Study On The Degradation Efficiency And Mechanism Of Typical Fibrates Pharmaceuticals By N And F Doped TiO₂ Nanotube Arrays Induced By Sunlight

It has been acknowledged that Bezafibrate（BZF）and ciprofibrate（CPF）as typical fibrate lipid regulators are widely used with large dosage.Due to their special physicochemical properties,it seems rather difficult to remove them by the traditional treatment process of water treatment plants,leaving a large amount of residual in various kinds of water and leading to serious pollution to the water environment.Simulated sunlight irradiation N,F doped Ti O₂nanotube arrays（NF-TNTAs）has been regarded as a green and efficient water treatment technology.The present study employed this technique to degrade BZF and CPF,and examine the kinetics of the photocatalytic process,efficiency,mechanism,common water quality influence factors and mechanism.The photocatalytic degradation of NF-TNTAs induced by simulated sunlight via BZF and CPF can conforms with the first-order kinetic model.·OH,·O₂^-,h⁺and ¹O₂ can actively work during the photocatalytic degradation of BZF and CPF,and the contribution of the four active substances are varied with the change of p H.In general,·O₂^-can contribute most among all p H conditions concerning its fixed yield and promotion of ROSs production and circulation.The contribution of ¹O₂ is second only to·O₂^-among all p H conditions.h⁺can supply much contribution under p H=5 comparing with p H=7 and 9.The contribution of·OH under p H=7 is greater than p H=5 and 9.The degradation products and pathways of BZF and CPF were analyzed by combining computational chemistry and high resolution mass spectrometry,and 7 BZF and 5 CPF degradation products were detected respectively.There are a total of 4 active sites of BZF structure vulnerable to be attacked by active substances.It thus can be speculated that there are at least 5 possible degradation paths:aromatic ring hydroxylation,amide-carbonyl oxidation fracture,oxidation or reduction dechlorination,oxidation to remove the fibrate chain and further oxidation after de-fibrate chain.Besides,there are a total of 3 active sites of CPF structure vulnerable to be attacked by active substances.The results suggest 3 possible degradation paths:aromatic cyclic hydroxylation,ring opening of benzene epoxidation,further oxidation of benzene ring after de-fibrate chain and cyclopropyl removal.It also can be drawn from the results that the concentration,p H,DO and soluble substances in water can influence the process of photocatalytic degradation.The degradation efficiency of both BZF and CPF can increase with the decrease of the concentration,and moreover the relationship between the photocatalytic degradation rate and the initial concentration of the target degradation was in line with the Langmuir-Hinshelwood pseudo-first-order kinetic model.Different p H conditions（p H=5,7 and 9）had significant effects on the photocatalytic degradation efficiency of BZF and CPF in NF-TNTAs.The degradation rate was the highest at p H=5,followed by p H=7,while the degradation rate was the lowest at p H=9.The increase of DO can improve the degradation efficiency of BZF and CPF.Five kinds of anions(i.e.,NO₃^-,CO₃^2-/HCO₃^-,HPO₄^2-/H₂PO₄^-,Cl^-and Br^-)and two concentrations of HA can impact on the photocatalytic degradation rate and degradation rate of BZF and CPF in NF-TNTAs.Only Br^-can promote the degradation of the two drugs,while other water-soluble substances can inhibit the degradation of the two drugs at various levels.