摘要
焚化飛灰中銅可能具致毒、致癌的潛力(例如銅被懷疑可能導致腦炎和肺癌)及可能與焚化煙道氣之戴奧辛催化生成有關。TCLP(毒性溶出試驗)通常用於規範環境固體污染物之溶出濃度標準，但TCLP只能提供污染物質之濃度數據，缺乏化學結構相關之瞭解，尤其化學萃取的操作相中所發生之特定反應仍尚未清楚；一般應用(EDX、XPS等)方法雖可避免部分限制，但這些方法對偵測微量元素卻通常不夠靈敏，另外某些測定則需調整化學組成或人工添加的方法，以致混亂了數據的解釋。
X射線吸收光譜(XAS)對測定物質中金屬的局部結構和價數變化提供有利分析數據，EXAFS（extended X-ray absorption fine structure）可分析在特定中心原子週遭的結構，包括：配位數、鍵距和氧化狀態，EXAFS提供污染物質之分子結構，有利於改善廢棄物中污染物質之化學控制方法。因此本研究之主要目的是利用EXAFS及XANES（X-ray absorption near edge structure）解析焚化飛灰經化學穩定化處理 (包括固化、穩定化 (H3PO4)、萃取、電解及高溫燒結融熔)反應中銅之化學結構變化。
利用同步輻射之高強度連續X射線吸收光譜能量探討飛灰中銅之化學結構之變化，發現飛灰中銅主要由Cu(OH)2，CuCl2，CuO和少量 CuS組成，並發現在飛灰驟冷過程中大約82.3%的CuCl2被包夾在鍋爐灰內部，另外大約82%和少於20%的銅分別從集塵灰和鍋爐灰溶出，另外以XPS (X-ray induced photoelectron spectroscopy)分析，可能是大部分銅吸附在集塵灰表面而導致銅相對溶出率較高。
水泥固化過程中銅原子第二層Cu-(O)-Cu鍵距減少約 0.12-0.22 Å，另外固化後飛灰中銅組成為 CuCl2 (0.08-0.11)、Cu2O (0.07-0.09)、Cu(OH)2 (0.31-0.33) 及CuO (0.49-0.52)，藉同步輻射分析可得到固化後CuCl2可能發生氫氧化合反應，另外，Cu2O 和金屬Cu可能發生氧化反應而使得銅溶出減少。
磷酸鹽穩定化作用確認Cu(OH)2 和CuO可能轉化為 Cu3(PO4)(OH)3 而減少銅溶出，同時也發現經穩定後銅原子第二層Cu-(O)-Cu鍵距減少約 0.08 Å，可能導致銅物種之穩定。
XANES數據分析結果顯示紙銅焚化飛灰中銅之物種以 CuCl2（14%）、Cu2O（15%）、Cu(OH)2（27%）及CuO（44%）為主，高溫鍛燒(723~1123 K)造成Cu2O 明顯減少，低沸點物種例如：CuCl2也在高溫(1123 K)揮發。EXAFS顯示飛灰中銅之Cu-O第一層鍵距為1.96 Å，配位數為2.9；Cu-O-Cu(第二層)鍵距2.88 Å，配位數為0.4。高溫鍛燒(1123 K)造成Cu-O第一層鍵距減少0.08 Å；在 923 K鍛燒也造成Cu-O-Cu第二層鍵距減少0.12 Å，但在1123 K高溫燒結可能由於其他原子嵌入使鍵距反而增加0.35 Å。XANES顯示泥渣熔融處理後鋅之主要物種為ZnFe2O4及ZnO，由於表面自由能較低，而可能富集於泥渣表面。高溫鍛燒也可能使低沸點鋅化合物揮發或轉化成高沸點、安定之鋅之氧化物。
利用甲酸、乙酸、丙酸萃取飛灰實驗中，發現乙酸較易萃取CuO，而甲酸、丙酸則對Cu(OH)2有選擇性溶出，Cu(0) 經酸萃後幾乎全被溶出。同時經酸萃後可發現銅原子第二層Cu-(O)-Cu鍵距減少約 0.17-0.23 Å。
電解處理過程發現飛灰中CuO和Cu(OH)2比較容易溶解出而被遷移到陰極，另外比較不同電解質，發現在KNO3 比在KCl 電解液中易被解離出。使用0.1 N KCl電解液，經兩小時的電解處理，發現在離陰極不同位置取樣分析飛灰中分別約19-32%的銅被電解出。使用0.1 N KNO3電解液經一到三小時電解處理，則有約 1-40%的銅被電解析出。
磷酸鹽穩定化處理相對其他穩定重金屬的方法中屬於比較便宜且操作維護簡單。添加磷酸及氫氧化鈣之藥劑成本約2920 NT/ton，若藉由添加底灰稀釋，成本可降至487 NT/ton。

