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| Remediation of Cadmium and Lead Contaminated Farmland Soil by Washing with Combined Organic Acids and FeCl3 |
| Received:September 28, 2014 |
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| KeyWord:organic acid;FeCl3, heavy metal;contaminated soil;soil washing |
| Author Name | Affiliation | E-mail | | LI Yu-jiao | College of Sciences, Nanjing Agricultural University, Nanjing 210095, China | | | WEN Ya | College of Sciences, Nanjing Agricultural University, Nanjing 210095, China | | | GUO Qian-nan | College of Sciences, Nanjing Agricultural University, Nanjing 210095, China | | | ZHU Yuan | College of Sciences, Nanjing Agricultural University, Nanjing 210095, China | | | DONG Chang-xun | College of Sciences, Nanjing Agricultural University, Nanjing 210095, China | dongcx@njau.edu.cn | | HU Peng-jie | Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China | |
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| Abstract: |
| Soil washing is one option to remediate heavy metal contaminated soils. The present study examined the removal efficiency of cadmium(Cd) and lead(Pb) from a farmland soil by batch extraction with mixture of organic acid(citric acid or tartaric acid) and FeCl3. Metal fractions before and after soil washing were also determined. The Cd and Pb removal efficiency from the soil was up to 40.7% and 20.9% for mixture of citric acid(100 mmol·L-1) and FeCl3(20 mmol·L-1), and up to 42.6% and 16.5% for mixture of tartaric acid(100 mmol·L-1) and FeCl3(20 mmol·L-1), respectively. The metal removal efficiency was higher for mixed reagents than single reagent. Increasing pH of washing solution decreased the removal efficiency of heavy metals. The optimum washing conditions were liquid to solid ratio of 5:1, washing time of 24 h and washing cycles of 3. Metal fractionation showed that the removed Cd by organic acids combined with FeCl3 was mainly from exchangeable(77.3%~79.8% decline) and Fe-Mn oxides forms(86.7%~87.0% reduction), while the organic matter bound metals were almost unchanged. The removed Pb came from Fe-Mn oxides(70.0%~70.8% decrease) and organic matter form(58.8%~66.0% drop). After soil washing, however, the exchangeable Pb significantly increased to 24.2%~24.5%, but Cd and Pb in carbonates almost disappeared with residual metal form unchanged. The removal efficiency of Pb in soil could be significantly increased by repeated washing, and up to 47.0%~48.2% of Pb could be extracted after 3 washing cycles. |
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