Abstract
In situ stabilization is a remediation technology that reduces the availability of mercury in contaminated soils by adding chemical substances. In this study, thiol-functionalized montmorillonite modified by organic surfactant (Mont-OR-SH) was used to stabilize soils contaminated with different concentrations of mercury. The Mont-OR-SH used in this study was obtained by grafting the thiol group (–SH) to the montmorillonite modified by organic surfactant (Mont-OR). The physicochemical characteristics were analyzed by XRD, FTIR, and SEM, confirming that the Mont was successfully functionalized, while the concentration of mercury was analyzed by the cold-vapor atomic absorption (CVAA) method. Contaminated soils were mixed with Mont-OR and Mont-OR-SH at different dosages. The effect of stabilization time was investigated when the Mont-OR-SH dosages were 7 wt% and 8 wt%, and five different stabilization pH values were used to investigate the influence on stabilization when the stabilizer dosages was 8 wt%. A sequential extraction procedure and a toxicity leaching procedure were used to evaluate remediation performance. The result indicated that the Mont-OR-SH was effective in stabilizing mercury-contaminated soil, and the stabilization capacity was greatly enhanced upon thiol grafting. Stabilization efficiency for both kinds of soil was greater than 90% after stabilizing by Mont-OR-SH. For two kinds of soils, with a stabilization duration of 14 days, the stabilizer dosage was about 8 wt% and the pH of the leaching was 8.0; the stabilization efficiency could reach 91.7% and 96.7% when stabilized by Mont-OR-SH which is higher than 60.4% and 82.4% when stabilized by Mont-OR. For two kinds of soils, the contents of neutral fraction were reduced and changed to acid fraction, base fraction, sulfide fraction, and residual fraction. Stabilization capacity of Mont-OR was greatly enhanced after the thiol group was loaded; the stabilization process using Mont-OR-SH was effective to treat mercury-containing soils.
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