黄铁矿-Fe(Ⅲ)表面Lewis酸位点增强微囊藻毒素催化水解的机制

Mechanism of Hydrolysis of Microcystins Enhanced by Lewis Acid Sites on the Surface of Pyrite-Fe(Ⅲ)

天然黄铁矿(Pyrite)在高温(60℃)下能有效降解(k=0.072 min^(-1))水中微囊藻毒素(MCs),但突破高温瓶颈、实现常温条件[(25±5)℃]下MCs的高效降解仍是目前水处理技术的难点.本文发现外加铁离子(Fe^(3+),FeCl_(3))能加速Pyrite常温体系对微囊藻毒素-RR(MC-RR)的水解效率(水解贡献率77.94%),其降解速率常数(0.36 h^(-1))是单独Pyrite体系(0.12 h^(-1))的3倍.通过X射线光电子能谱仪(XPS)、循环伏安法(CV)、原位表面衰减全反射红外光谱(in situ ATR-FTIR)和密度泛函理论(DFT)等研究发现,外加Fe^(3+)通过形成Fe(Ⅲ)—O键增加了Pyrite表面Lewis酸铁位点数,再通过其与C=O配位实现了对MC-RR酰胺键的水解.此外,外加的Fe^(3+)还能将Pyrite表面多价态硫物种(S_(n)^(2-),S_(2)^(2-))氧化为单质硫(S0),通过形成氢键—NH…S进一步促进MC-RR的水解.本研究不仅为蓝藻水华治理提供了一种常温矿物处理技术,还为自然水体中酰胺类有机污染物的自净机制提供了理论依据.

Natural mineral(Pyrite)can effectively degrade microcystins(Microcystins,MCs)in water at warm temperature(60℃)(k=0.072 min^(-1)),but how to break through the heat bottleneck and attain efficient degradation of MCs at room temperature[(25±5)℃]are still a technical issue in water treatment nowadays.In this study,the addition of iron ions(Fe^(3+),FeCl_(3))can accelerate the hydrolysis efficiency of microcystins-RR(Microcystin-RR,MC-RR)in pyrite system at room temperature(hydrolysis contribution rate 77.94%),and the degradation rate constant(0.36 h^(-1))was three times higher than that of pyrite alone(0.12 h^(-1)).X-ray photoelectron spectroscopy(XPS),cyclic voltammetry(CV),in situ attenuated total reflection-Fourier transform infrared spectroscopy(in situ ATR-FTIR)and density functional theory(DFT)suggested that the addition of Fe^(3+)enhanced the amount of iron sites of Lewis acid on pyrite surface by forming Fe(Ⅲ)—O bond,and then hydrolyzed MC-RR amide bond through its coordination with C=O.Additionally,the addition of Fe^(3+)can oxidize the multivalent sulfur species on the surface of pyrite(S_(n)^(2-),S_(2)^(2-))to elemental sulfur(S_(0)),further promoting the hydrolysis of MC-RR by forming hydrogen bond(—NH…S).This study not only provides a normal temperature mineral treatment technology for cyanobacteria bloom treatment,but also provides a theoretical basis for the self-purification mechanism of amide organic pollutants in natural water.