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Investigating the use of synthetic humic-like acid as a soil washing treatment for metal contaminated soil

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JournalScience of the Total Environment
DateAccepted/In press - 30 Jul 2018
DateE-pub ahead of print - 1 Aug 2018
DatePublished (current) - 10 Jan 2019
Volume647
Number of pages2
Pages (from-to)290-300
Early online date1/08/18
Original languageEnglish

Abstract

Humic acid can effectively bind several metals and is regarded as a promising soil washing agent. Previous studies indicate that carboxylic groups dominate metal binding to humic acid. In this study, a synthetic humic-like acid (SHLA) with high COOH content (5.03 mmol/g) was used as a washing agent to remove metals (Cu, Zn, Ni, Pb, As) from two contaminated agricultural soils (Soil 1 (pH: 6.17±0.11; organic carbon: 5.91±0.40%; Cu: 302.86±3.97 mg/kg; Zn: 700.45±14.30 mg/kg; Pb 323.56±4.84 mg/kg; Ni: 140.16±1.59 mg/kg) and Soil 2 (pH: 9.83±0.01; organic carbon: 2.52%±0.25%; Cu: 242.81±10.66 mg/kg; Zn: 841.00±22.31 mg/kg, Pb 451.21±1,92 mg/kg, As: 242.23±5.24 mg/kg)). The effects of solution pH (4 to 11), liquid/solid ratio (L/S ratio, 5:1 (mL:g) to 80:1 (mL:g)), SHLA concentration (100 mg/L to 2000 mg/L), and contact time (0 to 1440 min) on % metal removal were investigated and optimum conditions identified: pH of 9, L/S ratio of 1:80, SHLA concentration of 1500 mg/L at 25 ℃ for 4 h. Under optimum conditions, a single washing removed 45.2% of Cu, 34.6% of Zn. 42.2% of Ni and 15.6 % of Pb from Soil 1, and 30.6% of Cu, 28.1% of Zn. 14.6% of As and 18.1% of Pb from Soil 2. A modified BCR extraction of the two soils before and after washing indicated that the SHLA mainly removed metals in the exchangeable and acid soluble fraction and reducible fraction, which could effectively reduce bioavailability and environmental risk of metals. On a molar basis, SHLA was a more effective washing agent than commercial humic acid, Na2EDTA, citric acid and tartaric acid. Overall, SHLA shows great potential for use as a soil washing agent.

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© 2018 Elsevier B.V. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy

    Research areas

  • METAL, Remediation, soil washing, humic acid, bioavailability, SOIL

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