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| Transport of single La-modified biochar in a sand column and its co-transport with Cr(Ⅵ) |
| Received:June 08, 2022 |
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| KeyWord:La-modified biochar;Cr (Ⅵ);quartz sand media;co-transport;retention;soil;groundwater |
| Author Name | Affiliation | E-mail | | GU Xinfeng | School of Environmental Science & Engineering, Nanjing Tech University, Nanjing 211816, China | | | PAN Hui | School of Environmental Science & Engineering, Nanjing Tech University, Nanjing 211816, China | | | ZHANG Lianyi | School of Environmental Science & Engineering, Nanjing Tech University, Nanjing 211816, China | | | DING Zhuhong | School of Environmental Science & Engineering, Nanjing Tech University, Nanjing 211816, China | dzhuhong@njtech.edu.cn |
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| Abstract: |
| In order to investigate the transport of rare earth metal-modified biochar in soil-groundwater, lanthanum, a common rare earth element, was used to prepare modified biochar in this study. The lanthanum-modified biochar was then ball-milled to obtain fine biochar particles(La-BC). The transport and retention of La-BC alone(single-transport), and together with Cr(Ⅵ) (co-transport), in a saturated quartz sand column were studied at different conditions of flow rate, pH, ionic strength, and humic acid concentration. The results showed that the mass recovery of La-BC in the effluent increased from 58.0% to 73.4% in single-transport and ranged from 78.7% to 80.1% in cotransport when flow rate was increased from 1.0 mL · min-1 to 1.5 mL · min-1. The peak relative concentration(Ct/C0) values of La-BC breakthrough curves in single-transport and co-transport increased from 0.66 to 0.93 and from 0.80 to 0.85 when pH increased from 5 to 7. The peak Ct/C0 values of La-BC breakthrough curves were reduced to 0.05 in single-transport when ionic strength increased to 5 mmol·L-1, and to 0.81-0.75 in co-transport. The mass recovery in the effluent was reduced by about 13 percentage points and about 3 percentage points in single-transport and co-transport when humic acid concentration increased from 0 to 10 mg·L-1. Compared with single-transport, the existence of Cr(Ⅵ) in co-transport inhibited transport of La-BC under neutral conditions in a saturated medium and promoted its transport under other experimental conditions. Therefore, appropriately low flow rate, low pH, a certain ionic strength, and humic acid concentration contribute to the retention and stabilization of the modified biochar. |
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