ABSTRACT

Fly ashes discharged from municipal solid waste (MSW) incineration processes generally contain a considerable amount of toxic metals. Copper exerts adverse effects even at concentrations slightly higher than its physiological range. Copper has also been suspected to be carcinogenic and may cause breast and brain cancers. Furthermore, copper may catalyze the formation of dioxins in the MSW incinerator processes.
EXAFS (extended X-ray absorption fine structural) and XANES (X-ray absorption near edge structural) in fact, offer molecular structure data of toxic elements in a very complex matrix that may help the development of effective methods for disposal of hazardous wastes. Because of the dilute nature of toxic metals in the fly ash, literatures are lacking their molecular scale observations. Thus, the main objective of this work was to study the speciation of copper and the possible reaction pathways in the chemical stabilization of fly ashes (solidification, stabilization, extraction, electrokinetics, and sintering/vitrification) by EXAFS and XANES spectroscopies.
The XANES spectra shows that Cu(II) was the main copper species in the fly ashes. Copper species such as Cu(OH)2, CuCl2, CuO, and a very small amount of CuS (3-4%) in fly ashes were determined by semi-quantitative analyses of their edge spectra. During the quench process of the waste heat boiler economizer in the MSW incineration processes, about 82.3% of total CuCl2 were encapsulated in the heat boiler (HB) fly ashes. About 83% and <20% of copper were leached from the electrostatic precipitator (EP) and HB fly ashes, respectively. The relatively high leachavility of copper from the EP fly ash might be due to its high surface concentration of copper that was observed by X-ray photoelectron spectroscopy (XPS).
In the second shells of copper atoms, the bond distance of Cu-(O)-Cu was decreased by 0.12-0.22 Å during solidification, which might cause the stabilization of the CuO species in the solidified fly ash matrix. By the least-square fits of the XANES spectra, fractions of the main copper species in the solidified fly ashes such as CuCl2 (0.08-0.11), Cu2O (0.07-0.09), Cu(OH)2 (0.31-0.33), and CuO (0.49-0.52) were observed. Combined EXAFS and XANES observations suggested that chemical reactions such as hydroxylation of CuCl2 and oxidation of Cu2O and/or metallic Cu might involve in the solidification process, which also led to a significant reduction of the leachability of copper from the solidified fly ashes.
In the phosphate acid stabilization process, after leaching with 0.1 N acetic acid, Cu(OH)2 and CuCO3 might be converted to Cu3(PO4)(OH)3 products. The EXAFS data indicated that the averaged Cu-O bond distance for the untreated fly ash was 1.96 Å with a coordination numbers of 3.0-4.1. However, the Cu-(O)-Cu (2nd shell) bond distance of the fly ash was greater than that of normal CuO by 0.41 Å. In addition, we also found that the Cu-(O)-Cu bond distance of copper (2nd shell) was decreased by 0.08 Å in the stabilization process, which might cause a stabilization of the CuO, CuCO3 and Cu(OH)2 species in the fly ash.
During high-temperature thermal treatments, Cu2O in the fly ashes was oxidized to CuO. Fourier transformed EXAFS (extended X-ray absorption fine structural) spectra of the fly ashes showed that the bond distance of Cu-O was 1.96 Å with coordination number (CN) of 2.9. In the second shells, the Cu-O-Cu bond distance was 3.10 Å with a CN of 0.4. Interestingly, the bonding distance of Cu-O-Cu was increased by 0.35 Å due to the insertin of heavy metals during the high temperature thermal treatments. During vitrification treatments, Zn(0) in the fly ashes was also oxidized to Zn(II). The XANES observations suggested that chemical reactions such as decomposition of ZnCO3 and oxidation of ZnCl2 and/or metallic Zn might involve in the vitrification process, which also led to a significant reduction of the leachability of zinc from the vitrified fly ashes.
Studies on speciation of copper in the fly ashes extracted with formic, acetic, and proponic acids (studied by XANES) suggests the select extractions of CuO with acetic acid and Cu(OH)2 with formic and proponic acids. Moreover, the Cu-(O)-Cu (2nd shell) bond distance of the fly ash decreased by 0.17-0.23 Å in the extracted process.
By XANES, we found that the main copper species in the bag-house fly ash were CuCO3 (8%), metallic Cu (6%), CuO (33%), and Cu(OH)2 (53%). It seems that electrokinetic behavior of copper species from fly ash with 0.1 N KCl and KNO3 electrolyte are similar. Fraction of copper species in the fly ash in the 0.1 N KCl electrolyte between electrodes after a two-hour electrokinetic treatments, it looks like that fast removed rate of copper near the cathode. In the electrokinetic treatment process, CuO and Cu(OH)2 in the fly ash were dissolved and migrated to cathode selectivity.
Volume of the solidified fly ashes usually increase considerably, leading to a highly increase of the disposal cost. The cost of optimum dosages for the phosphoric acid stabilization treatment of the Taichung MSW incineration fly ash was about 2920 NT/ton. In addition, the cost could be reduced to 487 NT/ton by simultaneous treatment of bottom and fly ashes. The phosphoric acid stabilization method would be much simpler and less maintenance demanding if compared to the conventional cement solidification processes.

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