The Effectiveness And Mechanism Of Enhanced Oxidative Nanosized Zero-valent Copper Technologies In The Degradation Of Fluoroquinolones

Fluoroquinolone antibiotics?FQs?was a class of excellent antimicrobial agents,and they had been extensively applied to prevent or treat bacterial infections of human beings and animals.In recent years,FQs had become emerging pollutants since they were consequently detectable in wastewater,surface water,groundwater,and seawater.Wastewater containing FQs showed high stability,high toxicity,poor biodegradability,which was harm to ecological environment and human health.Advanced oxidation processes?AOPs?were a class of promising technology for wastewater treatment due to its merits such as effectiveness,universality,thoroughness.This thesis studies nanosized zero-valent copper activation of molecular oxygen and hydrogen peroxide for the degradation of FQs.The oxidation efficiency and mechanism of FQs were systematic studied.The degradation of enrfloxacin was investigated in the presence of nZVC and molecular oxygen.The effects of nZVC dosage,ENR concentration,solution pH,and temperature on ENR degradation were researched.The results showed that the removal of ENR was enhanced with the increase of nZVC dosage,hydrogen-ion amount,and temperature.The removal of 5mg/L of ENR was achieved 90.8%at 60 min when the presence of 0.5 g/L of nZVC,T=25?,and pH=3.The introduction of TBA drastically inhibited NOR degradation and the removal efficiency was only 22.2%,which demonstrated that·OH was the predominant reactive oxygen species in nZVC/Air system.In addition,the plausible catalytic mechanism in nZVC/Air system was proposed:nZVC reacted with O₂ to produce H₂O₂,Cu???,Cu???through single electron or dual electron transport mechanism,then Cu???and H₂O₂ constituted the Fenton-like system,and a large amount of·OH was created,which involved in ENR degradation.Subsequently,nZVC was used as hydrogen peroxide?H₂O₂?activator in conjunction with ultrasonic irradiation?US?for the oxidative degradation of norfloxacin?NOR?.Compared with silent degradation system,a significantly enhanced NOR removal was obtained in sono-advanced Fenton process.The effects of nZVC dosage,H₂O₂concentration,ultrasound power,solution pH,inorganic anions and dissolved gas on NOR degradation were researched.The results showed that the removal of NOR was enhanced with the increase of nZVC dosage,H₂O₂ concentration,ultrasound power,and hydrogen-ion amount.Moreover,the inhibitory effect of different inorganic anions on NOR degradation followed the sequence of SO₄^2-?NO₃^-?no salt?Cl^-?HCO₃^-.Continuously passing oxygen or nitrogen into the US/nZVC/H₂O₂ system would inhibit the degradation of NOR.The removal of 5mg/L of NOR was achieved 91.5%at 30 min when when the operating conditions were 0.25g/L nZVC and 20 mM H₂O₂ with ultrasound power of 240 W at 20 kHz.According to the radical quenching experiments and electron paramagnetic resonance technique,hydroxyl radicals in solution(·OH_free)were verified as the primary reactive species,and superoxide anion radicals?·O₂^-?were regarded as the mediator for the copper cycling by reduction of Cu???to Cu???.The synergistic effect between US and H₂O₂ would promote the release of Cu???,then Cu???and H₂O₂ constituted the Fenton-like system,and a large amount of·OH was created,which involved in NOR degradation.The oxidation of NOR mainly occurred by cleavage of the piperazine ring,transformation of the quinolone group,hydroxylation of the quinolone and benzene ring,defluorination of the benzene ring,respectively.