零價鐵去除水中六價鉻之研究

Hexavalent Chromium Removal by Zerovalent Iron

劉景文(Ching-Wen Liu)

指導教授 ： 駱尚廉

國立臺灣大學/工學院/環境工程學研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.00316

摘要

鉻是一般工業上經常使用之原料，故在工業區附近之地下水中，鉻為最常見的污染物之ㄧ。零價鐵已廣泛的被應用於地下水整治復育工作上，近年來，利用零價鐵現地處理鉻污染的潛力也逐漸被重視。由於零價鐵之比表面積以及鈍化膜為影響其去除效率極為重要的因子，而奈米化後的鐵粉既具備較大的比表面積也具備較薄的鈍化膜，故在應用上遠比商用鐵粉更具效率，因此本研究主要在比較J.T.Baker牌商業鐵粉和自製奈米級鐵粉對於六價鉻之去除效果。
商業鐵粉系統中主要在探討共存陰離子(Cl-、 SO42-、 NO3-、 ClO4- 和 PO43-)、初始pH值和溫度對於六價鉻去除效率之影響 ，而在奈米鐵系統中則沒對溫度的影響進行討論。此外，本研究也有探討六價鉻去除反應之動力模式。
研究結果顯示當六價鉻中含有氯離子和硫酸根時能增加商業鐵粉對六價鉻的去除效果，而硝酸根、過氯酸根及磷酸根則會使商業鐵粉去除六價鉻的效果變差。然而在奈米鐵系統中，氯離子、硫酸根、硝酸根及過氯酸根對於六價鉻的去除效果影響較不明顯，但磷酸根卻會使六價鉻的去除效果明顯降低。
每單位重量零價鐵能去除六價鉻的量為奈米鐵大於商業鐵粉，會有這種結果是因為在商業鐵粉去除六價鉻的系統中，鈍化膜的破壞是主要的速率決定步驟，而在奈米鐵去除六價鉻的系統中則否。
六價鉻初始pH值越高時，商業鐵粉和奈米鐵去除六價鉻的能力均都下降。至於反應動力部分，商業鐵粉去除含氯離子之六價鉻溶液時為假一階反應，但奈米鐵去除六價鉻之反應卻為假二階反應。此外，反應系統的溫度提高時，則有利於商業鐵粉去除六價鉻的能力。

關鍵字：六價鉻、商業鐵粉、奈米鐵、pH、反應動力

關鍵字

六價鉻 ； 商業鐵粉 ； 奈米鐵 ； pH ； 反應動力

並列摘要

Chromium is a common pollutant in groundwater in industrial region because it is a raw material which is often used by many industries. Zero valent iron has been widely used in remediation of groundwater pollution. The potential for using zero valent iron to treat chromium pollution in situ has been concerned in recent years. The surface area and the passivity of the passive film on the iron surface are very important factors for chromium removal by zero valent iron. The surface area for nanolized iron is much larger and the passive film for nanolized iron is much thinner than that for commercial powder iron. Therefore, the chromium removal rate in nanolized iron system should be much higher than that in commercial powder iron system. The efficiencies of chromium removal in nanolized iron and commercial powder iron (J. T. Baker) systems were compared in this work.
Three factors, co-existing anions (Cl-, SO42-, NO3-, ClO4- and PO43-), initial pH and temperature affected on chromium removal were investigated in commercial powder iron system. The same factors except the temperature were investigated in nanolized iron system. The kinetics of the chromium removal reaction was also examined in this study.
The results show that the existence of chloride and sulfate ions can increase the rate of chromium removal by zero valent iron in commercial powder iron system. Otherwise existence of the phosphate, perchloride and nitrate ions can reduce the rate of chromium removal by zero valent iron in commercial powder iron system. However, in nanolized iron system, the influences of chloride, sulfate, nitrate and perchloride ions on chromium removal rate were very relatively insignificant. But the existence of phosphate ion can still decrease the chromium removal rate.
The chromium removal per unit weight of iron in nonalized iron system was much larger than that in commercial powder iron system. This phenomenon indicates the destruction of passive film is the rate-determining step for chromium removal by zero valent iron in commercial powder iron system but is not in nonalized iron system.
Both the removal rate of chromium decreased when the initial pH of chromium is higher. As chromium involves chloride, the kinetic of chromium removal by commercial powder iron follows pseudo-first-order reaction. But in the nanolized iron system, the kinetic follows pseudo-second-order. The chromium removal rate increased with the increase of temperature.

Key words: chromium, commercial powder iron, nanolized iron, pH, kinetic

並列關鍵字

chromium ； commercial powder iron ； nanolized iron ； pH ； kinetic

參考文獻

王鉦源，「以化學還原法製備奈米級銀鈀微粉」，國立成功大學化學工程學系碩士論文，台南市（2002）

Langard, S., Chromium. In: metals in the environment, Waldron, H.A., Eds, Academic Press, London, (1980).

行政院勞工委員會勞工安全衛生研究所，勞工鉻暴露生物偵測標準參考方法之建立，1997。 計畫編號：IOSH 85-A308。

Alowitz, M. J. and Scherer, M. M., “Kinetics of nitrate, nitrite, and Cr(VI) reduction by iron metal,” Environ. Sci. Technol., 36, 299-306 (2002).

Barceloux, D.G., “Chromium,” Clinical Toxicology, 37, 173-194(1999).