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

TY - JOUR

T1 - Investigating the use of synthetic humic-like acid as a soil washing treatment for metal contaminated soil

AU - Yang, Ting

AU - Hodson, Mark Edward

N1 - © 2018 Elsevier B.V. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy

PY - 2019/1/10

Y1 - 2019/1/10

N2 - 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.

AB - 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.

KW - METAL

KW - Remediation

KW - soil washing

KW - humic acid

KW - bioavailability

KW - SOIL

UR - http://www.scopus.com/inward/record.url?scp=85050860140&partnerID=8YFLogxK

U2 - 10.1016/j.scitotenv.2018.07.457

DO - 10.1016/j.scitotenv.2018.07.457

M3 - Article

SN - 0048-9697

VL - 647

SP - 290

EP - 300

JO - Science of the Total Environment

JF - Science of the Total Environment

ER -