Mackinawite (FeS), an effective reagent for treating inorganic and organic contaminants, is generally produced as nanoparticles. Since these nanoparticles tend to aggregate to decrease permeability in aquifers and even cause pore clogging, it is often necessary to modify them into such forms to be adequate for preamble reactive barrier (PRB) applications. To this end, this study aimed to produce granular FeS (GFS) from its nanoparticulate precursor using a freeze and thaw method, by which the nanoparticle suspensions were subjected to freezing and then thawing. According to X-ray diffraction, the crystallinity of the resultant GFS was not changed noticeably. By an environmental scanning electron microscope (ESEM), the size of the resultant GFS particles was affected by the type and concentration of electrolytes (e.g., Na₂SO₄, NaCl, and CaCl₂). While the particle size generally increased in the order of Na₂SO₄ ≪ NaCl ≈ CaCl₂, it decreased with the electrolyte concentration. The ESEM images processed with the proposed approach here allowed us to determine the macroporosity of GFS. The GFS prepared using 100 mM Na₂SO₄ solution had the largest population of the pores with ~0.2 µm in diameter. By batch experiments, the As(III) sorption capacity of GFS at neutral to basic pH was comparable to that of the nanoparticulate precursor, suggesting the PRB applicability of GFS to remedy As(III)-contaminated groundwater under anoxic conditions.

Mackinawite（FeS）是用于处理无机和有机污染物的有效试剂，通常以纳米颗粒形式生产。由于这些纳米粒子趋于聚集，从而降低了含水层的渗透性，甚至导致孔隙堵塞，因此通常有必要将其修饰为适合前导反应性反应屏障（PRB）应用的形式。为此，该研究旨在使用冷冻和融化方法从其纳米颗粒前体制备颗粒状FeS（GFS），通过该方法将纳米颗粒悬浮液冷冻然后融化。根据X射线衍射，所得GFS的结晶度没有明显变化。通过环境扫描电子显微镜（ESEM），所得GFS颗粒的尺寸受电解质（例如Na _2）的类型和浓度影响SO ₄，NaCl和CaCl ₂）。而粒径在Na组成的顺序通常增加₂ SO ₄ «氯化钠≈的CaCl ₂，它与电解质浓度降低。用此处提出的方法处理的ESEM图像使我们能够确定GFS的大孔隙度。使用100 mM Na ₂ SO ₄溶液制备的GFS具有最大的孔孔，直径约为0.2 µm。通过分批实验，GFS在中性至碱性pH值下的As（III）吸附能力与纳米颗粒前体相当，这表明GFS的PRB适用于在缺氧条件下修复被As（III）污染的地下水。