Removal Of Ciprofloxacin In Water By Using Iron And Manganese Mixed Catalysts

Antibiotics especially with high concentration in wastewater are difficult to biodegrade and can not be effectively removed by sewage treatment plants.Its abuse and continuous accumulation in the water environment lead to a series of environmental problems,which not only have an important impact on the microbial community,but also affect the whole ecosystem.The traditional wastewater treatment technology is not ideal for the treatment efficiency of refractory high concentration organic wastewater.Recent years,electro-Fenton（EF）technology has become a research hotspot due to its characteristics of strong universality,high efficiency,good performance and environmental friendliness.However,EF technology is often limited in practical application due to low current utilization rate and arrow p H application range thus caused its high cost.Therefore,it is of great significance to study catalytic materials with high efficiency and low energy consumption.On this study,the homogeneous ferro-manganese mixed catalyst and heterogeneous ferro-manganese mixed catalyst were prepared with ferro-manganese element as the main action component.The three conditions of ferro-manganese dosage,p H and current were optimized.The removal efficiency and current mineralization rate of ciprofloxacin（CIP）in water were analyzed.A degradation path of CIP in the process of homogeneous ferro-manganese mixed catalyst was investigated and the toxicity of the intermediate was analyzed.Surface morphology of two kinds of cathode materials was analyzed and studied.Main research conclusions are as follows:（1）By controlling three sets of variable factors,namely the molar ratio of iron and manganese,applied current,p H,determinating these optimal parameter values to CIP removal efficiency and the total organic carbon（TOC）removal efficiency,respectively,namely:when the applied current is 400 m A,Mn²⁺/Fe²⁺molar ratio is 2:1,p H=3,the initial concentration of 50 mg/L of CIP removal rate and the TOC removal efficiency is the highest,respectively in 30 min reached95.62%and 94.00%in 8 h;The hydrazine hydrate is used to modify the cathode and its surface morphology has been detected by scanning electron microscope（SEM）,and the results indicate that the modified graphite felt（MGF）surface formed irregular carbon nanoparticles,and these fold and irregular carbon nanoparticles in alcohol solution with hydrazine hydrate formed sediment nitrogen functional groups in the heating process and thus increase the gas-liquid contact angle,and the CIP remove efficiency of MGF is better than unmodified cathode.Moreover,the energy consumption of the system was calculated and analyzed.The high current mineralization rate（MCE,%）and the total organic carbon removal rate of CIP with the initial concentration of 50mg/L were both stable above 90.00%after repeated use,indicating that the cathode was characterized by high efficiency and durability.By introducing the acid mine wastewater（AMD）rich in iron and manganese into the EF system,the removal efficiency of CIP with the initial concentration of 50mg/L was the highest after the 20-times dilution of the AMD,and reached 89.00%after 60min.（2）11 CIP intermediates generated in degradation processes were determined by high performance liquid chromatography-mass spectrometry（HPLC-MS）,which were A（m/z=330）,B（m/z=264）,C（m/z=364）,D（m/z=262）,E（m/z=296）,F（m/z=362）,G（m/z=294）,H（m/z=310）,I（m/z=270）,J（m/z=286）and K（m/z=143）,respectively.According to the property and structure of CIP and the law of hydroxyl radical action,a relatively complete potential degradation path of CIP was proposed.The toxicity values of 11 intermediates during the EF of CIP degradation were calculated according to quantitative structure-activity relationship,（QSAR）.The intermediate K（m/z=143）was highly toxic,and was highly responsive to the chronic and acute toxicity values of aquatic organisms such as fish,daphnia and algae.（3）By controlling three sets of variable factors,namely dual iron manganese oxide（FMBO）dosing quantity,impressed current intensity,and p H to determinate and calculate the effect of different parameter values to CIP removal rate,respectively.And get the optimal parameters,namely:in 300 mg FMBO dosing quantity,p H=3,when the current value of 100 m A to the initial concentration of 25 mg/L removal efficiency of CIP,reached 92.48%in 30 min.Based on the obtained optimal conditions,the TOC removal efficiency and mineralization current rate（MCE,%）of CIP under the optimal conditions were determined and calculated,which were 93.77%and 20.26%,respectively,and which were 44.77%and 10.55%higher than that of the unmodified cathode,indicating that the FMBO modified graphite felt cathode（FMBO/GF）had good catalytic performance and catalytic efficiency.The surface morphology of FMBO/GF is obtained by SEM,analysis that modify the cathode surface formed many particles of nanoscale connections,these irregular nanoparticles in the modification in the heating process increases the specific surface area of the cathode,the H₂O₂ production increase,the modified cathode compared with the unmodified cathode to CIP removal efficiency is better.The linear sweep voltammetry（LSV）was measured for four groups of modified cathodes with different FMBO additions.The results showed that the current response value was the highest and the unmodified cathodes the lowest when the FMBO addition amount was300mg.In other words,the optimal FMBO addition amount of the cathode was determined to be 300mg again,and the electrochemical performance was much higher than that of the unmodified cathodes.