Degradation Of Atenolol And Carbamazepine By Ultraviolet Light Emitting Diode Combined With TiO₂ Photo Catalytic

In recent years,the wide occurrence of pharmaceuticals and personal care products(PPCPs)in natural water environment received extensive scientific interest as well as public awareness due to their potential hazardous effect on human beings and ecological system.The environmental fate of these PPCPs,including transportation and transformation,is still largely unknown up to data and traditional wastewater processes are weak in degrading new pollutants.Heterogeneous semiconductor photocatalysis with nano-TiO2 as a photocatalyst is considered as the most promising organic pollutant treatment technology.After being excited by photons with energy greater than or equal to bandgap energy,TiO2 can generate valence band holes and conduction Electrons with valence holes that directly oxidize adsorbed chemistries or selectively degrade multiple pollutants by reacting with surface-bound OH and/or adsorbed H2O molecules to produce strongly oxidizing hydroxyl radicals.Compared with the traditional UV mercury lamp,UV-LED technology have the advantages of low energy consumption,long life,simple structure,the wavelength is not the only,no secondary pollution and non-toxic mercury-free UV-LED has become the focus of the future development of UV emitters Direction of development.In this paper,Atenolol and carbamazepine were selected as the representatives of PPCPs in water.Both of them are characterized by large amount of use,strong environmental hazards,stable structure and not easily degraded.TiO2 photocatalytic degradation of PPCPs feasibility evaluation of the impact of various factors on the photocatalytic degradation of the effect of the analysis identified the degradation process intermediate products and explored the degradation reaction mechanism.The main conclusions are as follows:Atenolol can be effectively degraded by ultraviolet light emitting diode combined with TiO2 photocatalysis,and the degradation rate of ATL can reach hundred percent in 60 minutes.Atenolol cannot be degraded properly by hydrolysis,photolysis and adsorption.UV-LED wavelength of light has a greater impact on the degradation of ATL,long-wave ultraviolet light is conducive to its degradation,increase the UV-LED radiation intensity can significantly increase ATL degradation rate.The morphology of nano-TiO2 catalyst has certain influence on the degradation of ATL.Increasing the dosage of catalyst can increase the degradation rate,but there is a threshold value.When the wavelength of UV-LED was at 365nm,the light intensity was 774?W/cm2,the photocatalytic degradation of atenolol UV-LED was the best when the photocatalytic morphology of TiO2 was mixed crystal and the mass concentration was 2.0g/L.The pH value of the reaction system has a great effect on the degradation of ATL.Acidic conditions inhibit the degradation of ATL and increase the degradation rate of ATL.The degradation rate of ATL decreased with the initial concentration.Coexisting in water such as SO42-,NO3-and Cl-had little effect on the degradation of ATL.The addition of CO32-and HCO3-ions promoted the photocatalytic degradation of ATL significantly.The presence of Ca2+ and Mg2+ in water coexisted had little effect on the degradation of ATL.The presence of Cu2+strongly inhibited the degradation of ATL.The degradation rate of atenolol was accelerated significantly by adding of ferric iron.Carbamazepine can be effectively degraded by ultraviolet light emitting diode combined with TiO2 photocatalysis,and the degradation rate of CBZ can reach 98.5 percent in 60 minutes when the reaction rate constant is 0.0674 min-1 respectively.The UV-LED wavelength has a great effect on the degradation of CBZ.The degradation of UV-LED at 365nm is better than that at 275nm.Increasing the luminous intensity of UV-LED could improve the degradation rate of carbamazepine,and the best luminous intensity of CBZ was 774?W/cm2.The morphology of nano-TiO2 catalyst has certain influence on CBZ degradation.Mixed-type nano-TiO2 has been proved to be most effective for photocatalytic degradation.Within a certain range,the degradation rate of CBZ photocatalytic reaction increases with the increasing concentration of nano-TiO2.When the concentration of catalyst is up to 2.8g/L,the CBZ degradation rate continues to decrease when the catalyst dosage is increased.Acidic conditions have a certain inhibition of photocatalytic degradation,the system pH increased CBZ degradation rate was significantly improved.The degradation rate of carbamazepine decreased with the increase of the initial concentration,and the degradation reaction law was in line with the first order reaction kinetics.The co-presence of anions in the water such as Cl-ions have negligible effect on the degradation of CBZ,while SO42-and NO3-ions have some inhibition on the degradation of CBZ.On the contrary,the addition of CO32-and HCO3-ions can significantly promote the photocatalytic degradation of CBZ.The presence of cations such as Ca2+,Mg2+ and Cu2+ in water can inhibit the degradation of CBZ to a certain extent,while the presence of Fe3+ has a significant effect on the degradation of C.BZ.The addition of high concentration of tert-butanol to the reaction system can basically completely inhibit the photocatalytic degradation of CBZ,indicating that hydroxyl radicals are the main active substances for reaction degradation.The total organic carbon of photocatalytic system changes slowly.After 60 min UV-LED irradiation,the removal rate of total organic carbon were only 14.81%and 12.22%,respectively.The photocatalytic degradation reaction produced stable intermediate products.Atenolol photocatalytic degradation pathway mainly includes ether branch-breaking,mono-hydroxylation and double-hydroxylation,the formation of benzaldehyde derivatives and other forms of hydroxyl radicals most likely to attack ATL molecules instead of ether benzene ring.Carbamazepine produced many structurally similar reaction intermediates during the UV-LED photocatalytic reaction.The degradation was mainly carried out by hydroxylation reaction,hydrogenation reaction,epoxidation reaction and ring-opening reaction.Among them,the carbon-carbon Double bond is the easiest offensive position.The TOC removal rate of atenolol reaction system can reach 76.5%after keeping the UV-LED photocatalytic sustained reaction for 360 min.The TOC removal rate of the carbamazepine photocatalytic reaction system reaches 82.78%after 480 min UV-LED irradiation,most of which intermediate product can be removed by prolonged photocatalytic reaction.