Research On The Photocatalytic Degradation Of Ibuprofen In The Water Using Graphite Phase And Potassium Persulfate

Ibuprofen is a common non-steroidal anti-inflammatory analgesic drug and over-the-counter drug that cannot be completely absorbed by the human body after ingestion.The residual part is usually not completely degraded after being discharged into the wastewater treatment plants,and will eventually be discharged into natural water bodies and exist in the water for a long time.If the aquatic organisms exist in the water containg ibuprofen for a long time,the ibuprofen will be riched in the bodies of aquatic organisms,which will affect the reproductive regulators and embryonic development of aquatic organisms and the balance of the entire aquatic ecosystem in severe cases.Therefore,it is of great significance to research the degradation of ibuprofen in the water to protect the aquatic ecosystem.The photocatalyst graphite phase carbonitride(g-C3N4)has the advantages of good thermal stability,acid and alkali resistance,and strong oxidizing ability.However,it has the disadvantages of the easy recombination of photo-generated holes(h+)and electrons(e-).(S2O82-)has a strong oxidizing property and can reduce the recombination rate of photo-generated holes and electrons photocatalyst by consuming photo-generated electrons of the photocatalyst.In the research,potassium persulfate(PDS)was added to enhance the photocatalytic performance of g-C3N4 in the degradation of ibuprofen under visible light.The study first investigated the preparation,characterization and photocatalytic properties of g-C3N4 to research its physicochemical properties and the synergistic effect of PDS on its photocatalytic degradation of ibuprofen.On this basis,the effect of various factors on the photocatalytic degradation of ibuprofen in the photocatalysis process was studied.Finally,the related experiments of photocatalytic mechanism were conducted to study the reaction kinetics and photocatalytic mechanism of the photocatalytic degradation of ibuprofen by PDS and g-C3N4.The main conclusions are as follows:(1)Using urea as raw material,the photocatalyst g-C3N4 was prepared by thermal polymerization(500°C-1.5 h).The UV-vis(ultraviolet visible absorption spectrum)characterization results showed that the prepared g-C3N4 have strong absorption in the visible light area.And the BET characterization results showed that g-C3N4 has a large specific surface area of 46.62 m2/g.(2)The preliminary experiment showed that the removel rate of ibuprofen was only 62.5% after 4 h photocatalytic reaction with g-C3N4,and the removel rate of ibuprofen was increased to 90.5% after adding PDS into the photocatalytic reaction system,indicating that PDS has synergistic effect on the photolysis of ibuprofen by g-C3N4.(3)Taking ibuprofen as the target pollutant,the effect of factors such as catalyst dosage,initial concentration of ibuprofen,the added amount of PDS,p H,temperature,negative ions and positive ions in water on the photocatalytic degradation of ibuprofen by g-C3N4 and PDS were investigated.The results demonstrated that the optimum dosage of photocatalyst g-C3N4 was 1.0 g/L and the optimal initial concentration of ibuprofen was 10mg/L.The optimum amount of PDS was 3.334 m M and the optimum p H of the reaction solution was 3.The temperature of reaction has little effect on the photolysis of ibuprofen.The inorganic cations Cu2+,Mg2+ and Ca2+ would combine with ·OH from the reaction system to form related hydroxides with photochemical activities,inhibiting the photolysis of ibuprofen by blocking the absorption of light by ibuprofen,but Fe3+ would react with water to form photochemically active intermediates which produce ·OH to promote the photolysis of ibuprofen under light.The presence of CO32-,NO3-and Clwould all inhibit the photocatalytic degradation of ibuprofen.(4)In order to analysis the photocatalytic mechanism of ibuprofen,the quenching experiment of activity species in the photolytic process of ibuprofen,the fluorescence spectra(PL)characterization of samples,the identification of the intermediate products from the photolytic of ibuprofen and the analysis on mineralization degree of ibuprofen were conducted.The results of experimental showed that the process of photocatalytic degradation of ibuprofen accords with the pseudo-first-order kinetics.The addition of PDS could effectively reduce the coincidence rate of photogenerated hole and photogenerated electron from g-C3N4,which enhancing the utilization of h+ and the mineralization degree of ibuprofen.The active species such as e-,h+,O2.-,·OH and SO4·-formed in the reaction all involved in the photolysis process of ibuprofen,and h+ played a leading role in the process.After being photodegraded,ibuprofen would generate a series of small-molecule intermediates such as 4-ethylbenzaldehyde,4-isobutyl phenylethylene,1-(4-lsobutylphenyl)ethanol and 4-isobuthyl-acetophenone which eventually generated inorganic salts and water,laying the foundation for subsequent biological treatment.