編號： 11
研 究 生：張家銘 Chang Chia-Ming
論文名稱：北臺灣與澎湖島紅壤中鐵凎氧磁性氧化鐵之鑑定以及尖晶石型式鐵與鋁氧化物表面去質子化反應的量子化學研究
Characterization of Ferrimagnetic Iron Oxides in Red Soils of Northern Taiwan and Peng-Hu Island, and Quantum-Chemical Studies on the Deprotonation of Spinel-Type Iron and Aluminum Oxide Surfaces
指導教授：王明光 Wang Ming-Kuang
學位類別：博士
校院系所： 國立臺灣大學農業化學研究所土壤環境與植物營養組
學 年 度： 85
出 版 年：民 86
論文頁數： 146
〔摘要〕
結合溼式化學、 X- 射線繞射鑑定與鐵 -57 梅思堡光譜分析，以及超導量子干涉磁化儀之磁化曲線測量等研究方法，得以獲知致使北台灣與澎湖島紅壤具有強磁性的礦物物種，主要乃為屬於尖晶石型式之鐵淦氧磁性鐵氧化物；另由於北台灣安山岩質強磁性紅壤經手執磁鐵分離後之強磁性部份的亞鐵離子含量遠高於澎湖島玄武岩質強磁性紅壤，且由鐵 -57 梅思堡分析之直接研究證據顯示，北台灣淡水、八里安山岩質強磁性紅壤中之尖晶石型式鐵氧化物應屬部份氧化之磁鐵礦，澎湖島東衛、外垵玄武岩質強磁性紅壤中的尖晶石型式鐵氧化物則屬磁赤鐵礦，從飽和磁化量與低磁場磁化率之分析結果得以判斷北台灣與澎湖島強磁性紅壤中的鐵淦氧磁性氧化鐵相對含量多寡以淡水＞東衛＞八里＞外垵；各剖面層次之相互比較為：淡水： B2 層＞ B1 層＞ A 層，八里： A 層＞ B1 層＞ B2 層，東衛： A 層＞ B2 層＞ B1 層，外垵： B2 層＞ B1 層＞ A 層；而從高磁場磁化率則判斷得知東衛紅壤中順磁性礦物之相對含量遠較淡水、八里與外垵三處為高；不同粒徑部份的相互比較則為：淡水：砂粒＞坋粒＞黏粒，八里 : 坋粒＞黏粒＞砂粒，東衛：黏粒＞坋粒＞砂粒，外垵：黏粒＞坋粒＞砂粒。
本論文並引進量子化學中，由第一原理出發之密度泛函理論 (density functional theory, DFT) 計算，以明瞭與水合金屬陽離子和金屬氧化物表面之去質子反應進行難易密切相關的各項分子層次特性。
研究結果發現，以 VWN(Vosko-Wilk-Nusair functional) ， BP(Becke-Perdew functional) 與 BLYP(Becke-Lee-Yang-Parr functional) 等不同密度泛函所計算而得之結構穩定度計算值 (binding energy, Ebind) ，得以整体考慮鎂 ( Ⅱ ) 、鈣 ( Ⅱ ) 、錳 ( Ⅱ ) 、鋅 ( Ⅱ ) 、鎘 ( Ⅱ ) 、鋁 ( Ⅲ ) 、鈧 ( Ⅲ ) 、鉻 ( Ⅲ ) 、鐵 ( Ⅲ ) 、鎵 ( Ⅲ ) 與銦 ( Ⅲ ) 等主要元素族與過渡元素族六水金屬陽離子的去質子化反應，其與第一水解常數實驗觀測值 (pKa) 之線性關係與直線迴歸係數 (r) 為 :VWN 密度泛函 : pKa = -19.15 + 0.02 Ebind r = 0.96 BP 密度泛函 : pKa = -12.93 + 0.02 Ebind r 0.96 BLYP 密度泛函 : pKa = -13.08 + 0.02 Ebind r = 0.97 而經由六水金屬陽離子結構穩定度與金屬陽離子配位能 (coordination energy, Ecoord) 的聯繫 :VWN 密度泛函 : Ecoord = -1890.92 + 1.16 Ebind r = 0.96 BP 密度泛函 : Ecoord = -1436.61 + 1.03 Ebind r = 0.96 BLYP 密度泛函 : Ecoord = -1441.75 + 1.03 Ebind r = 0.96 獲知六水金屬陽離子第一水常數實驗觀測值與金屬陽離子配位能之間的線性關係為 :VWN 密度泛函 : pKa = 16.58 + 0.02 Ecoord r = 0.96 BP 密度泛函 : pKa = 15.73 + 0.02 Ecoord r = 0.95 BLYP 密度泛函 : pKa = 15.94 + 0.02 Ecoord r = 0.96 以密度泛函理論計算當一外來水分子與六水鐵 (III) 、鋁 (III) 、錳 (II) 或鎂 (II) 離子產生聯結反應平衡後之聯結反應能量變化量， O-H 鍵長伸長量與外來水分子的密立根電荷重配量，獲知當六水金屬陽離子之去質子化反應愈易進行，則聯結反應放熱值愈大， O-H 鍵長伸長量愈長，且外來水分子的密立根電荷重配程度亦愈明顯，致使外來水分子所帶之淨電荷愈趨正電性；另並分析六水金屬陽離子之紅外線簡諧振動頻率，由 O-H 伸縮振動頻率計算值得以判斷六水金屬陽離子之去質子化反應進行難易，當 O-H 伸縮振動頻率愈高，則 O-H 鍵結愈強，去質子化反應愈難進行。
在六水金屬陽離子去質子化反應之密度泛函理論計算結果基礎下，配合分子顆團模型模擬計算其結構穩定度、去質子化反應能量與 O-H 伸縮振動頻率獲知尖晶石型式鐵、鋁氧化物表面之氫離子吸附親合力常數以鋁氧化物＞鐵氧化物，八面体配位座落＞四面体配位座落。
Combined with the wet chemistry, X-ray diffraction (XRD), Fe-57 Mossbauer analysis and superconducting quantum interference device (SQUID) investigation, the magnetic minerals existed in Northern Taiwan and Peng-Hu Island red soils can be identified as ferrimagnetic (spinel-type) iron oxides. Owing to the high Fe2+ content in the hand magnetic fractions of Northern Taiwan red soils and the evidence provided by Fe-57 Mossbauer analysis, the species of spinel-type iron oxides in Tan-Shui and Pa-Li red soils was characterized as the partially oxidized magnetite. However, the iron oxide in Tung-Wei and Wai-An red soils was predominated in maghemite. According to the saturated magnetization and low field susceptibility, the relative