School of Mechanics and Engineering Science, Shanghai University, 200444, Shanghai, PR China.
Chemosphere. 2022 Nov;307(Pt 2):135902. doi: 10.1016/j.chemosphere.2022.135902. Epub 2022 Aug 7.
This study evaluated the use of a sustainable GFD binder for the stabilization/solidification (S/S) of chromium VI (Cr(VI))-contaminated soil. The GFD binder was composed of ground granulated blast furnace slag (GGBFS), fly ash and desulfurization ash, named after the initials of the three materials. The effects of curing time and binder dosage on soil unconfined compressive strength (UCS), Cr leachability, soil pH, and reduction ratio of Cr (VI) were tested. The immobilization mechanisms of Cr(VI) in contaminated soil were further explored using X-ray diffraction (XRD), scanning electron microscopy (SEM), and sequential extraction procedure (SEP). The results showed that the UCS and pH of the soil increased substantially after the GFD binder was added. After 28 days of curing with a 20% binder dosage, the leached total Cr concentration decreased from 34.4 mg/L in the contaminated soil to 1.44 mg/L in the treated soil, and the leached Cr(VI) concentration decreased from 28.0 mg/L to 0.45 mg/L. A Cr(VI) reduction ratio of 96.2% was achieved, indicating the strong reducibility of GGBFS. XRD revealed that the main hydration products of the GFD binder were hydrated calcium silicate (C-S-H) and ettringite. SEM results showed that the formation of hydration products and Cr-bearing precipitates filled the soil pores, resulting in a dense soil structure. The SEP results demonstrated that the levels of the unstable fraction F1 decreased considerably, and that the levels of the stable fractions F3 and F5 increased after treatment. Encapsulation by C-S-H, reduction by sulfides, adsorption of C-S-H, and precipitation of Cr-bearing hydroxides were the main mechanisms involved in Cr immobilization using the GFD binder.
本研究评估了一种可持续的 GFD 结合剂在稳定/固化（S/S）六价铬（Cr(VI)）污染土壤中的应用。GFD 结合剂由磨细粒化高炉矿渣（GGBFS）、粉煤灰和脱硫灰组成，这三种材料的首字母组合命名了该结合剂。测试了养护时间和结合剂用量对土壤无侧限抗压强度（UCS）、Cr 浸出率、土壤 pH 值和 Cr(VI)还原率的影响。进一步通过 X 射线衍射（XRD）、扫描电子显微镜（SEM）和顺序提取程序（SEP）探究了污染土壤中 Cr(VI)的固定化机制。结果表明，添加 GFD 结合剂后，土壤的 UCS 和 pH 值显著增加。在 20%结合剂用量养护 28 天后，浸出液中总 Cr 浓度从污染土壤中的 34.4 mg/L 降低到处理土壤中的 1.44 mg/L，浸出液中 Cr(VI)浓度从 28.0 mg/L 降低到 0.45 mg/L。实现了 96.2%的 Cr(VI)还原率，表明 GGBFS 具有很强的还原能力。XRD 表明，GFD 结合剂的主要水化产物为水化硅酸钙（C-S-H）和钙矾石。SEM 结果表明，水化产物和含 Cr 沉淀物的形成填充了土壤孔隙，导致土壤结构致密。SEP 结果表明，处理后不稳定组分 F1 的水平显著降低，稳定组分 F3 和 F5 的水平增加。C-S-H 的包裹、硫化物的还原、C-S-H 的吸附和含 Cr 氢氧化物的沉淀是 GFD 结合剂固定 Cr 的主要机制。
