Study On Photochemical Behavior And Photocatalytic Degradation Of Naproxen In Aqueous Environment

In recent years,pharmaceutical and personal care products(PPCPs)is caused widespreadly concern among the academic community and the public which is occur in natural aquatic environment widely and threats to human health and ecological and environmental security.As a kind of emerging environmental pollutants,a wide range of PPCPs includes antibiotics,synthetic musk,pesticide and herbicide,etc.They enter the environment in the process of production,transportation,storage and use,and are present in trace concentrations.Because they are generally difficult to biodegradation characteristics,the sewage treatment plant of the traditional processing technology is difficult to completely remove it at the same time,also in was constantly introduce environment,often known as "pseudo persistent pollutants".For PPCPs,the photodegradation of water environment is an important non-biodegradation pathway,so it is very important to study the photodegradation behavior of PPCPs in water environment.Naproxen(alpha-methyl-6-methoxy-2-naphthyl acetic acid)is a commonly used non-steroidal anti-inflammatory drugs,which is one of the world's major antipyretic analgesics and one of the top four non-prescription drugs.At present,the research on the photodegradation of naproxen is nonsystematic,and it is undefined about the mechanism of photodegradation mechanism,environmental factor and its effects.The adsorption and photocatalytic effects and mechanisms of co-existing metal oxidation are rarely noticed and understood particularly.This study selected naproxen as the model compounds,to discuss the photodegradation kinetics in the pure water,the photodegradation mechanism,and by simulating natural water bodies,a research on the environmental factors and its effect on naproxen,the influence of photodegradation,and analyzes the influence mechanism,aims at a deep understanding of the environment of naproxen photochemical behavior,to evaluate its environment to provide theoretical basis and the ecological risk.At the same time,in order to control and eliminate the naproxen pollution to the environment,use of water environment in the coexistence of metal oxide(hydroxyl)iron oxide as photocatalytic material,studies its adsorption and degradation of naproxen,explore the coexistence of metal oxide to naphthalene raw light catalytic removal of application.Photodegradation mechanisms of naproxen were researched.The results revealed that under UV the photodegradation pathways of naproxen proceed via pseudo first-order kinetics well.Quenching experiments demonstrates that the photodegradation of naproxen by UV is the sum of the degradation by direct photodegradation and self-sensitization in the aquatic environment.During naproxen photodegradation,the contribution rates of ·OH,1O2 and O2·-for the photodegradation are 21.12%,15.94%and 64.14%respectively.The direct photodegradation contributed to the main degradation of naproxen with little contributed of self-sensitization,its reaction rate is greater than that of self-sensitized photodegradation.Increased the initial concentration of naproxen,the photodegradation rate of naproxen was decreased then.The pH of the solution can change the existence form of naproxen,which is the electron cloud density of naproxen molecule,and the stability of the group.When pH=7,the photodegradation rate of naproxen was the least,and its photodegradation was excellent:acid>alkaline>neutral.Elevated temperature can be beneficial to the photodegradation of naproxen,but in general,it has little effect.In addition,the concentration of dissolved oxygen in solution is beneficial to self-sensitized photodegradation,but it is not conducive to direct photodegradation.In this paper,the effects of dissolved substances and their compound state on the photodegradation of naproxen were studied.Adding NO3-or NO2-can inhibit the photodegradation of naproxen.Because NO3-and NO2-can compete with naproxen to absorb photons and produce light shielding;at the same time,NO3-can increase the ·OH in the system,and NO2-in the quenching system,all are shown as inhibition of the photodegradation of naproxen.While NH4+ was not significantly.For halogen ion,Cl-and Br-both inhibit the photodegradation of NPX,while I-has a promotion.Because the halogen ion can not only eliminate 3NPX*,inhibit