Study On Synthesis Of ?-Fe₂O₃/SC₃N₄ And Fluorescence Detection Of Leaching Iron By Carbon Quantum

Fenton oxidation is an efficient method to treat wastewater,but maintaining process a large number of ferrous ions,pH3.0-4.0 and other conditions greatly increase the cost.Therefore,to explore the method of coupling heterogeneous modification to enlarge the feasible pH range and reduce the residual iron ions is a challenge for the preparation of heterogeneous Fenton.The leaching amount of iron is one of the important parameters to evaluate its stability.As a fluorescent probe,carbon quantum dots?CDs?have the advantages of low operating cost and simple process,but their easy agglomeration and hydrolysis features restrict their practical application.How to use different assembly or growth techniques to transform CDs from the unstable dispersed liquid state into multi-dimensional and even macroscopic large chunks of new composite materials is a key research direction for study.According to the above research background,in chapter three,?-Fe₂O₃/SC₃N₄ was prepared for the first time by coupling ?-Fe2O3 with SC3N4 by high temperature solid phase method.The purpose of this chapter is to synthesize a stable heterogeneous Fenton catalyst to reduce the leaching amount of iron ions,enlarge the pH tolerance and realize the recycle of the catalyst.In the fourth chapter,a high quantum yield CDs modified by sulfur and nitrogen was prepared by one-step hydrothermal method.The detection ability of iron ions was evaluated by fluorescence probe method.In the fifth chapter,loading CDs to 3D cellulose hydrogel using cellulose as the matrix and CDs as functional units to explore a new,high efficient and low-cost approach constructing luminescent material was introduced.In this experiment,carbon quantum dots was introduced by dissolving-cross-linking in situ reaction to improve it's stability and enhancement actual detection performance.The conclusions are as follows:?1?The ?-Fe₂O₃/SC₃N₄ catalyst is obtained by coupling ?-Fe2O3 and SC3N4.The nanometer material still has graphite carbon nitrogen skeleton structure,the average particle size is 10 nm,microporous material,the molecule contains the Fe-N bond.Under the optimal experimental conditions,The degradation efficiency of MO,MB,RhB?50.0 mL 50 mg·L-1?were 99.3%,99.4%,97.5%,and the COD remove was 48.9%,50.7%,46.4%,respectively.The leaching amount of iron was in accordance with the standard of wastewater discharge.The efficiency of catalyst was not decreased after five times cyclic catalysis.Moreover,the catalyst remained catalytic under neutral conditions,but the catalytic time increased from 30 min to 120 min.?2?The surface of the CDs is rich in hydroxyl,amino,sulfonic and carbonyl structures.The average particle size is 20 nm,and the ultraviolet absorption spectra have obvious absorption peaks in 233 nm and 343 nm.The maximum excitation and emission wavelength are 350 and 445 nm respectively.The half peak width is 74.0 nm,quantum yield reached 32.2%.The amino and sulfonic groups formed on the surface of the carbon quantum dots can cause the surface energy limit of the carbon quantum dots to stabilize,which leads to the single radiation compound mode.And the linear range for detection of Fe3+ is 5.00-560 ?mol L-1,the linear regression equation is?F0-F?/F0=-0.02330+1.751c,R2=0.9970,and the detectable limit is 5.00 ?mol L-1.The iron content was 4.67 mg/tablet and the standard deviation was 0.12.The recovery rate was 98.0%-101.2%.The leaching amount of ?-Fe₂O₃/SC₃N₄ iron was 1.71 ppm,and the standard deviation was 0.13.There is no significant difference compared with the classical two nitrogen phenanthrene detection method.Compared with the recently reported method of quantum dot detection,this method is simpler,wider linear range,lower detection limit and stronger resistance.?3?The carbon quantum cellulose hydrogel surface is rich in the the carbon and carbon double bond,methylene,carbonylm and hydroxyl.The maximum excitation and emission wavelength are 350 and 398 nm respectively.The half peak width of 88.0 nm.The linear range for detection of Fe3+ is 2.00×10-4-4.00×10-1 mmol L-1,the linear regression equation is F/F0=-0.19391gc+0.2363,R2=0.9978,the detectable limit is 200 nmol L-1.The iron content was 4.75 mg/tablet and the standard deviation was 0.12.The recovery rate was 98.00%-101.2%.The leaching amount of ?-Fe₂O₃/SC₃N₄ iron was 1.77 ppm,and the standard deviation was 0.12.There is no significant difference compared with the classical two nitrogen phenanthrene detection method.The use of cellulose hydrogel not only can stabilize the carbon quantum dots and keep them stable at room temperature,but keep lower detection limit in Fe3+detection.