- 期刊
以Tween系列界面活性劑加強奈米級零價鐵移動性之研究
Mobility Enhancement of Nanoscale Zero-Valent Iron (nZVI) Modified by Tween-Series Surfactants
摘要
本研究以不同分散劑(polyacrylic acid [PAA], Tween 20, Tween 40, Tween 60)在不同劑量下，對奈米級零價鐵(nanoscale zero-valent iron, nZVI)進行改質，加強其移動性。研究過程先以沉降實驗及管柱傳輸實驗，評估奈米級零價鐵改質後之穩定性及傳輸性，再以批次實驗確認改質後奈米級零價鐵對三氯乙烯(trichloroethylene, TCE)之去除能力。以動態光散射量測懸浮液的粒徑分布後，未經分散劑改質過的奈米鐵裸鐵粒徑約為171.00 nm，而經PAA分散後的奈米鐵顆粒在分析中測出2個主要波峰，分別為8.03 nm與169.40 nm；以Tween 20分散的奈米鐵顆粒在檢測中測出4.22 nm、5.63 nm、6.22 nm、24.15 nm、87.76 nm、1,021.00 nm等波峰，顯示經分散劑改質後的奈米鐵顆粒雖分布並不均勻，但粒徑還是比裸鐵小。在懸浮性的方面，PAA不論是在添加濃度為0.5 ~ 5.0% (vol%)均可使奈米鐵顆粒維持穩定懸浮狀態，而以Tween系列界面活性劑分散的奈米鐵懸浮液多在30分鐘至1小時便已完全沉澱，儘管如此，其懸浮效果依舊較未經改質奈米鐵懸浮液僅能維持5 ~ 10分鐘好。管柱實驗結果顯示，以2% (vol%) Tween 20改質後的奈米鐵懸浮液在管柱中的傳輸效果最佳，在穿透過15 cm之石英砂(孔隙率43.90%)管柱後，其滴出液中的奈米鐵濃度仍有原液的80.8%。以裸鐵及不同分散劑改質後之nZVI降解TCE 之實驗結果皆偵測到降解副產物順-1,2-二氯乙烯(cis-1,2-dichloroethylene, cis-DCE)與1,1-二氯乙烯(1,1-dichloroethylene, 1,1-DCE)，證明TCE已成功還原脫氯。實驗結果顯示，以2% (vol%)的分散劑改質後的奈米鐵懸浮液具有較佳的懸浮性且有較佳的傳輸性。由於Tween 20較PAA易被生物分解，故可做為一種環境友善的nZVI的分散劑。
並列摘要
In this study, nanoscale zero-valent iron (nZVI) was modified by different dispersants (Tween 20, Tween 40, Tween 60, and polyacrylic acid [PAA]) to enhance the mobility and stability of nZVI in the subsurface application. Trichloroethylene (TCE) removal by the modified nZVI was then evaluated. The stability and transportability of bare nZVI were improved by studied dispersants. The results of settling and transportation tests showed that the nZVI perform better in suspension and mobility after 2% (vol%) dispersant modification. The particle sizes were 8.03 and 169.40 nm for bare nZVI; 4.22, 5.63, 6.22, 24.15, 87.76 and 1,021.00 nm for Tween 20 modified nZVI. The particle sizes of dispersant modified nZVI were more uniform and smaller. PAA (0.5-5.0% [vol%]) modified nZVI continued to be stable in suspension throughout the experiments. Tween series modified nZVI lasted for 30-60 mins in suspension, while bare nZVI stayed suspension for only 5-10 mins. The results of column test showed that 2% of Tween 20 could be applied for the modification of nZVI. Due mainly to the easier biodegradable feature of Tween 20 than that of PAA, Tween 20 is an environmentally-friendly dispersant that can improve the mobility of nZVI in the subsurface.