Study On Photolytic Degradation And Mechanisms Of Acyclovir In Aqueous Environment

In recent years,pharmaceutical and personal care products?PPCPs?is causing particular concern as a kind of emerging enviromental pollutants.Acyclovir,the second generation of broad-spectrum antiviral drug,has been widely used in all kinds of infections caused by herpes simplex virus.Studies have shown that it mainly distributed in the water phase on account of its lower LogKOW and could easily enter rivers through a variety of ways,posing threats to the aquatic ecosystem and human.In recent years,in Guangzhou municipal sewage sewage treatment plant in the detection of acyclovir this trace of organic pollutants.The photochemical behavior of acyclovir in natural water bodies and the byproducts and their toxicity in photolysis processes,as well as the ecological risks of aquatic organisms,are of concern.Photochemical degradation is an important way to remove pollutants like PPCPs in the surface water.Organic pollutants present in natural water environments will undergo complex photochemical reactions under light irradiation.At present,the research on photodegradation of acyclovir is lacking in systematic,and the influence and mechanism of photolysis mechanism,photolysis product and environmental factors are not clear.In this paper,we investigated the photochemical kinetics,photodegradation mechanism,photolysis path and photodegradation of acyclovir in simulated water under simulated sunlight.The effect of environmental factors on the photolysis of acyclovir was investigated by simulating the natural water,and the influence mechanism was analyzed,in order to gain a better understanding of its migration and transformation in natural water and provide theoretical basis for evaluating its environmental and ecological risks.First of all,the photodegradation behavior of acyclovir at different initial concentrations and pH was studied under simulated sunlight,and the photon yield of acyclovir was determined by potassium pyrrole.Then the photolysis mechanism of acyclovir was studied by quenching experiments.The results show that acyclovir can undergo photodegradation under simulated sunlight,and its degradation process is consistent with pseudo-first-order kinetics.Photodegradation of acyclovir can be divided into two parts: direct and indirectphotolysis.Within the concentration range of 10 mg·L^-1,the initial concentration had little effect on the photodegradation.The change of pH value,however,significantly affected the photodegradation rate of acyclovir: the higher the pH value,the faster the degradation rate of acyclovir.It is more likely that photolysis of acaclovir is more likely to be inferred from the dissociation morphology of acyclovir.The effects of the various forms of inorganic nitrogen?NO₃^-,NO₂^-,NH₄⁺?,the change of pE value,the presence of humic acid and bicarbonate ion in the water environment were also studied.The results showed that NO₃^-and NO₂^-promoted the degradation of acyclovir and the effect was stronger once the concentration of NO₃^-and NO₂^-was increased,which was mainly due to its abilities of producing reactive oxygen species in the light to promote acyclovir's photolysis.NH₄⁺has no effect on the photolysis of acyclovir because NH₄⁺has no light absorption in the UV-visible range,neither inhibiting acyclovir photolysis by competitive absorbance,producing reactive oxygen species.The effect of inorganic nitrogen on the photolysis of acyclovir during the change of pE value showed that the main influence factor on the photolysis of acyclovir was observed to be NO₂^-.when NO₂^-and NH₄⁺coexist.When NO₃^-and NO₂^-coexist,however,both of which have antagonistic effects on the photolysis of acyclovir.Humic acid has an inhibitory effect on the photolysis of acyclovir due to the presence of competitive absorption of humic acid and acyclovir and the quenching of reactive oxygen species.HCO₃^-has a promoting effect on the indirect photolysis of acyclovir,since HCO₃^-reacts with ·OH producing a highly selective oxidant,CO3·-,which reacts with acyclovir and hence photolysis.Products in the photodegradation process of acyclovir were studied using HPLC/MS/MS,and its toxicities were studied by the method of luminous bacteria.Based on the analysis of the spectrum,it is deduced that the photolysis product of acyclovir is mainly the product of ·OH addition,and the photolysis reaction path is mainly the photocatalytic pathway of ·OH.The photoluminescence experiments show that acyclovir photodegradation process produces higher risk intermediates than the parent product.