Study On Degradation And Mechanism Of Chloroquine Phosphate In UV Advanced Oxidation Systems

After outbreak of COVID-19,chloroquine phosphate（CQP）has received widespread attention as a recommended treatment for novel Coronavirus.Massive discharge of CQP will bring potential harm to the ecological environment.At present,there are few studies on CQP removal in environment,most of which focus on its direct photodegradation,and the degradation efficiency is relatively low.Thus,it is necessary to find more efficient treatment methods for degrading CQP.The degradation of CQP was investigated in ultraviolet（UV）/persulfate（PS）,UV/peroxymonosulfate（PMS）,and UV/hydrogen peroxide（H₂O₂）systems.The degradation efficiencies were compared with UV,oxidant and sunlight systems.The second-order rate constants of CQP with hydroxyl radical（HO·）and sulfate radical（SO₄^-·）were determined by competition kinetics experiments.Main active species were determined by kinetic model,alcohol quenching experiment and nitrobenzene（NB）molecular probe experiment.The effects of oxidants concentration,p H,and common inorganic anions on the degradation of CQP in three systems were also studied systematically.Besides,three kinetic models were established to predict the trend of concentration of CQP and major free radicals to explore the influence mechanism.The principal pathways of CQP degradation were proposed by the analysis of liquid mass spectrometry.Then the mineralization rate was investigated by total organic carbon（TOC）analysis.In addition,the change of oxidants concentration was also evaluated.Finally,the energy consumption of three systems was evaluated based electrical energy per order（EE/O）calculation.The main conclusions of this paper were as follows:（1）Research results showed that CQP could be degraded efficiently in UV/PS system.The second-order rate reaction constants of CQP with HO·were determined 8.94×10⁹,8.85×10⁹,1.01×10¹⁰ and 8.89×10⁹ M^-1s^-1 and that of CQP with SO₄^-·were 1.22×10¹⁰,1.39×10¹⁰,1.76×10¹⁰ and 1.94×10¹⁰ M^-1s^-1 at p H 4.8,6.9,8.8 and 10.8,respectively.Main active species was SO₄^-·in this system.The degradation rate of CQP increased with the increase of PS concentration.Strong base condition,Cl^-and HCO₃^-inhibited CQP degradation.The mineralization rate increased with the increase of PS concentration and p H value.The N-de-ethylation,cleavage of the C—N bond and hydrogen abstraction were proposed as the principal pathways of CQP conversion to small molecule organic intermediates,then to small molecule inorganic products gradually.（2）In UV/PMS system,CQP can be degraded efficiently.Both SO₄^-·and HO·were determined to be main active species.The degradation rate of CQP could be promoted by improve PMS concentration and p H.Cl^-inhibited the degradation of CQP slightly,and HCO₃^-had no significant effect on CQP degradation.The mineralization rate increased with the increase of PMS concentration.The N-de-ethylation,cleavage of the C—N bond,hydrogen abstraction and N-oxide were proposed as the principal pathways of CQP conversion to small molecule organic intermediates,then to small molecule inorganic products gradually.（3）In UV/H₂O₂ system,CQP can be degraded efficiently.The degradation contribution of CQP under neutral condition was almost 100%from HO·.The degradation rate of CQP increased with increasing the concentration of H₂O₂,but excessive H₂O₂ and too high p H could inhibit CQP degradation.The addition of Cl^-and HCO₃^-had no significant effect on CQP degradation.The mineralization rate increased with the increase of H₂O₂ concentration.The N-de-ethylation,cleavage of the C—N bond,hydrogen abstraction and N-oxide were proposed as the principal pathways of CQP conversion to small molecule organic intermediates,then to small molecule inorganic products gradually.（4）In the three systems,the oxidants did not degrade significantly in the study time range,and the decay rate was much lower than that of CQP,indicating that they had great application potential.The energy consumption of three systems was evaluated based EE/O calculation,and it followed the trend of UV/PMS>UV/H₂O₂>UV/PS.