The Study On Degradation Antibiotics In Water By UV/Persulfate

Antibiotics are widely used in medical care and animal husbandry in recent years,due to the metabolism of antibiotics in human and animals is limited and the degradation of antibiotics in conventional waste water treatment processes is also restricted,thus antibiotics could be detected in surface water frequently.The biotoxicity of antibiotics and their metabolites is high,hence the existence of antibiotics in environment would reduce microbial diversity,inhibit the growth of aquatic animals and plants and threat the balance of ecosystem.So the newly water treatment technology that can efficiently degrade antibiotics is attracting more and more attention from researchers.UV/Persulfate is a new kind of advanced oxidation processes（AOPs）based on sulfate radical（SO₄^-·）.The redox potential of SO₄^-·is high（E₀=2.60 V）and its suitable pH range is wide,hence can degrade various organic pollutants efficiently,such as dyes,pesticides,medicines and so on.The investigation of antibiotics degradation by UV/Persulfate can provide theoretical guidance for the prevention and control of antibiotic pollution and water quality safety in water environment.Under the laboratory condition,determined the more applicable persulfate;studied the degradation kinetics of NOR and OTC in UV and UV/Peroxydisulfate（PDS）systems;investigated the effects of antibiotic initial concentration,PDS dosage,pH value,dissolved organic matter（DOM）,inorganic anions and natural waters.We also analyzed the degradation products of NOR and OTC and proposed the degradation pathways of NOR and OTC.Meanwhile,we compared the changes of pH and TOC during the degradation of NOR and OTC.The main conclusions are as follows:（1）Selection of applicable persulfateWe compared the degradation of NOR in UV/PDS and UV/Potassiummonopersulfate Composite Salts（Oxone）systems.The results showed that the degradation of NOR was faster and initial loss was smaller in UV/PDS system.Thus,we selected UV/PDS system for further research.（2）The degradation kinetics of NOR and OTC in UV and UV/PDS system NOR and OTC could be degraded in UV system,and the degradation of NOR was faster.In UV/PDS system,the degradation of NOR and OTC was promoted,and within the estimated range in this study(5¹00μmol·L^-1),the greater the amount of PDS dosage,the faster the degradation of NOR and OTC.The degradation process of NOR and OTC in UV and UV/PDS systems all obeyed to the pseudo-first-order kinetic equation.（3）The effects of environmental factors on the degradation of NOR and OTC in UV and UV/PDS systemIn UV system,the degradation rate of NOR and OTC decreased with increasing its concentration;acidic condition inhibited the degradation of NOR,basic condition promoted the degradation of NOR,while acidic and basic condition both promoted the degradation of OTC.The rate of NOR degradation in surface water（SW）was almost the same as that in ultrapure water（UW）,while the rate of OTC degradation in SW was higher.In UV/PDS system,neutral condition contributed to the degradation of NOR,both acidic and basic condition inhibited the degradation of NOR and OTC,and the inhibition effect was more obvious in basic condition.The existence of DOM inhibited the degradation of NOR and OTC,and the inhibition effect was more significant with increasing its concentration.The effect of inorganic anions on degradation of NOR and OTC were quite unnoticeable.And the degradation of NOR and OTC in UW were faster.（4）The degradation products and pathways of NOR and OTC in UV and UV/PDS systemThe piperazinyl ring and quinolone ring of NOR are easily to be degraded.In UV system,NOR degraded and produced five products which were m/z 246,274,290,318 and 368.In UV/PDS system,besides the above products,piperazinyl ring and quinolone ring further cracked and produced product m/z 227.OTC is prone to experience deamination,dehydration and ring opening.In UV system,OTC degraded and produced three products which were m/z 413,426 and453.In UV/PDS system,besides the above products,m/z 380 and m/z 159 were also the degradation products of OTC.We found that under the effect of SO₄^-·,m/z 413might further go through deamination and dehydration and produced m/z 380.Meanwhile in UV/PDS system,the chemical bonds between the central two benzene rings in tetracene skeleton might be broken and produced product m/z 159.What’s more,we found OTC degradation products with m/z 246,m/z 274 and m/z 302 in UV and UV/PDS system,while their definite structures and degradation pathways couldn’t be confirmed at present,further study was still needed.（5）The changes of pH and TOC during the degradation of NOR and OTCIn UV and UV/PDS systems,the pH value of reaction system decreased with the degradation of NOR.While as for OTC,the pH value of reaction system increased in UV system and decreased in UV/PDS system.In UV system,the TOC changes were not obvious;while in UV/PDS system,the TOC decreased definitely with the degradation of NOR and OTC,when the reaction time was 60 min,we found the mineralization degree of NOR and OTC reached40.0%and 28.6%,respectively.