之研究之研究

本研究利用共沉澱法合成鎂鋁層狀複合金屬氫氧化物，在合成材料的同時將苯丙胺酸、酪胺酸、絲胺酸三種胺基酸等有機酸陰離子，以不同的濃度插層至鎂鋁層狀複合金屬，並以此改質之吸附劑在pH= 4與5 的條件下吸附溶液中之重金屬。製備完成之吸附劑利用SEM、FTIR、XPS、XRD來鑑定其性質，再利用吸附平衡計算對六價鉻與三價鉻重金屬離子之吸附容量並探討可能的吸附機制。研究結果顯示Mg與Al之莫耳比為3:1，且胺基酸已成功插層至鎂鋁層狀複合金屬氫氧化物，但吸附劑層間仍保有碳酸鹽存在。因此所合成之吸附劑可以利用陰離子交換吸附水中六價的鉻酸鹽，同時也可以利用胺基酸所形成的錯合反應吸附水中三價鉻，同時對於兩種污染物皆可獲得高吸附容量。鉻酸鹽在pH=4呈現較佳吸附量，三價鉻則在pH=5有較佳吸附量，有機插陰離子插層濃度高有利於三價鉻吸附，插層濃度低則有利六價鉻吸附，三價鉻以苯丙胺酸插層可獲得較佳吸附容量，而六價鉻以酪胺酸插層可獲得較佳吸附量。本次實驗吸附劑最大的特點，為發展可以同時吸附陰離子鉻酸鹽與陽離子三價鉻之吸附劑，且所使用的材料均為成本較低的物質，又具備高吸附量，與離子交換樹脂比較未來將具備價格的發展優勢。

關鍵字

鎂鋁層狀複合金屬；胺基酸；吸附；鉻酸鹽；三價鉻

並列摘要

Mg-Al layered double hydroxides (Mg-Al LDHs) was produced using a co-precipitation method and intercalated with amino acids including phenylalanine, tyrosine and serine. The obtained materials were used to adsorb the cationic heavy metals (Cr3+) and the oxyanion (Cr6+) from aqueous solution under solution pH 4 and 5. The adsorbents were characterized by XPS, SEM, FTIR and XRD. The maximum adsorption capacities of adsorbents under the given conditions were estimated from Langmuir equation. Moreover, the potential adsorption mechanisms of the adsorbents toward the heavy metal ions were elucidated. The results indicated Mg-Al LDHs have been synthesized and amino acids have been entered the interlayer. The molar ratio of Mg and Al is 3 according to the result in XPS. In addition, carbonate was found in the interlayer through FTIR. As a result, the adsorbents can adsorb chromium ion through the complexation reaction. Dichromate can be adsorbed through anion exchange process. The produced adsorbents can generate the high adsorptive amount for the target pollutants. The relatively higher adsorption amount for dichromate was found under pH 4. The solution pH increases to 5 that favor the adsorption of chromium ion. The high intercalated concentrations of amino acid lead to the higher adsorptive amount for chromium ion. The low intercalated concentrations can increase the adsorptive amount for dichromate. The maximum capacity of chromium ion and dichromate were found phenylalanine and tyrosine intercalation, respectively. The advantage of this experimental adsorbent is to develop an adsorbent to simultaneously adsorb anionic chromate and cationic trivalent chromium at the same time. The produced materials used are low cost and high adsorption capacity. Compared with ion exchange resin, the adsorbents possess the advantage in the low cost.

並列關鍵字

Mg-Al layered double hydroxide ； Amino acids ； Adsorption；Dichromate；Chromium.

參考文獻

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[2]K. H. Goh, T. T. Lim, Z. Dong, 2007. Application of layered double hydroxides for removal of oxyanions: A review. Water Res. 42, 1343–1368.

[3]F. Kooli, K. Kosuge, A. Tsunashima, 1995. New Ni-Al-Cr and Ni-Al-Fe Carbonate Hydrotalcite-like Compounds: Synthesis and Characterization. J. Solid State Chem. 118 (2), 285–291.

[4]S. P. Newman, W. Jones, 1998. Synthesis, characterization and applications of layered double hydroxides containing organic guests. New J. Chem. 22 (2), 105–115.

[5]J. He, M. Wei, B. Li, Y. Kang, D. G. Evans, X. Duan, 2006. Preparation of layered double hydroxides. Struct. Bond. 119 (1), 89–119.

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利用胺基酸改質鎂鋁層狀複合金屬吸附鉻和鉻酸鹽之研究之研究

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