土壤中汞分布型態對萃取含汞污染土壤之影響

Effects of mercury speciation on extraction of contaminated soils

吳政杰(Cheng-Chieh Wu)

指導教授 ： 葉桂君 ； 黃文彥

國立屏東科技大學/工學院/環境工程與科學系所/碩士(2016年)

摘要

溶劑萃取法相對於熱脫附法節能及經濟。汞吸附於土壤除了受於陽離子交換容量大小、土壤中有機質的多寡、土壤的pH值高低及土壤氧化還原電位影響，汞的分布型態也是主要影響因子。
本研究所使用土壤取自某受汞污染場址，探討土壤中汞型態分布對於溶劑萃取汞之影響，使用之萃取劑為0.01 M碘化鉀(KI)，且分別在以下5個pH值範圍(pH=0.5~2.77、pH=0.66~3.83、pH=0.76~5.35、pH=1.21~5.80、pH=1.47~6.68)添加2%過氧化氫(氧化還原電位650 mV以上)萃取三次。
結果顯示高濃度汞污染測試土壤(229 mg/kg)在土壤溶液pH=0.5~2.77/0.01 M KI/2%過氧化氫或pH=1.47~6.68/0.01 M KI/2%過氧化氫條件下萃取去除率最高為86%。汞分布主要為離子可交換態為48%，而溶劑萃取對於離子可交換態、碳酸鹽結合態萃取效果最好，在土壤溶液pH=0.5~2.77、pH=0.66~3.83、pH=0.76~5.3三種條件下萃取，去除率皆達90%以上，但若pH再提高，其去除率會隨著pH升高而降低，當土壤pH值小於4及大於7時，亦對汞之有機結合態有良好的萃取效果。

關鍵字

汞 ； 溶劑萃取 ； 酸 ； 碘化鉀 ； 序列萃取 ； 土壤污染

並列摘要

Relative to the thermal desorption, solvent extraction is an energy-conserving and economic technology. The mercury adsorbed on the soil is primarily affected by the cation exchange capacity, organic matter content, pH and oxidation-reduction potential of the soil. The Hg removal could be affected by its species in soils.
In this study, the tested soil was taken from a mercury-contaminated site. The effect of mercury speciation in the soil on the solvent extraction efficiency was investigated. The mercury contaminated soil was extracted by the 0.01 M KI solution three times in five pH ranges (pH=0.5~2.77、pH=0.66~3.83、pH=0.76~5.35、pH=1.21~5.80、pH=1.47~6.68) and the addition of 2% H2O2 (to maintain the redox potential of above 650 mV).
The Hg concentration in the tested soil is high (229 mg/kg). The Hg removal efficiency is 86% by extraction conditions of soil solution at pH=0.5~2.77/0.01 M KI/2% H2O2 or pH=1.47~6.68/0.01 M KI/2% H2O2 conditions extraction,
The mercury speciation in the soil is primarily the ion exchangeable species（48%）. The Hg in ion exchangeable and carbonate-bound species has the best extraction efficiency. The extraction at pH=0.5~2.77,pH=0.66~3.83 and pH=0.76~5.38 are above 90%. However, if the pH is further increased, the removal efficiency will decrease. When the extraction pH is less than 4 and more than 7, the Hg of organic-matter-bound species has a good extraction efficiency.

並列關鍵字

Mercury ； Solvent extraction ； Acid ； KI ； Sequential extraction ； Soil contamination

參考文獻

李欣怡，2012，汞與戴奧辛污染土壤熱脫附處理研究，碩士論文，國立臺北科技大學，環境工程與管理研究所，台北。

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