Experimental Study On Photochemical Conversion And Degradation Methods Of Several Typical Antibiotics

The health of humans and other living organisms is effectively protected by the widespread use of antibiotics.But because of the lack of awareness of antibiotics,the abuse of antibiotics has led to the"pseudo persistent"pollution of antibiotics in the water environment and most of the city's sewage treatment plants are unable to effectively remove trace amounts of antibiotics,which has caused serious harm to the ecological environment and human health.Photolysis is one of the most important non-biodegradable pathways in the environment.It is also an important way to reduce the concentration of antibiotics in the surface water,and the photolysis of antibiotics in natural water is usually affected by the properties of light and aqueous solution.At present,antibiotic pollutants are widely concerned.There are also have a lot of studies on photolysis of antibiotics.But because there are many kinds of antibiotics and many environmental factors affecting the photolysis.Therefore,the understanding of the environmental fate of antibiotics in the aquatic environment is still inadequate,especially in the study of the influential factors of environmental factors on the photolysis of antibiotics.In this paper,four classes?amide,quinolone and tetracycline?,a total of 5 kinds of typical antibiotics?thiamphenicol,chloramphenicol,sarafloxacin hydrochloride,enrofloxacin and oxytetracycline?were selected as the research object.The photolysis of five antibiotics in pure water,effects of single factor on photolysis of five antibiotics in water environment,effects of two factors on photolysis of thiamphenicol in water environment and effects of mixed cellulose microporous membrane as a new photocatalytic material on photolysis of thiamphenicol were analyzed and the following conclusions were obtained:?1?In the simulated light source??>290nm?irradiation,thiamphenicol does not occur direct photolysis.Chloramphenicol,enrofloxacin,sarafloxacin hydrochloride and oxytetracycline can occur direct photolysis in the simulated light source irradiation.The contribution of the spectral interval to chloramphenicol,salafloxacin hydrochloride,enfloxacin and oxytetracycline photolysis is UVA>UVB>Vis.?2?Different environmental factors have different effects on different types of antibiotics.NO₃^-,Cl^-and CO₃^2-have the same effect on the photolysis of 5 antibiotics.SO₄^2-and Mg²⁺have the same effect on the photolysis of 5 antibiotics.Besides oxytetracycline,NO₃^-,Cl^-and CO₃^2-can promote the rest 4 kinds of photolysis of antibiotics,respectively.SO₄^2-and Mg²⁺can promote the photolysis of thiamphenicol,chloramphenicol and enrofloxacin and inhibit the photolysis of sarafloxacin hydrochloride and oxytetracycline.In addition to chloramphenicol,Fe²⁺can promote the photolysis of the other 4 antibiotics.5 kinds of antibiotics were inhibited by DOM except enrofloxacin.DOM is the most effective inhibitor of 5 kinds of antibiotics.?3?Eight kinds of environmental factors can promote the photolysis of enfufloxacin in water,and only Fe²⁺can promote the photolysis of oxytetracycline.?4?The effect of two factors on the photolysis of thiamphenicol is more complicated than that of single factor.In addition to DOM and NO₃^-combination,the other five combinations have obvious complex effect on the photolysis of thiamphenicol.?5?Under double factor conditions,the conditions conducive to thiamphenicol photolysis are:high concentrations of H₂O₂ are combined with low concentrations of DOM or low concentrations of NO₃^-;when Fe²⁺is a low concentration and high concentration,H₂O₂ and NO₃^-are high concentrations;high concentration of DOM and high concentration of Fe²⁺;low concentration of DOM and high concentration of NO₃^-.?6?The mixed cellulose microporous membrane in the light can produce hydroxyl radicals to thiamphenicol degradation in pure water,the actual surface water and sewage.The material that produces hydroxyl radicals under light is cellulose nitrate.Under light,the nitrocellulose groups in the cellulose nitrate have changed continuously,and this may lead to the production of hydroxyl radicals.Membrane area,light intensity,temperature increase and pH reduction are beneficial to the mixed cellulose microporous membrane to produce more hydroxyl radicals,so that the photodegradation rate of thiamphenicol increased.Mixed cellulose microporous membrane does not require O₂ when it is used for the photodegradation of thiamphenicol.It can be reused and the ability of its photolytic thiamphenicol did not weaken.With the increase of illumination time,the mixed cellulose membrane is more and more easily to break.?7?The mechanism of the degradation of thiamphenicol was initially established.That is,the negative charge distributed near the benzene ring in the thiamphenicol molecule could be attracted to the positive charge of nitrogen in the nitro group of the mixed cellulose microporous membrane.And the benzene ring of thiamphenicol as a flat surface in the film surface,reducing the distance between the benzene ring and the membrane,more conducive to the benzene ring plus four hydroxyl.