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請使用永久網址來引用或連結此文件:
https://ir.cnu.edu.tw/handle/310902800/6130
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| 標題: | 腐植酸與金屬離子對奈米級與微米級零價金屬處理水中硝酸鹽之影響
Effects of humic acid and metal ions on nitrate reduction by both nanoscale and microscale zero-valent metals |
| 作者: | 陳裕太
Yu-Tai Chen |
| 貢獻者: | 余光昌
嘉南藥理科技大學：環境工程與科學系碩士班 |
| 關鍵字: | 金屬離子
腐植酸
奈米
硝酸鹽
metal ions |
| 日期: | 2005 |
| 上傳時間: | 2008-10-31 16:14:52 (UTC+8) |
| 摘要: | 硝酸鹽為常見的地下水污染物之一，主要經由含氮肥料或農藥的施灑、動物廢棄物以及污水系統而滲入地下水中。硝酸鹽的去除方式大致上可分物理方式、生物方式、化學方式等。物理方式係將硝酸鹽濃縮，並沒有將其去除，而必須再進一步進行處理。而生物處理最大的缺點就是處理時間長，且必須要有較高的技術及昂貴的設備。故比較起來，反應快速又可降解去毒之化學法處理似為不錯的方法。近年來，以零價金屬(zero-valent metals)去氯還原處理含氯有機污染物(如TCE或CCl4)或氧化態無機污染物(如硝酸鹽、六價鉻或砷酸鹽等)之研究甚多，也不失為一種簡單又處理迅速的方法。本研究便是以此法來探討一些影響因子對零價金屬去除水中硝酸鹽之影響。
本研究所使用的鐵粉分別為微米級(商業購得)及奈米級零價鐵(自行合成)，分別探討此兩種鐵粉處理水中硝酸鹽(NO3－)時之效果及動力研究。目前奈米鐵粉於市面上較少販售，因此本研究特以化學還原法合成，並以電子顯微鏡(SEM)觀測其粒徑大小及外觀，以比表面積分析儀(BET)及X光繞射儀(XRD)分別測定其比表面積及成份結構。
本研究以批次實驗分別比較不同鐵粉尺寸(微米級(200mesh)、奈米級)、鐵粉添加劑量、起始pH值、溶液中腐植酸濃度(5mg/L、10mg/L)、額外添加的金屬離子(Fe2+、Ni2+、Cu2+)及劑量(0.1mM、1.0mM)等影響因素對硝酸鹽被零價金屬還原去除之影響，並藉由硝酸鹽與零價金屬之反應動力(reaction kinetics)來推算比較不同影響因素下其反應速率常數(reaction rate constant)及半衰期(half-life time)。
研究結果發現不論是微米級或是奈米級零價鐵，當在低起始pH值時，其對硝酸鹽均有不錯的還原去除效果；而溶液中所添加的三種兩價金屬離子均有助於零價鐵對硝酸鹽的還原效果，其增進的效果係隨著離子添加劑量的增加而增加，其中又以添加Cu2+之效果最好，Fe2+次之，Ni2+最差。此外，如添加腐植酸於溶液中亦會增加零價鐵的還原能力，但是其效果在微米級的金屬中較不顯著。比較此兩種不同尺寸之零價鐵之還原去除效果時發現，奈米零價鐵對硝酸鹽的去除效果遠優於微米級零價鐵。從本研究探討的控制因素中發現，影響微米級零價鐵對硝酸鹽去除效果之主要因素為起始pH值的控制，而鐵粉的添加量則對奈米級零價鐵還原去除硝酸鹽時之影響則相當顯著。
在本研究中除零價鐵外，亦有嘗試利用兩種不同尺寸(微米級(325mesh)、奈米級)之零價鎳處理硝酸鹽，但發現不論微米級或是奈米級之零價鎳金屬，其對硝酸鹽氮之去除均沒有任何效果。
Nitrate is one of the major pollutants in groundwater. Anthropogenic sources such as nitrogen fertilizers, nitrogen pesticides, animal wastes, and septic systems account for most nitrate contamination of groundwater. Removing nitrate from water include physical, biological and chemical technologies. Nitrates can be condensed by using physical technologies, but need a further treatment. The drawbacks of biological technologies to remove nitrates from water are (1) longer reaction time, (2) expensive equipments, (3) well operation skills. However, chemical methods can quickly degrade and reduce pollutants and are frequently used for remediate groundwater. Recent research has demonstrated that many potential uses of zero-valent metals (ZVM) in the remediation of groundwater polluted with organic contaminants (such as TCE, CCl4) or inorganic contaminants (such as nitrates, chromates or arsenates). The aim of this study is to determine the effect of some factors on nitrate reduction by using ZVM.
Microscale (commercial) and nanoscale (self- prepared) ZVM were used in this study. Both were determined with BET, SEM and XRD for comparing their physicochemical properties.
The initial conditions controlled included both particle size and dosage of ZVM, pH, humic acid content and both type and dosage of additional divalent metal ions. The observed reaction rate constant (Kobs) and half-life time (t1/2) were determined by reaction kinetics.
Results show that nitrate removal was fast and efficient in the acidic condition. Additional dosing of divalent metal ions could enhance the nitrate removal, which increased in the order: Ni2+＜Fe2+＜Cu2+. The efficiency of nitrate removal increased with the dosage of divalent metal ions. In presence of humic acid, a commonly natural organic compound, nitrate removal by ZVM could be enhanced, but insignificantly in the reaction with microscale iron.
Nanoscale iron showed higher reducing potential on nitrate than microscale iron whereas both microscale and nanoscale nickel had no effect on the removal of nitrate.
It could be noted that the main controlled factor of the removal of nitrate by microscale iron was initial solution pH whereas the main controlled factor of the removal of nitrate by nanoscale iron was the dosage of iron. |
| 關聯: | 校內外完全公開 |
| 顯示於類別: | [環境工程與科學系(所)] 博碩士論文
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