Preparation Of Nitrogen-doped Graphene-like Complex Iron-based Catalyst And Its Mechanism For Removing Refractory Organic Pollutants In Water

In the case of water shortage,due to the rapid development of economy and industry caused serious water pollution,making the original tension of water resources utilization close to or even exceed its threshold.Advanced oxidation process as the main wastewater treatment technology is favored by researchers.However,the advanced oxidation process requires additional energy to achieve excellent removal efficiency,which causes great energy consumption.In contrast,although the iron-carbon micro-electrolysis system stacked by zero-valent iron and activated carbon has low cost,it is difficult to efficiently remove refractory organic pollutants.In this paper,in order to efficiently remove refractory organic pollutants in water,chemical complex iron-based carbon materials were constructed on the basis of iron-carbon micro-electrolysis,aiming to develop new iron-based catalysts with low cost,stability and efficiency,so as to evaluate their catalytic performance for organic pollutants and explore the degradation mechanism of refractory organic pollutants.The main contents of this paper are as follows:（1）Iron-based catalyst CHOF-900 was prepared at high temperature using hydrogen bond organic framework as precursor.The structure of CHOF-900 was characterized by zero-valent iron coated with graphene-like complex iron oxide.Material characterization confirmed the formation of Fe-O chemical complex between iron species and graphite carbon.Density functional theory calculation results showed that the surface electron polarization distribution of CHOF-900 formed a rich-poor electron microzone,where the electron density near Fe was high and the electron density on the aromatic ring was low.In the air-saturated aqueous suspensions of CHOF-900,bisphenol A was obviously degraded,and the catalytic performance of CHOF-900 was superior to that of iron-based porous organic carbon materials.（2）Based on the surface acidification modification of CHOF-900,a new iron-based catalyst ACHOF-900 was obtained.The main structure of ACHOF-900was zero-valent iron with nitrogen-doped graphene-like complex iron oxide.Fe-πelectrostatic force was formed on the surface of ACHOF-900,making the surface Fe species as electron-rich center and aromatic ring as electron-poor center,which promoted the adsorption of water molecules or organic pollutants in the electron-poor area on the surface.Electrons on water molecules or organic pollutants were biased near the Fe species on the surface of ACHOF-900,blocking zero-valent iron corrosion in ACHOF-900 catalysts.ACHOF-900 system showed good stability and excellent catalytic activity in the degradation of most organic pollutants,without additional energy to reduce the cost.（3）Based on the characterization of different instruments and theoretical calculation,it was revealed that hydroxylated organic pollutant bisphenol A was adsorbed on the graphene-like aromatic structure of ACHOF-900 throughπ-πor hydrogen bonding,and was affected by the surface Fe-πelectrostatic force.The strong molecular orbital interaction between the adsorbed organic matter and the aromatic structure of the catalyst induced the electron delocalization of the adsorbed organic matter to be captured by dissolved oxygen around the Fe species,resulting in the cleavage of the hydroxyl functional groups of the adsorbed organic pollutants into superoxide radicals(O₂^·-)and the further hydrolysis of the generated organic cation radicals.It was also confirmed that the non-hydroxylated organic pollutants such as diphenhydramine were first cracked on the surface of ACHOF-900 by water molecules to produce O₂^·-,and then the diphenhydramine was oxidized to form hydroxylated products,followed by repeated interfacial reactions.This not only could remove most refractory organic pollutants in water without external energy,but also ensured the stability of iron species in ACHOF-900.