content of ferrimagnetic iron oxides in Northern Taiwan and Peng-Hu red soils can be summarized as follows: (1) Tan-Shui > Tung-Wei > Pa-Li > Wai-An; (2) Tan-Shui: B2 horizon > B1 horizon > A horizon; Pa-Li: A horizon > B1 horizon > B2 horizon; Tung-Wei: A horizon > B2 horizon > B1 horizon; Wai-An: B2 horizon > B1 horizon > A horizon; (3) Tan-Shui: Sand > Silt > Clay; Pa-Li: Silt > Caly > Sand; Tung-Wei: Clay > Silt > Sand; Wai-An: Clay > Silt > Sand. Furthermore, the high field susceptibility implies that the relative content of paramagnetic minerals in Tung-Wei red soils is higher than that in Tan-Shui , Pa -Li and Wai-An red soils.
In this study , the deprotonated characteristics of aqueous metal ions and metal oxide surfaces in molecular level can be clarified by applying the first-principles density functional theory (DFT). From the binding energies (Ebind) calculated with Vosko-Wilk-Nusair (VWN), Becke-Perdew (BP) and Becke-Lee-Yang-Parr (BLYP) density functionals, the global linear relationship for the acidity and stability in both main group (Mg(II), Ca(II) and Al(III)) and (post-)transition group
(Mn(II), Zn(II), Cd(II), Sc(III), CR(III), Fe(III), Ga(III) and In (III)) aqueous metal ions has been confirmed:
VWN density functional: pKa = -19.15 + 0.02 Ebind r = 0.96
BP density functional: pKa = -12.93 + 0.02 Ebind r = 0.96
BLYP density functional: pKa = -13.08 + 0.02 Ebind r =0.97
via the linkage of the correlation for binding and coordination energies (Ecoord):
VWN density functional:Ecoord = -1890.92 + 1.16 Ebind r = 0.96
BP density functional: Ecoord = -1436.61 + 1.03 Ebind r = 0.96
BLYP density functional: Ecoord = -1441.75 + 1.03 Ebind r =0.96
the linear relationship between first hydrolysis constants and coordination energies in hexaaqua metal ions can be obtained:
VWN density functional: pKa = 16.58 + 0.02 Ecoord r = 0.96
BP density functional: pKa = 15.73 + 0.02 Ecoord r = 0.95
BLYP density functional: pKa = 15.94 + 0.02 Ecoord r = 0.96
Density functional calculations were also conducted to elucidate the reaction of a foreign water molecule associated with a hexaaqua Fe(III), Al(III), Mn(II) or Mg(II) ion. The result presents that more remarkable variation in the exothermic energy change, O-H bond lengthening and Mulliken charge redistribution is favorable for the progression of the deprotonation of hexaaqua metal ions. Moreover, judging from the calculated O-H stretching vibrational frequencies of hexaaqua metal ions, the larger the vibrational frequency, the more difficult the deprotonation progression.
On the basis of previous density functional results regarding the deprotonation of aqueous metal ions, the tructural stability, deprotonation energy and O-H stretching vibrational frequency of the molecular cluster model of octahedral and tetrahedral sites on spinel-type Fe and Al oxide surfaces were further examined. The sequence of the proton adsorption affinity shows in the order of Al oxide > Fe oxide; octahedral site > tetrahedral site.
