EPS adsorption to goethite: Molecular level adsorption mechanisms using 2D correlation spectroscopy
EPS adsorption to goethite: Molecular level adsorption mechanisms using 2D correlation spectroscopy
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DOI：
10.1016/j.chemgeo.2018.07.028
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发表时间：
2018-09
期刊：
影响因子：
3.9
通讯作者：
P. Cai;Di Lin;C. Peacock;W. Peng;Qiaoyun Huang
中科院分区：
文献类型：
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作者：
P. Cai;Di Lin;C. Peacock;W. Peng;Qiaoyun Huang
胞外聚合物(EPS)在土壤矿物上的吸附是了解细菌在矿物表面的附着以及营养和污染物的环境循环的重要过程。为了从分子水平上阐明EPS的吸附机理和过程，利用二维傅立叶变换红外光谱(FTIR)结合C1S近边X射线吸收精细结构谱(NEXAFS)研究了EPS与针铁矿的相互作用机理。结果表明，EPS的酰胺官能团对其在针铁矿上的吸附起着重要作用，EPS-蛋白质在针铁矿上的吸附是电解质浓度的函数，且在较高的电解质浓度下吸附增加。结果还表明，EPS官能团与针铁矿相互作用和结合的顺序与电解液浓度有关，在低电解液浓度下，羧基和磷酰基首先被吸附，而在较高电解液浓度下，酰胺基团首先被吸附。在吸附过程结束时(~300min)对酰胺I带的解卷积和曲线拟合表明，蛋白质的二级结构从无规卷曲构象转变为聚集链、α-螺旋和转角。这种转化导致EPS-蛋白质的吸附增加，并解释了EPS在针铁矿表面的总吸附随着电解液浓度的增加而增加。此外，EPS对羧基官能团的吸附随着电解液浓度的增加而降低，这可能是由于随着电解液浓度的增加，针铁矿表面电荷被更有效地屏蔽所致。ATR-FTIR和2D-CoS的综合结果使我们能够在分子水平上构建EPS-针铁矿相互作用过程的全面概述，这可以用来提高我们对自然环境中EPS-矿物相互作用的理解。这些结果也为更好地了解土壤和沉积物矿物上细菌生物膜的形成提供了基础信息，并有助于研究自然环境和污染环境中营养物质和污染物与生物膜活性成分之间的相互作用。
The adsorption of extracellular polymeric substances (EPS) onto soil minerals is an important process for understanding bacterial adhesion to mineral surfaces and environmental cycling of nutrients and contaminants. To clarify the molecular level mechanisms and processes of EPS adsorption, the interaction mechanisms between EPS and goethite was explored using two-dimensional (2D) Fourier transformation infrared (FTIR) correlation spectroscopy (CoS) assisted by C 1s near edge X-ray absorption fine structure spectroscopy (NEXAFS). Results show that the amide functional groups of EPS play an important role in its adsorption on goethite, and the adsorption of EPS-proteins on goethite is a function of electrolyte concentration, with increasing adsorption at a higher electrolyte concentration. Results also show that the order in which the EPS functional groups interact and bind with goethite is dependent on electrolyte concentration, where carboxyl and phosphoryl functional groups are the first to adsorb at low electrolyte concentration, while amide groups are the first to adsorb at higher electrolyte concentration. Deconvolution and curve fitting of the amide I band at the end of the adsorption process (~300 min) shows that the secondary structure of proteins is converted from a random coil conformation to aggregated strands, α-helices and turns. This conversion leads to increased adsorption of EPS-proteins and explains the overall adsorption increase of EPS on goethite surfaces with an increasing concentration of electrolyte. Furthermore, the adsorption of the carboxyl functional groups of EPS decreases with increasing electrolyte concentration, likely due to more effective screening of the goethite surface charge with increasing concentration of electrolyte. The integrated results from ATR-FTIR and 2D-CoS allow us to construct a comprehensive overview of EPS-goethite interaction processes at the molecular level, which can be used to improve our understanding of EPS-mineral interactions in the natural environment. These results also provide fundamental information for a better understanding of bacterial biofilm formation on soil and sediment minerals, and facilitate research on the subsequent interaction of nutrients and contaminants with the reactive constituents of biofilms in natural and contaminated environments.