擦洗技術應用於受砷污染土壤整治之研究

A Study on Remediation of Arsenic-Contaminated Soil by Attrition Scrubbing

李方利(Fang-Li Lee)

指導教授 ： 柯明賢

國立臺北科技大學/工程學院/材料及資源工程系研究所/碩士(2012年)

https://doi.org/10.6841/NTUT.2012.00114

摘要

由受重金屬污染土壤特性之調查結果，顯示土壤中重金屬易吸附或鍵結於黏土或砏土等微細顆粒上，利用擦洗（Attrition scrubbing）程序進行受重金屬污染土壤之整治上，應可藉由土壤顆粒間的表面磨擦及相互撞擊作用將附著於粗顆粒表面的含重金屬之細微顆粒加以脫除分離，而有助於提升後續整治處理程序重金屬之分離與富集效率。本研究係以擦洗結合化學萃取等程序探討對受砷污染土壤之整治效率，並進一步探討擦洗時間、漿體濃度、pH值及酸萃取劑等物理或化學操作條件對整治效率之影響，並藉由連續式萃取試驗以暸解受砷污染土壤於擦洗程序前後其粗細顆粒間各種砷結合型態之變化。
由受砷污染土壤基本特性分析，顯示本研究受砷污染土壤樣本屬於粗質地的「壤質砂土」，其砷含量平均濃度超過土壤管制標準值7倍之多，另由SEM顯微結構觀察可以發現其粗顆粒土壤表面附著大量的極細顆粒污染物。此外，本研究選擇以XRF進行受砷污染土壤中砷濃度分析之探討，以取代傳統實驗室酸消化（AA）分析，由分析結果可以發現二者對於砷分析濃度間具有高度相關性，顯示XRF可作為本研究試驗樣本中砷濃度分析之儀器。
由研究結果可以發現，單純以擦洗時間即將體濃度等物理操作參數進行擦洗時，受砷污染土壤在漿體濃度70 %、擦洗時間20 min進行擦洗程序時，有較佳的砷濃縮富集效率，粗粒度砷濃度去除率達32 %。而在擦洗程序結合化學性酸萃取下，在漿體濃度70 %、擦洗時間20 min及添加10 % 磷酸時為最適操作參數，估計約有70 %的土壤砷平均濃度符合管制標準而得以進行回收利用。另外，由擦洗前後各粒度砷結合型態分析結果顯示，擦洗程序對於各粒度土壤中砷的結合型態變化影響並不明顯，但是卻對粗細顆粒土壤中砷的含量有顯著影響。綜合以上研究結果可知，利用擦洗程序作為受砷污染土壤之前處理具有可行性，可有效提升細顆粒土壤中砷之富集效果而有助於後續土壤分級處理之分離效率。

關鍵字

擦洗 ； 受砷污染土壤 ； 分離 ； 富集 ； XRF

並列摘要

In previous studies, heavy metals have been proven to be easily absorbed or bound in the surface of particle of fine soil, like clay or silt. The attrition scrubbing technique applied to treat heavy metals contaminated soil, because of fine particles with contaminant separated from clean coarse particles during attrition scrubbing process to enhance the efficiency of separation and enrichment of heavy metals contaminant. In this study, the treatment efficiency of arsenic-contaminated soil by attrition scrubbing with chemical extraction processes and scrubbing time, slurry concentration, pH value was studied. The comparisons of particle distribution and chemical structure of arsenic before and after attrition scrubbing treatment were further discussed by the sequential extraction procedure.
From the analysis of soil characteristics, the results show that the average concentration of arsenic-contaminated soil is seven times more than control standard of soil pollution in Taiwan. The particle size of soil in this study belongs to the coarse texture of "loamy sand". A large quantity of finer particles with pollutants is attached to the coarse surface of soil particles by SEM observation of surface micro-structure. In addition, the analysis results of XRF and traditional acid digestion analysis for arsenic concentration indicate that it has a high degree of correlation between the analysis of XRF and traditional acid digestion. It implies that XRF instrument could be used for analyzing arsenic concentration of soil.
The results show that the optimum physical operation parameters are controlled on slurry concentration 70 % and attrition scrubbing time 20 min, the 32 % of arsenic in coarse soil particles could be removed. The attrition scrubbing combined with 10% phosphoric acid solution to enable 70 % of arsenic-contaminated soil for arsenic concentration to be under control standard of soil pollution. It is obvious that the finer soil particle is, and the higher arsenic concentration is. Based on the above results, it is feasible that the attrition scrubbing is used for pretreating arsenic-contaminated soil to concentrate arsenic contents on finer particles.

並列關鍵字

Attrition scrubbing ； Arsenic-Contaminated soil ； separation ； enrichment ； XRF

參考文獻

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