the direct photodegradation of NPX,but also produce the active species,promote the s self-sensitization of NPX,and generate optical shielding for the NPX.However,since the halogen ion is irradiated by ultraviolet light,it can also produce its own homogeneity,and produce the oxidized secondary halogenated HXO.The overall expression of the inhibition of NPX photodegradation was:Cl->Br->I-.Metal ions(Fe3+?Fe2+?Cu2+?Zn2+)all inhibit the photodegradation of NPX.Because metal ions(Fe3+?Fe2+?Cu2+?Zn2+)coincide with the absorption spectrum of NPX;secondly,metal ions combine with H2O to form complexes to reduce the transmittance of the reaction system,while producing ·OH to promote the photodegradation of NPX;third,Fe3+ and Cu2+ can produce precipitation with OH-,which affects the photodegradation of NPX.In surfactant,CTAB can promote the photodegradation of NPX,while SDBS and Tween-80 are inhibitory.Three kinds of surfactants compete absorb photons with NPX,and the solubilization and electrostatic effect are associated with surfactant molecules on the surface of the charged,which affect the NPX photodegradation.HA can inhibit the photodegradation of NPX.On the one hand,there are partial spectral overlap between HA and NPX.On the other hand,HA produces excited state 3HA*,which promotes NPX photodegradation.Finally,HA can quench 3NPX*and affect NPX degradation.The addition of acetone can promote the production of 3NPX*,so promoting the photodegradation of NPX.-OH is produced by H2O2 under the UV irradiation,which promotes the photodegradation of NPX.HCO3-inhibits the photodegradation of NPX because of the removal of the ·OH and the shielding effect lightly.The two pigments,methylene blue(MB)and crystal violet(CV),affect the transmittance of the system due to its own color,and overlap with the absorption spectrum of NPX,so the photodegradation of NPX is inhibited.In addition,this paper also examined the interconversion between nitrogen and iron systems under different pE values,and discussed the effects of different forms of nitrogen or iron on NPX.The results show that there is antagonism between different forms of nitrogen and there is a synergistic effect between different forms of iron.The photodegradation of NPX in tap water and pearl river water was studied.The experimental results showed that the photodegradation rate of NPX in tap water and pearl river water was slower than that of pure water,and the rate constant of photolysis was 0.0220 min-1 and 0.0172min-1 respectively.Finally,?-FeOOH,a common suspended substance in the water,was selected as the research object to investigate its influence on the migration and reintegration of NPX in aqueous solution.The results showed that the initial concentration and temperature rise were beneficial to the adsorption of NPX by ?-FeOOH,which is the result of diffusion drive and molecular thermal motion.At pH-7 the effect of NPX adsorption performance of ?-FeOOH is best because the pH changes the electrostatic adsorption and bond adsorption between ?-FeOOH and NPX.Lagergren's quasi-secondary dynamics model and the Langmuir isothermal model can better describe the adsorption process of NPX by?-FeOOH.The internal diffusion process is the control step of the adsorption reaction,but it is not the control step only.According to thermodynamic analysis,the adsorption process of NPX by ?-FeOOH is spontaneous,endothermic,and degree-of-freedom process.Increasing ?-FeOOH concentration can promote the photodegradation of NPX,the relationship between ?-FeOOH concentration and reaction rate constant is k=0.05577[FeOOH]0.1394.When ?-FeOOH concentration is certain,the photodegradation rate of NPX decreases with increase of initial concentration in the solution.The relationship between the concentration of NPX and the reaction rate constant is k=0.03790[NPX]-0.1673.?-FeOOH photocatalysis of NPX is the result of a combination of semiconductor photocatalysis and surface coordination.To conclude,NPX can be degraded by direct light degradation and self-sensitized photodegradation in aqueous solution,and the photodegradation is affected by dissolved substances and suspended objects.This study reveals the photocatalytic behavior and mechanism of NPX in aqueous solution,and it is of great significance to predict the migration and trend of NPX in the water environment,and to explore the removal of NPX by the co-existence of photocatalysis.