Abstract：
Nanoscale zerovalent iron synthesized using borohydride (B-NZVI) has been widely applied in environmental remediation in recent decades. However, the contribution of boron in enhancing the inherent reactivity of B-NZVI and its effectiveness in removing hexavalent chromium [Cr(VI)] have not been well recognized and quantified. To the best of our knowledge, herein, a core-shell structure of B-NZVI featuring an Fe-B alloy shell beneath the iron oxide shell is demonstrated for the first time. Alloyed boron can reduce H+, contributing to more than 35.6% of H2 generation during acid digestion of B-NZVIs. In addition, alloyed B provides electrons for Fe3+ reduction during Cr(VI) removal, preventing in situ passivation of the reactive particle surface. Meanwhile, the amorphous oxide shell of B-NZVI exhibits an increased defect density, promoting the release of Fe2+ outside the shell to reduce Cr(VI), forming layer-structured precipitates and intense Fe-O bonds. Consequently, the surface-area-normalized capacity and surface reaction rate of B-NZVI are 6.5 and 6.9 times higher than those of crystalline NZVI, respectively. This study reveals the importance of alloyed B in Cr(VI) removal using B-NZVI and presents a comprehensive approach for investigating electron pathways and mechanisms involved in B-NZVIs for contaminant removal.
摘要：
近几十年来,利用硼氢化物(B-NZVI)合成的纳米零价铁被广泛应用于环境修复。然而,硼在增强B-NZVI的固有反应性方面的贡献及其在去除六价铬[Cr（VI）]方面的有效性尚未得到很好的认识和量化。据我们所知,在这里，首次证明了B-NZVI的核-壳结构，其特征是氧化铁壳下方的Fe-B合金壳。合金硼可以降低H+，在B-NZVIs的酸消化过程中产生超过35.6%的H2。此外,合金B在Cr（VI）去除过程中为Fe3还原提供电子，防止反应性颗粒表面的原位钝化。同时,B-NZVI的无定形氧化物壳表现出增加的缺陷密度，促进壳外Fe2+的释放以减少Cr（VI），形成层状结构的沉淀物和强烈的Fe-O键。因此,B-NZVI的表面积归一化容量和表面反应速率比NZVI晶体高6.5和6.9倍，分别。这项研究揭示了合金B在使用B-NZVI去除Cr（VI）中的重要性，并提出了一种全面的方法来研究B-NZVI去除污染物所涉及的电子途径和机制。
