以零價鐵粉還原處理水中硝酸鹽時鐵粉酸洗前處理及起始pH值的影響

Effects of Acid-Prewashing and Initial Solution pH on the Removal of Nitrate by Zero-Valent Iron

本研究的目的在於了解酸洗前處理零價鐵粉對還原處理硝酸鹽的影響，並探討以不同酸劑包括硫酸、鹽酸和醋酸來調整反應起始pH值時，對硝酸鹽被還原之影響。一般商用的鐵粉由於與空氣長時間的接觸，使得表面附著一層氧化鐵鈍化膜，這一層膜會降低零價鐵的活性面積，影響去除硝酸鹽氮的效果。結果發現利用1N的硫酸將鐵粉酸洗時，可以增加硝酸鹽氮的去除效果。而在分別添加硫酸、鹽酸和醋酸調整溶液起始pH值時發現，添加酸洗過的鐵粉，並以鹽酸調整溶液，而且起始pH值為2的條件下，硝酸鹽的去除效果最佳。而在動力學表現上，在起始pH值為2的條件下，用鹽酸調整pH值時的反應速率常數最大；而在起始pH值為3並且添加經過酸洗的零價鐵粉之條件，以醋酸調整pH值時的反應速率常數最大。

The aim of this study is to explore the effect of both acid prewashing of zero-valent iron and initial solution pH adjusted by various acid reagents such as sulfuric acid, hydrochloric acid and acetic acid on the reduction of nitrate. The oxide layers on the iron particles formed by reacting with oxygen, decrease the active area of zero-valent iron and then retard the removal of nitrate. Results indicate that the removal of nitrate could be enhanced by zero-valent iron acid-prewashed with 1N H2SO4. The best removal of nitrate could be obtained under the operational condition of using acid-prewasded iron and initial solution pH adjusted to 2 by using hydrochloric acid. Under the condition of initial pH=2, the observed reaction rate constant of the test adjusted by hydrochloric acid was the largest whereas the observed reaction rate constant was the largest under the condition of initial pH=3 adjusted by acetic acid and dosing with acd-prewashed iron.