镧改性生物炭在砂柱中单独运移及与 Cr （Ⅵ）共运移

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 co-transport 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.