Photodegradation Behavior Of Typical Antiviral Drugs For COVID-19 In Water Environment

Chloroquine phosphate（CHQ）is a common antimalarial drug,and abidol hydrochloride（ABD）is a commonly used antiviral drug.As typical pharmaceutical and personal care products（PPCPs）,the two drugs have played a significant role in the global spread of the novel coronavirus pneumonia（COVID-19）.The two drugs were produced and used in large quantities during the epidemic.In the human body CHQ and ABD may not be completely absorbed,the remaining part is excreted out of the body in the form of feces,or passed through hospital sewage,domestic wastewater and other ways into the city drainage pipe network,and then got into the sewage treatment plant and natural water environment.Therefore,it is of great significance to understand the photochemical conversion process of chloroquine phosphate and abidol hydrochloride in aqueous environment.Chloroquine phosphate and abidol hydrochloride are the main research objects in this paper.This research investigates their photodegradation reaction kinetics,degradation mechanisms and influencing factors under simulated sunlight.The main experimental contents and conclusions are as follows:Study on the degradation of CHQ under simulated sunlight:（1）The degradation curve of CHQ under simulated sunlight conformed to the pseudo-first-order reaction kinetics equation,and the photodegradation reaction rate was negatively correlated with the initial concentration;the photodegradation rate was related to its protonated form.In the range of p H=6.0-10.0,the degradation rate increased with the p H increased.（2）Two common humic substances（humic acid and fulvic acid）in natural water environment played a photo-shielding role in CHQ photodegradation,inhibiting its photodegradation.The degree of inhibition increased with the increase of the concentration of humic acid and fulcrum acid.Under different p H conditions,the photoshielding was dominant.Common cations(Fe³⁺,Ca²⁺,Mg²⁺,Mn²⁺)and anions(NO₃^-、Cl^-、SO₄^2-、HCO₃^-)in water had little effect on the photodegradation of CHQ.（3）The photodegradation reaction rate of CHQ in the secondary effluent of sewage treatment plant was lower than that in the pure water system.The photodegradation reaction rate in different natural water bodies was also slower than that in the pure water system,and was related to water quality.The photodegradation rate decreased as the water quality got worse.The degradation rate in different water systems:pure water>Liangzi Lake>Yangtze River>East Lake>Yujia Lake.（4）The degradation of CHQ under simulated sunlight was mainly direct photodegradation with the self-sensitized degradation involving singlet oxygen.HR-LC-MS was used to detect the photodegradation products of CHQ.Four main photodegradation products of CHQ were detected,and their structures and possible photodegradation pathways under simulated sunlight were deduced.Toxicity tests of luminescent bacteria showed that CHQ produced more toxic intermediate products during photodegradation.Study on the degradation of ABD under simulated sunlight:（1）The degradation curve of ABD under simulated sunlight conformed to the pseudo-first-order reaction kinetics equation,The photodegradation rate was proportional to the initial concentration.The photodegradation rate was related to its UV absorption spectrum at different p H.In the range of p H=5.0-9.0,the degradation rate increased with the p H decreased.（2）Two common humic substances（humic acid and fulvic acid）in natural water environment played a photo-shielding role in ABD photodegradation,inhibiting its photodegradation.The degree of inhibition increased with the increase of the concentration of humic acid and fulcrum acid.Under different p H conditions,the photoshielding was dominant.Common cations in water had little effect on the photodegradation of ABD.Among the common anions,HCO₃^-and SO₄^2-slightly inhibited the photodegradation of ABD.（3）The photodegradation reaction rate of ABD in the secondary effluent of sewage treatment plant was lower than that in the pure water system.the photodegradation reaction rate in different natural water bodies was also slower than that in the pure water system,and was related to water quality.The photodegradation rate decreased as the water quality got worse.The degradation reaction rate in different water systems:pure water>Liangzi Lake>Yangtze River>East Lake>Yujia Lake.（4）The degradation of CHQ under simulated sunlight was mainly direct photodegradation with the self-sensitized degradation involving singlet oxygen and superoxide anion radical.HR-LC-MS was used to detect the photodegradation products of ABD.Five main photodegradation products of ABD were detected,and their structures and possible photodegradation pathways under simulated sunlight were deduced.The toxicity test of luminescent bacteria showed that the toxicity of ABD was significantly reduced during the photodegradation process.