沉積物重金屬特性驗證及洗淨再利用探討

Separation,Characterization of Heavy Metals and the Potential Uses of Harbor Sediments

李政諺(Chang-Yan Lee)

指導教授 ： 張益國

中臺科技大學/健康科學院/安全與防災科技研究所/碩士(2012年)

摘要

本研究應用多種溶出試驗，包括pH對初始酸鹼添加之溶出影響等溶出行為試驗(pH-dependent test)、管柱試驗(Percolation test)驗證沉積物重金屬溶出特性，研判重金屬溶出或穩定之可能機制。再以重金屬於pH依存度之溶出行為為基礎，酸洗及萃洗濃集沉積物中重金屬，並對經/未經酸、萃洗之沉積物進行長期溶出特性驗證。結果顯示由微波消化金屬總量分析結果可得知，底泥有害重金屬管制標準中Zn、Cu、Ni、Pb、Cr皆超果標準，其中以Zn、Cu為沉積物含量最高之重金屬。酸洗以HCl、H2SO4、HNO3三種試劑，分別利用0.1 N、1 N進行試驗，其中HCl為1 N時移除效果最佳，對重金屬移除優劣依序為Zn 84% > Ni 72% > Pb 57% > Cu 45% > Cr 43%。螯合萃洗以EDTA、Citric Acid(檸檬酸)兩種試劑，分別利用0.01 M、0.1 M進行試驗，其中以Citric Acid效果為最佳，對重金屬捕集優劣依序為Zn 78% > Ni 48% > Cr 28% > Pb 20% > Cu 2%。
雖酸/萃洗可以有效移除重金屬，但再次經過長期溶出試驗證明，也增加了其殘存之重金屬移動性，使得更容易溶出。最後，探討利用添加不同比例之土地改良劑及水泥，與沉積物結合為試塊狀體，評估其資材化處理可行性。結果發現，其28天抗壓強度最高比例可達375 kg/cm2強度水準，且其資材化塊材經過長期溶出試驗證明其重金屬幾乎不溶出，顯示其具有重金屬長期穩定性。未來應可考慮將沉積物與土地改良劑或水泥混拌後製成資材化塊材，可進行工程上的運用。

關鍵字

沉積物 ； 溶出試驗 ； 酸/萃洗 ； 資材化評估

並列摘要

Contaminated sediments in the harbors remain being a significant issue during dredging operations. Numerous methods have been suggested in recent years for remove, treating and beneficial uses of harbor sediments. In this research, the basic characteristics and the geochemistry of metals in the sediments were studied, and which were subjected to pH‐dependent leaching test, percolation test and column test. The results of experimental leaching tests of harbor sediments are compared with computer calculations. This computer program allows to predict the metal concentrations and the pH of leaching solution at equilibrium, along with the minerals that precipitate and the organic characteristics react with the metal ions forming into stable organic metal compounds.
The result of laboratory research showed that the content of heavy metals contaminants can not meet the Sediment quality standards requirements, thus further treatment such as chemical washing and stabilization/modification are needed before deposition and recycling. Results from the chemical washing (extraction) technique showed that under 0.1M Citric Acid and 1 N HCl as reagents with a sediment/reagent ratio of 1/10, contact time of 60 minutes, the Cu removal efficiency was 2% and 45%, respectively; the Zn removal efficiency was 78% and 84%, respectively; the Ni removal efficiency was 48% and 72%, respectively; the Pb removal efficiency was 20% and 57%, respectively; the Cr removal efficiency was 28% and 43%, respectively; Besides that, stabilization/modification processes (adding with soil amelioration products) can make the heavy metal containing sediment to be low-matrix leach ability and which might be reused as construction material. Thus, this research projects might provide a basic understanding, and the statistic correlation among the sediment characteristics, metal concentration and the possible controlling factors.

並列關鍵字

Contaminated Sediments ； Chemical washing ； Leaching test

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