一般重金屬污染物較易吸附或鍵結於微細黏土或砏土上，因此尋找有效分離粗細顆粒之方法，應是受重金屬污染土壤管理上之重要研究課題。本研究主要以擦洗技術探討礦漿濃度、擦洗時間、轉速及萃取劑之添加等操作條件對受污染土壤中重金屬分離富集之影響，並藉由連續式萃取試驗及溶出試驗，用以暸解受污染土壤經擦洗程序後，其粗細粒徑間之重金屬結合型態與溶出行為之變化。
從基本特性分析得知受研究對象污染土壤中重金屬Cu、Pb、Zn、Ni、Hg、Cr濃度均超過土壤管制標準值。歸納擦洗試驗結果發現，於礦漿濃度70 %、擦洗時間20分鐘及轉速2000 rpm條件下，為重金屬分離富集之最佳操作條件，即經擦洗處理後粒徑大於45 μm的部份，能將Cu、Pb、Zn、Ni、Hg、Cr分離出來，並將其富集至粒徑小於45 μm的廢污土壤裡，其中重金屬分離效率依序為Cu(78%)> Zn(69%)> Hg(68%)> Pb(58%)> Ni(48%)> Cr(30%)，至於富集效率為Pb(276%)>Zn(257%)>Ni～Cu(218%)> Cr(195%)>Hg(153%)。由後續重金屬鍵結型態分析及溶出試驗得知，擦洗前後重金屬結合型態之差異不大，但影響粗細顆粒重金屬之含量，其中Cu、Pb、Zn、Ni多以Fe/Mn氧化態存在，而Hg及Cr則以殘留態佔大多數；從溶出結果得知，細顆粒於各pH值下之溶出濃度相對較高，由於Pb及Zn屬於兩性金屬，故只在酸、鹼環境下才會溶出，而Cu與Ni於酸性環境時會明顯溶出，應與其多數呈現Fe/Mn氧化態有關，至於在高pH值時，Hg和Cr之溶出現象推測與其多以殘留態存在有關。就廢棄物管制以TCLP溶出濃度得知，本研究之污染土壤無論經擦洗與否均可通過TCLP溶出標準，可視為一般事業廢棄物，但經最適條件擦洗後，其中約40 wt.%可視為具環境相容性之土壤，達到廢棄物減量之成效。

The fine fraction of contaminated soil particles (clay and silt) tends to concentrate with heavy metals, therefore, it is important to find effective ways of separation between coarse and fine particles on pollution control of heavy- metals contaminated soils. In this study, an attrition scrubber was performed to investigate the influence of scrubbing conditions, including slurry concentration, scrubbing time, impeller speed and chemical reagents, on separation or enrichment of heavy metals in heavy metal-contaminated soils. In addition, through sequential extraction experiments and leaching tests, their chemical characteristics including fractionation pattern of heavy metals and leaching behavior of contaminated soil before and after scrubbing were compared.
From chemical characterization, the soil used was contaminated with Cu, Pb, Zn, Ni, Hg and Cr and their concentrations exceeded the regulatory threshold established by the Environmental Protection Agency of Taiwan (EPA, R.O.C.). The appropriate condition for separating Cu, Pb, Zn, Ni, Hg and Cr from the metal-contaminated soil or concentrating them into a particular soil fraction (<45 μm) was at 70 % of solid slurry, scrubbing time of 20 minutes and impeller speed of 2000 rpm. In this condition, the separation efficiency of heavy metals followed the order : Cu (78%) > Zn(69%) > Hg(68%) > Pb(58%) > Ni(48%) > Cr(30%), and the enrichment efficiency of heavy metals followed the order : Pb(276%) > Zn(257%) > Ni～Cu(218%) > Cr(195%) > Hg(153%).
According to the sequential extractions and leaching tests, the difference in fractionation pattern of heavy metals were not significant but changed of heavy metals contents in coarse and fine particles was observed after scrubbing. Cu, Pb, Zn and Ni existed as the forms of Fe/Mn-oxide but residual bounding for Hg and Cr was shown. The results of leaching tests indicated the leaching concentrations of heavy metals from fine particles were higher over a wide pH range. It was because Pb and Zn were gender metals, their leaching concentrations could be measured at high and low pH. While the leaching of Cu and Ni was obvious under acidic condition, this may cause by the bonding of both Cu and Ni were in the form of Fe/Mn oxide. In addition, the leaching behavior of Hg and Cr at high pH were presumably related to the forms of residual bounding.
From the view of the regulatory threshold of hazardous industrial waste (TCLP), the metal-contaminated soil fulfill the regulatory threshold before and after scrubbing, therefore, they can be regarded as ordinary industrial waste. However scrubbing with appropriate conditions, 40 wt.% of soil may be reuesd in environment and achieved the aim of waste reduction.

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