Degradation Of Several Antibiotics In Water Environment Based On Advanced Oxidation Using Persulfate

Fluoroquinolones（FQs）and sulfonamides（SAs）antibiotics are representative and widely used antibiotics,their production wastewater and residues in the use process permeate into the water environment by surface runoff and soil infiltration caused unpredictable harm to the ecological environment and human health,it was an urgent problem to develop efficient technology to remove FQs and SAs from water environment.In this paper,enoxacin（ENO）and sulfathiazole（STZ）were taken as research objects,and the degradation kinetics,influencing factors,degradation intermediates and possible degradation pathways of ENO and STZ were systematically studied by using advanced oxidation technology of ultraviolet（UV）or heat-activated potassium persulfate.In addition,the application effect of advanced oxidation technology of potassium persulfate on other FQs was also explored.The main contents and conclusions are as follows:ENO of the degradation kinetics,influencing factors and degradation pathways in UV/PS system,were studied experimentally and theoretically.The effects of PS dosage,initial p H of solution and inorganic ions in water on the removal efficiency of ENO were investigated.The research results indicate that ENO is almost completely removed after12 minutes of UV irradiation under optimized experimental conditions（[ENO]₀=0.0312m M,[PS]₀=1.560 m M,[p H]₀=7.0±0.1）.In the range of 0～1.56 m M,the degradation efficiency of ENO increases with the increase of PS concentration.Acidic and neutral conditions are more conducive to the degradation of ENO.And CO₃^2-and HCO₃^-had obvious inhibitory effect on the degradation of ENO,while Cl^-and H₂PO₄^-only had negligible influence.The identification of active species showed that in UV/PS system,hydroxyl radical（^·OH）was the main active component for ENO degradation.Based on degradation intermediates detected by high performance liquid chromatography and mass spectrometry（LC/MS）technology and density functional theory calculation of degradation mechanisms,the main degradation pathways of ENO were predicted.It was suggested that piperazine ring fracture is the main degradation pathway of ENO in its early degradation stage.The theory calculation results showed that the electron transfer reactions between SO₄^·-or^·OH and ENO are difficult to occur thermody namically and kinetically,and the reactivity of sulfate radical(SO₄^·-)in ENO degradation was higher than that of^·OH.Moreover,in the degradation experiment of ENO in actual water samples,it was found that the degradation efficiency of ENO in tap water and shihe river water was close to 90%after 12 min of light.The other four representative FQs in synthetic wastewater also showed high degradation rate after 20 min illumination,among which the degradation rate of Marbofloxacin was 88%.This study provides new ideas and reference value for the effective removal of ENO and other FQs in wastewater by UV activated PS technology.（2）The kinetics,influencing factors and degradation pathways of STZ degradation by thermal-activated PS were systematically studied,and the effects of PS dose,reaction temperature,initial p H,inorganic ions on STZ degradation were investigated.The results showed that the degradation efficiency of STZ increased with the increase of PS dosage and reaction temperature.The degradation reaction conforms to the apparent first-order kinetic model,and the apparent activation energy（Ea）is 64.10 k J mol^-1.The degradation rate of STZ decreased gradually with the increase of initial solution p H,and at[p H]₀=3±0.1 the degradation efficiency reached the highest value of 80.65%after the reaction of240 min.Both anions(Cl^-,SO₄^2-,CO₃^2-,HPO₄^2-)and cations(K⁺,Na⁺,Ca²⁺,Mg²⁺)in solution had inhibitory effect on the degradation of STZ.The quenching results showed that both^·OH and SO₄^·-play an important for degradation of STZ.A total of eight degradation intermediates of STZ were identified by LC/MS technique,and six possible degradation pathways were deduced including hydroxylation,SO₂removal,-NH₂group oxidation or^·OH replacement,N-C and N-S bond disconnection.Moreover,the toxicity of STZ and its intermediates to three aquatic organisms（fish,flea,green algae）was predicted by ECOSAR program based on quantitative structural activity relationship model,the results showed that STZ and its degradation intermediates had certain toxicity to the three aquatic organisms.This study can provide a scientific basis for the removal of sulfonamides from water by thermal activated persulfate technology.