都市垃圾焚化底渣之殘餘有機污染物特性研究

Characteristics of Residue Organic Compounds in Municipal Solid Waste Incineration Bottom Ash

林彥妗(Yen-Ching Lin)

指導教授 ： 林正芳

國立臺灣大學/工學院/環境工程學研究所/博士(2011年)

https://doi.org/10.6342/NTU.2011.02920

摘要

都市垃圾經焚化廠處理產生之底渣（bottom ash），除了應用於掩埋場覆土材料之外，燒結、熔融、作為建築、道路鋪設骨材等之再利用方式，亦逐漸受到關注。大部分底渣之回收應用需符合重金屬含量及其環境溶出潛勢的檢驗規定。然而，除了微量重金屬之外，底渣中仍含有部分因焚化處理不完全，於燃燒過程中氧化反應殘留之毒性及臭味有機物。
都市垃圾焚化底渣中殘留之有機碳可區分為元素碳、可萃取之有機碳及非可萃取之有機碳，過去相關研究以水及二氯甲烷萃取底渣之有機碳分別為110–1,670 mg kg-1 及 0–842 mg kg-1 ，顯示底渣中仍有非可萃取之有機碳殘留，因此研究中針對經再利用前處理之都市垃圾焚化底渣，應用超臨界流體萃取（SFE）和半自動索氏萃取（Soxtec extraction）經再利用前處理之都市垃圾焚化底渣，利用氣相層析法（gas chromatography - mass spectrometry, GC-MS）進行底渣中有機組成之質性及量化分析，藉以探討底渣中複雜的有機混合物組成特性，並評估水洗程序作為底渣再利用預處理之成效。
底渣中殘留有機污染物之量化分析主要為酚類化合物、含氯化合物、多環芳香族碳氫化合物及有機酸等，而水洗後水中之有機污染物則應用液相–液相萃取（liquid-liquid extraction, LLE）後以GC-MS分析。底渣經由超臨界流體萃取（SFE）及半自動索氏萃取（Soxtec extraction），以GC-MS定性之結果共分析得149種有機化合物，經水洗程序之底渣則共分析得40種有機化合物。
超臨界二氧化碳萃取利於萃取底渣中之弱極性之芳香族化合物和芳香胺，且不與萃取標的化合物產生化學反應，半自動索氏萃取（丙酮：正己烷，1：1 v/v）則利於萃取底渣中之極性與弱極性脂肪族化合物和芳香族化合物，故應用超臨界二氧化碳萃取及半自動索氏對於底渣之有機特性分析而言，具有相互輔助之功能。
底渣水洗後之TOC由0.7–4.1% （Carbon）減至小於 1.9% （Carbon），即底渣中平均約有68% 之含碳有機物能以水洗方式去除。水洗前底渣中萃取出之有機成分種類以脂肪族化合物及芳香族（芳香環）化合物為主，水洗後各類化合物分佈均顯著減少，尤以脂肪族胺類及芳香族胺類幾乎未萃出，芳香族（芳香環）化合物亦顯著減少。
比較底渣中萃出之各類有機化合物含有特殊之致臭或毒性結構組成，可歸納4 種具環境危害成份之有機化合物，包含：吡啶（pyridine）、喹啉衍生物（quinoline derivatives）、含氯有機化合物（chloro-organic）、氰基有機化合物（cyano-organic）。水洗後之底渣中此 4 類有機化合物顯著減少，故底渣經水洗過程可將其中未燃燒完全之有機致臭化合物及大部份的胺類化合物、部分芳香族（芳香環）化合物及脂肪族化合物去除。故水洗為一簡易且有利於去除再生都市垃圾焚化底渣中有機殘留物，此應用將可降低都市垃圾焚化底渣再利用對環境的風險。

關鍵字

底渣 ； 水洗 ； 殘留有機物 ； 超臨界二氧化碳萃取 ； 索氏萃取 ； 臭味

並列摘要

Although heavy metals in bottom ash have been a primary issue in resource recovery of municipal solid waste incinerator residues in past decades, less studied are potentially toxic and odorous organic fractions that exist as they have not been completely oxidized during the mass burn process.
The organic carbon residues contained in municipal solid waste incineration bottom ash (MSWIBA) can be categorized into elemental carbon, extractable organic carbon and non-extractable organic carbon. The data showed the fraction of extractable organic carbon by water and dichloromethane are 110–1,670 mg kg-1 and 0–842 mg kg-1, respectively. The non-extractable organic carbon is in the range of several grams per kg of bottom ash, indicating most of the organic carbon residues are not easily water extractable. Therefore, there is a need to reveal the spectrum of the organic carbon residues in MSWIBA and to evaluate the effectiveness of using water washing as a pre-treatment process for reducing the environmental risk of the organic residues when recycling MSWIBA. In this work, two extraction techniques, soxtec extraction (SE) and supercritical fluid extraction (SFE), were employed for the full spectrum of the organic carbon residues in MSWIBA before and after pre-treatment with water washing. Although organic compounds in raw bottom ash of different seasons extracted by SE and SFE showed obvious variability, organic compounds in water-washed bottom ash of different seasons extracted by SE and SFE showed noticeable stability.
The major organic compounds such as phenols, chloro-organics and carboxylic acids in the weathered and water-washed bottom ash were quantitatively determined by GC-MS and those in washing water were determined with GC-MS after liquid-liquid extraction. For all the bottom ash samples, a total of 149 compounds were foun from weathered bottom ash and a total of 40 compounds were found from water-washed bottom ash. Organic compounds in water-washed bottom ash such as aliphatics, aliphatic amines, aromatic amines and aromatic compounds extracted by SFE and SE from different incinerators distributed over similar frequency and it was much lower than organic compounds in weathered bottom ash.
The results of quantification demonstrated that fewer organic compounds were detected in water-washed bottom ash extraction with SFE and only one chloro-organic was identified from water-washed bottom ash by SE. It indicates the effectiveness of water washing as pretreatment for organics such as several phthalates (e.g., phthalic acid isobutyl tridec-2-yn-1-yl ester, dibutyl phthalate and 2-butoxyethyl butyl benzene-1,2-dicarboxylate), organic phosphates (e.g., octicizer and phosphoric acid isodecyl diphenyl ester), aromatic amines (e.g. 1-nitro-9,10- dioxo-9,10-dihydro-anthracene-2-carboxylic acid diethylamide and 3-bromo-N- (4-bromo-2-chlorophenyl)-propanamide) and aromatic compounds (other than amines) (e.g. 7-chloro-4-methoxy-3-methyl- quinoline and 2,3-dihydro-N- hydroxy-4-methoxy-3,3-dimethyl indole-2-one). The results here suggest that washing with water can be an effective pre- treatment step for removing odour-causing and environmental concerned organics.

並列關鍵字

Bottom ash ； Water washings ； Organic residue ； Supercritical fluid extraction ； Soxtec extraction ； Odour

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