ABSTRACT:

As an aliphatic amino acid, cysteine (CYS) is diffuse in the living cells of plants and animals. However, little is known of its role in the reactivity of nano-sized zero-valent iron (NZVI) in the degradation of pollutants. This study shows that the introduction of CYS to the NZVI system can help improve the efficiency of reduction, with 30% more efficient degradation and a reaction rate constant nine times higher when nitrobenzene (NB) is used as probe compound. The rates of degradation of NB were positively correlated with the range of concentrations of CYS from 0 to 10 mmol/L. The introduction of CYS increased the maximum concentration of Fe(III) by 12 times and that of Fe(II) by four times in this system. A comparison of systems featuring only CYS or Fe(II) showed that the direct reduction of NB was not the main factor influencing its CYS-stimulated removal. The reduction in the concentration of CYS was accompanied by the generation of cystine (CY, the oxidized form of cysteine), and both eventually became stable. The introduction of CY also enhanced NB degradation due to NZVI, accompanied by the regeneration of CYS. This supports the claim that CYS can accelerate electron transfer from NZVI to NB, thus enhancing the efficiency of degradation of NB.

KEYWORDS: Zero-valent iron，Nanoparticles，CYS，Electron shuttle，Reactivity

摘要: 半胱氨酸（CYS）是一种脂肪族氨基酸，广泛存在于动植物细胞中。目前尚未见关于CYS对纳米级零价铁（NZVI）降解污染物的影响报道。我们的研究发现CYS的引入将显著提高nZVI的反应活性，其对硝基苯的降解效率提高了约30％，反应速率常数提高了9倍。NB的降解率与CYS浓度在0至10 mM之间呈正相关。CYS的引入同时增强了nZVI系统中Fe（III）和Fe（II）的释放。单独的CYS或Fe（II）对硝基苯的降解实验表明，CYS的直接还原作用不是提高NB去除效率的主要因素。此外，CYS的浓度会随着反应时间而降低，伴随着胱氨酸（CY，CYS的氧化态）的产生，两者的浓度最终都趋于稳定。CY的引入同样可以增强nZVI对NB的降解效率，并且我们还观察到CYS的再生。这些结果表明，CYS可以充当电子穿梭体，加速nZVI向NB的电子转移并提高NB的降解效率。

关键词: 零价铁，纳米颗粒，CYS，电子穿梭，反应性

原载于Journal of Environmental Sciences（2019 Impact Factor = 4.302）

原文链接： https://www.sciencedirect.com/science/article/pii/S100107422030320X