School of Civil and Environmental Engineering, Nanyang Technological University, Singapore.
School of Civil and Environmental Engineering, Nanyang Technological University, Singapore.
Chemosphere. 2022 Jan;287(Pt 3):132274. doi: 10.1016/j.chemosphere.2021.132274. Epub 2021 Sep 20.
Ladle furnace slag (LFS) is a by-product of the steel industry and is difficult to be reused due to its weak cementitious property, low strength, and potential leaching of heavy metals. The emission of carbon dioxide (CO) is also a concern for the steel industry. Therefore, the aim of this study was to use CO to immobilize heavy metals in LFS and enhance its strength. The LFS specimens were carbonated with different initial water contents, CO pressures, and carbonation periods. The carbonated LFS were then studied by leaching test, unconfined compressive strength (UCS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), fourier transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FESEM) with energy dispersive X-ray spectroscopy (EDX). The results showed that LFS had carbonation reactivity and could sequester CO up to 9.6% of its own mass. The carbonation also effectively reduced the leaching of heavy metals from LFS, especially Pb and Zn. The concentrations of leached Pb and Zn of carbonated LFS were significantly reduced from 2760 and 1460 μg/L to 0.11 and 0.56 μg/L, respectively, being one order of magnitude (Pb) or three orders of magnitude (Zn) lower than limits of inert waste and three drinking water regulations. The strength of the carbonated LFS also remarkably increased and was two orders of magnitude higher than that of the uncarbonated LFS. Following the carbonation, calcium carbonate, nesquehonite, and hydromagnesite were produced; these carbonates filled pores and bound LFS particles, which enhanced the strength of LFS.
钢渣是钢铁行业的副产品，由于其胶凝性能弱、强度低以及重金属潜在浸出等问题，难以被再利用。二氧化碳（CO）的排放也是钢铁行业关注的问题。因此，本研究旨在利用 CO 固定钢渣中的重金属并提高其强度。通过不同的初始水含量、CO 压力和碳酸化时间对钢渣试件进行碳酸化。通过浸出试验、无侧限抗压强度（UCS）、X 射线衍射（XRD）、热重分析（TGA）、傅里叶变换红外光谱（FTIR）和场发射扫描电子显微镜（FESEM）结合能谱（EDX）对碳酸化钢渣进行研究。结果表明，钢渣具有碳酸化反应性，可以封存自身质量 9.6%的 CO。碳酸化还能有效降低钢渣中重金属的浸出，特别是 Pb 和 Zn。碳酸化钢渣中浸出 Pb 和 Zn 的浓度分别从 2760 和 1460μg/L 显著降低至 0.11 和 0.56μg/L，分别降低了一个数量级（Pb）或三个数量级（Zn），低于惰性废物和三个饮用水规定的限值。碳酸化钢渣的强度也显著提高，比未碳酸化钢渣高两个数量级。碳酸化后生成了碳酸钙、水菱镁矿和水镁石；这些碳酸盐填充了孔隙并结合了钢渣颗粒，从而提高了钢渣的强度。
