穆云松等：Cysteine-enhanced reductive degradation of nitrobenzene using nano-sized zero-valent iron by accelerated electron transfer.
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）是一種脂肪族氨基酸，廣泛存在于動植物細胞中。目前尚未見關于CYS對納米級零價鐵（NZVI）降解污染物的影響報道。我們的研究發現CYS的引入將顯著提高nZVI的反應活性，其對硝基苯的降解效率提高了約30％，反應速率常數提高了9倍。NB的降解率與CYS濃度在0至10 mM之間呈正相關。CYS的引入同時增強了nZVI系統中Fe（III）和Fe（II）的釋放。單獨的CYS或Fe（II）對硝基苯的降解實驗表明，CYS的直接還原作用不是提高NB去除效率的主要因素。此外，CYS的濃度會隨著反應時間而降低，伴隨著胱氨酸（CY，CYS的氧化態）的產生，兩者的濃度最終都趨于穩定。CY的引入同樣可以增強nZVI對NB的降解效率，并且我們還觀察到CYS的再生。這些結果表明，CYS可以充當電子穿梭體，加速nZVI向NB的電子轉移并提高NB的降解效率。
原載于Journal of Environmental Sciences（2019 Impact Factor = 4.302）