鉻在土壤環境中之型態轉換及清洗效率之研究

Chromium forms in soil environment and efficiency of decontamination by washing

賴宏賓(Hung-bin lai)

指導教授 ： 程淑芬

朝陽科技大學/理工學院/環境工程與管理系/碩士(2012年)

摘要

由於台灣地區農田遭受重金屬污染情形相當嚴重，其中重金屬鉻相較於其它重金屬對人體造成危害較為大，但在自然界中鉻存在主要又以Cr（III）及Cr（VI）的型態存在，二者毒性差異非常大。在台灣對重金屬鉻在土壤中管制並沒有嚴格區分Cr（III）及Cr（VI），因此本研究希望了解在受鉻污染農田場址中存在鉻形態的差異及利用不同清洗液對不同的型態重金屬鉻的清洗去除效果，以作為土壤污染清洗整治技術之參考。
本研究主要分為四個部分，第一部分探討陰離子Cr（VI）、陽離子Cr（III）型態鉻在不同特性土壤上鍵結型態分佈之差異。第二部分探討Cr（VI）及Cr（III）污染土壤中，鉻之轉換情形。第三部分是污染不同來源及特性的土壤之特性分析及土壤中重金屬鉻鍵結型態之分析。第四部分是利用不同的酸，包括：鹽酸(HCl)、檸檬酸(Citric acid)、混合酸等酸洗劑對各種型態Cr之去除效率。
研究結果顯示土壤經過前處理烘乾或風乾後，重金屬陰離子Cr（VI）部分會轉換還原成Cr（III），而轉換的型態主要以鐵錳氧化態跟有機態為主。現地污染土壤分析結果顯示大部分Cr是以Cr（III）為主，有些農田地可能會受到工廠排放Cr（VI）、Cr（III）的污染，但在長時間在日光曝曬及風乾下，絕大部分都轉換成三價鉻的形態。清洗結果顯示台中市中興污染場址土壤以0.5M檸檬酸清洗鉻效率最好，去除百分比為54.5%，其次為混合酸49.1%，最後為鹽酸44.47%。酸洗去除鉻污染的土壤以可交換態、碳酸鹽態、殘留態去除效率較高。

關鍵字

六價鉻 ； 三價鉻 ； 土壤清洗 ； 鉻污染

並列摘要

Farmlands in Taiwan are seriously polluted by heavy metals, in which, chromium (Cr) is more harmful than the others to human body. Cr exists mainly in the forms of Cr (III) and Cr (VI) in nature, the toxicities of which are significantly different. Cr (III) and Cr (VI) are not differentiated strictly by Taiwan in the regulation of the heavy metal Cr in soil. This study intended to explore the difference of Cr forms in the Cr-polluted farmlands and the removal effects of Cr in different forms cleaned by different cleaning solutions. The results can serve as a reference for the cleaning and treatment technologies of soil pollutions.
This study was divided into four parts: 1) discussion on the distribution difference of the bonding states of Cr in different forms, i.e. anion Cr (VI) and cation Cr (III) in soil with different characteristics; 2) discussion on the transformation of Cr in the soils polluted by Cr (VI) and Cr (III); 3) analysis on the characteristics of the soil with different pollution sources and characteristics, as well as analysis on the bonding states of the heavy metal Cr; 4) removal effects of Cr in different forms cleaned by HCl, citric acid, mixed acid, and other acid pickling agents.
Based on the results, after pretreatment, such as stoving or air drying, part of the heavy metal anion Cr (VI) would transform and reduce into Cr (III) mainly under ferric-manganese oxidation state and organic state. In the currently polluted soil, Cr was mainly in the form of Cr (III), while some farmlands were likely to be polluted by Cr (VI) and Cr (III) discharged from factories. However, under long-term solarization and air drying, most of Cr (VI) and Cr (III) would transform into trivalent Cr. According to the cleaning results, removal effect of Cr in the soil at Zhongxing pollution site in Taichung City by 0.5M citric acid was the best, with a removal rate of 54.5%, followed by mixed acid with a removal rate of 49.1%, and HCl with the poorest removal effect with a rate of 44.47%. Removal efficiency of Cr from Cr-polluted soil by acid pickling was higher under exchangeable state, carbonate state and residual state.

並列關鍵字

Soil washing ； Chromium contamination ； Cr (III) ； Cr (VI)

參考文獻

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