本研究分為兩部分,第一部分以現地受重金屬銅、鉻及鎳污染土壤進行管柱淋洗實驗,探討鹽酸、檸檬酸及混合酸等不同濃度萃取劑,對土壤中各種型態重金屬之清洗效率;第二部探討陽離子型態三價鉻以及陰離子型態六價鉻在土壤中分佈型態差異;並探討pH對各種型態鉻清洗效率之影響,實驗分別以氯化鉻及重鉻酸鉀代表陽離子型三價鉻以及陰離子型六價鉻,進行土壤污染吸附實驗,並以不同pH之0.1 M檸檬酸在不同清洗時間下探討各種型態重金屬鉻之清洗去除效率。 第一部分研究結果顯示,對於重金屬銅在土壤中主要鐵錳氧化態含量最多,去除效率以0.5 M檸檬酸及0.5 M鹽酸較佳;重金屬鉻以鐵錳氧化態及有機態為最多,去除效率以混合酸較佳;重金屬鎳以鐵錳氧化態含量最多,去除效率以混合酸去除效率較佳。 第二部分研究結果顯示,氯化鉻以及重鉻酸鉀在土壤中之分布都是以鐵錳氧化物鍵結型態為最多,在型態分佈上,氯化鉻以及重鉻酸鉀並沒有顯著的差異。以0.1 M檸檬酸清洗結果顯示氯化鉻的去除效率呈現pH越低去除效率越佳的趨勢;而重鉻酸鉀,則以pH 6之去除效率最佳。以0.1 M檸檬酸清洗三價鉻之清洗所需時間較長,約需48小時以上。
The research has two part in the first part we sample soils contaminated with copper, chromium and nickel and perform soil column leaching tests using hydrochloric acid, citric acid and mix acid to determine the removal efficiency for different forms of heavy metals. The second part is to estimate the cation Cr(III) and anion Cr(VI) distribution in the samples and to determine the pH effects on the acid washing efficiency of these Cr fractions. The experiment with CrCl3 is representative of cation Cr(III) and K2Cr2O7 is representative of anion Cr(VI) in contaminated soil adsorption test and we analyzed the the cleaning efficiencies by Cr forms and by time using 0.1M hydrochloric acid and citric acid. The first part of the study has shown copper in the soil is mainly Fe-Mn oxide-bound and 0.5 M hydrochloric acid and 0.5 M citric acid have better removal efficiency. Chromium is mostly Fe/Mn oxide-bound and organic-bound and the mixed acid is most effective in removal. Nickel is primanily Fe/Mn oxide-bound and the highest removal efficiency is observed using mixed acid solution . The second part of the study showed that CrCl3 and K2Cr2O7 are very similar fractional distribution in the soil and dominated by Fe/Mn oxide-bound. The removal efficiency of CrCl3 with 0.1 M hydrochloric acid appears to correlate negatively with pH values. where as pH 6 is the to best remove K2Cr2O7. The wash solution of 0.1 M citric acid to clean Cr(III) requires time, about 48 hours or longer.