Application Of Triazine Framework Composites For Activation Of Persulfate To Degrade Sulfonamide Antibiotics

Advanced peroxynite-based oxidation processes（P-AOPs）have received increasing attention in the environmental field as one of the most commonly used techniques for the removal of novel antibiotic organic pollutants in aqueous remediation problems.However,the design and development of effective activators with outstanding catalytic activity and high stability remains extremely challenging in Fenton-like reactions.Covalent triazine frameworks（CTFs）are a class of nitrogen-rich porous covalent organic polymers with a basic triazine ring as the building block.CTFs not only have the properties of crystalline semiconducting covalent organic polymers,but have high nitrogen content,large specific surface area,superior porosity and excellent thermal/chemical stability,making them ideal for use in electrocatalysis,photocatalysis,energy storage devices,and other research fields.Based on this,a covalent triazine framework material（CTF-1）with a two-dimensional ortho-hexagonal geometry was selected as a carrier for catalytic reactions in this thesis,and a series of catalysts were rationally designed and prepared through strategies such as metal doping,pyrolysis-derived composites and functionalised modifications.At the same time,the catalyst-activated persulfate-based Fenton reaction is highly efficient in removing micro-pollutants—sulfonamide antibiotics from the water column.The specific studies in the thesis are as follows:（1）Construction of Fe-N bonded porous carbon nanotube composites Fe-N@NPC for the catalytic degradation of sulfamethoxazole by activated peroxymonosulfate（PMS）.First,the target materials were prepared in 2 steps.In the first step,FeCl₃was doped on CTF-1 2D nanosheets by wet impregnation obtain the inexpensive precursor material FeCl₃@CTF-1;In the second step,a highly active catalyst Fe-N@NPC-A was prepared by optimizing the pyrolysis temperature（700℃）.5mg/L Sulfamethoxazole（SMX）was used as a model pollutant.The results of the catalytic experiments after screening the reaction conditions showed that Fe-N@NPC-A/PMS system could achieve 98.97%SMX removal rate and 41%mineralization rate within 60 min,which were higher than Fe-N@NPC-B（61.6%）and Fe-N@NPC-C（65.6%）,respectively.After 4 recycling experiments,the removal rate is still more than 89%.Analysis of the degradation mechanism and free radical reaction pathway of SMX on Fe-N@NPC-A by electron spin resonance（ESR）and free radical capture experiments.Finally,an objective analysis of the practical significance and application potential of Fe-N@NPC in environmental remediation.（2）Synthesis of ferric citrate modified CTF-1（Fe@CTF-1）.Fe@CTF-1 was driven by visible light to enhance PMS activation and catalytic degradation of sulfonamide antibiotics（sulfamethoxazole,sulfamethazine,sulfamethoxazole）.Firstly,1,4-dicyanobenzene was chosen as the monomer for the synthesis of CTF-1 through a strong organic acid-catalyzed thermal polycondensation process.Secondly,a functionalized composite Fe@CTF-1 with homogeneous dispersion of iron ions was prepared by a hot solvent method.In this work,the Fe-CA modified CTF-1 was carefully designed by fine-tuning the CTF-1 energy band,and the conformational relationships were explained in terms of structural properties and experimental mechanisms.Specifically,the Fe@CTF-1 is mainly composed of Fe-（Ⅱ）,which is a crystalline semiconductor with narrow band gap and is a bridge for photoexcited charge transport,and the Fe-CA modification significantly broadens the visible light absorption range of CTF-1 and improves the redox（ORR）ability.In particular,Fe（Ⅱ）acts as an active centre to act an electronic"electron relay"to accelerate charge separation and transport.The experimental results showed that at an initial concentration of 10 mg/L of SMX,the optimum ratio of 5%Fe@CTF-1 in the Fe@CTF-1/visible light/PMS system exhibited 100%degradation and 39.6%mineralization rate of sulfamethoxazole within30 min,which was higher than that of the pure CTF-1 system（48.1%）,PMS（42.8%）,CA@CTF-1（70%）and Fe-CA（78%）,respectively.The effect of Fe@CTF-1 on the degradation performance of SMX was objectively evaluated by initial pH,PMS concentration,different concentrations of SMX and catalyst concentration.Crucially,Fe@CTF-1 was capable of simple recovery and well reusability,remaining stable at84%even after 4 cycles.The possible degradation mechanism was explored by different methods such as active species capture experiments,electron spin resonance experiments（ESR）and corresponding photoelectrochemical test analysis.This work provides a viable pathway for the rational design of high-performance and low-cost photocatalysts for environmental remediation.