Highly hydrophilic extracellular polymeric substance (EPS) with gel-like structure seriously plagues the development of sludge deep dewatering. Oxysulfur radicals-based oxidation driven by iron-bearing mineral proposes a promising strategy for effective EPS decomposition. However, the transformation and involved interaction mechanisms of aromatic proteins are still controversial due to the complex EPS structure. Herein, sulfite mediated siderite (denoted as Fe(II)/S(IV)) was developed for targeted transformation aromatic amino acids in EPS oxidation to strengthen sludge solid-liquid separation. The enhanced sludge dewaterability were benefited from the Fe(II)/S(IV) bonded interaction assisted by Fe3+/Fe2+ as redox interface that facilitating the release of intracellular bound water via diminish the hydrophily and bind strength with solid protons. The amide region nitrogen of aromatic amino acids (especially tyrosine and tryptophan) originating from EPS presented looser structure and lower spatial site resistance, which were attributed to the exposure of hydrophobic sites in amino groups after Fe(II)/S(IV) treatment. Furthermore, the effective decline of aromatic amino acids in inner layer-EPS (loosely bound EPS and tightly bound EPS) was directed from Fe-N targeted interaction by triggering a series of sulfate-based radical chain reactions. The good correlation between electron transfer amount (R2 = 0.926) and Fe-N (R2 = 0.925) with bonding interaction demonstrated that the complexation of aromatic amino acids with Fe sites on siderite/sulfite via Fe-N bonds, accounting for efficient sludge solid-liquid separation. This study deepens the understanding of sludge organic matter targeted transformation and provides a tactic for iron-based conditioning of sludge.

中文翻译：

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在污泥固液分离中，通过亚硫酸盐介导的铁氧化还原循环促进细胞外聚合物物质的芳香族氨基酸靶向转化


具有凝胶状结构的高亲水性胞外聚合物物质 （EPS） 严重困扰污泥深层脱水的发展。由含铁矿物驱动的基于氧硫自由基的氧化提出了一种很有前途的有效 EPS 分解策略。然而，由于 EPS 结构复杂，芳香族蛋白的转化和涉及的相互作用机制仍然存在争议。本文开发了亚硫酸盐介导的菱铁矿（表示为 Fe（II）/S（IV））），用于在 EPS 氧化中靶向转化芳香族氨基酸，以加强污泥固液分离。增强的污泥脱水性受益于 Fe3+/Fe2+ 作为氧化还原界面辅助的 Fe（II）/S（IV） 键合相互作用，通过减少亲水性和与固体质子的结合强度来促进细胞内结合水的释放。源自 EPS 的芳香族氨基酸（尤其是酪氨酸和色氨酸）的酰胺区氮结构更松散，空间位点阻力较低，这归因于 Fe（II）/S（IV） 处理后氨基疏水位点的暴露。此外，内层-EPS （松散结合的 EPS 和紧密结合的 EPS） 中芳香族氨基酸的有效下降是由 Fe-N 靶向相互作用通过触发一系列基于硫酸盐的自由基链反应来指导的。电子转移量 （R2 = 0.926） 和 Fe-N （R2 = 0.925） 与键合相互作用之间的良好相关性表明，芳香族氨基酸与菱铁矿/亚硫酸盐上的 Fe 位点通过 Fe-N 键络合，解释了高效的污泥固液分离。本研究加深了对污泥有机质靶向转化的理解，并为污泥的铁基调节提供了一种策略。