Mechanism And Application Of Tetracycline Antibiotics Pollutants Removal By Carbon Based Nano Microelectrolysis Materials

In recent years,because of the rapid increase in the number of drug-resistant pathogens and symbiotic bacteria in the world,the extensive use of antibiotics and their pollution of waterbody have aroused the public's attention.Among them,tetracycline antibiotics?TCs?,which are used in large-scale livestock and aquaculture,perform well in antibacterial activity and have a low cost,resulting in being one of the most widely used antibiotics.Because of the specificity of antibiotics,it is difficult for the residual TCs to degrade by themselves in the natural environment.In addition,antibiotics can inhibit or destroy the growth of microorganisms,so the biodegradation rate of most TCs is much lower than their non biodegradation rate.Therefore,in the face of this dilemma,the non biological treatment method highlights the technical advantages,and it is imperative to explore the economic,efficient,and environmentally friendly treatment technology for TCs'removal.At this time,due to the high treatment efficiency and low operating cost,traditional micro-electrolysis?TME?is widely used in the treatment process of refractory pollutants.However,TME usually uses fixed bed or tower reactor.Due to the influence of the properties of iron and carbon filler particles,packing hardening and channeling often occurs after a period of stable operation,which makes the treatment efficiency drop rapidly.These problems have been restricting the further application of TME technology.In this paper,the action mechanism of microelectrolysis and the reaction process of TME are analyzed based on corrosion electrochemistry and chemical affinity.If there was depolarizer in TME reaction system,it can trigger TME reaction.In addition,pH and O₂ determined whether TME reaction can proceed smoothly.The chemical affinity of TME provided the driving force for TME reaction.The larger the driving force,the higher the reaction rate and the better the treatment effect.The Fe/C?area ratio?and particle size of the filler had an important influence on the TME treatment effect.Based on the analysis above,the nanomaterials of ACF-nMET,CF-nMET,AC-nMET,and Cu-nMET were prepared in view of the hot issue of water pollution caused by TCs.ACF-nMET and CF-nMET can be used in fixed-bed reactors while AC-nMET,Cu-nMET were used in fluidized bed reactors.The effectiveness and mechanism of processing TCs in fixed bed reactors and newly constructed fluidized bed reactors with different materials prepared by experiments were examined experimentally to solve the engineering problems of easy micro-electrolytic material compaction and channel flow.Improving the combination form of anode and cathode materials is an important way to solve the problems of TME materials such as bonding and channeling.With the improved reduction method,combined with the porous skeleton and recyclability of activated carbon fiber?ACF?and foam copper?CF?,nano micro-electrolysis materials ACF-nMET and CF-nMET for fixed bed reactors were prepared.The porous structure and recyclable property of ACF-nMET and CF-nMET solved the sintering and channeling problem of micro-electrolytic material.Meanwhile,ACF-nMET supported Ag as catalyst,and CF in CF-nMET was both a cathode material and a good catalyst,which improved the efficiency of removing pollutants.The batch test results showed that the treatment efficiency of ACF-nMET and CF-nMET to OTC and DC of TCs was92.1%and 99.2%respectively,and the removal efficiency of TOC was 61.2%and 58.1%respectively.At the same time,the performance of ACF-nMET and CF-nMET in fixed bed reactor was investigated.Because of the high specific surface area of nZVI and the excellent electronic transmitting performance of ACF,the average removal rate of OTC by ACF-nMET in 40-110 h was 69.2%,18.7%higher than that of TME.Moreover,as a copper material,CF can also catalyze the micro-electrolysis reaction efficiently and accelerate the removal efficiency of pollutants.The average removal rate of CF-nMET in 40-110 h was 75.8%,25.3%higher than TME and 6.6%higher than ACF-nMET.Solving the fluidization state of micro-electrolysis materials was the fundamental way to solve the problems of micro-electrolysis materials,such as plate,channel and so on.Based on different textures of powdered activated carbon?PAC?,AC-nMET,a kind of nano micro-electrolysis material for fluidized bed reactor,and Cu-nMET,which used copper as catalyst,were prepared.Due to the limitation of material density and synthesis method,it is difficult to fluidize TME packing by hydraulic action.The microscopic observation and model simulation of AC-nMET and Cu-nMET show that it not only has the characteristics of TME,but also has the characteristics of nano particles.Therefore,the reaction activity is high and the density is low,and it can be fluidized by hydraulic action,which fundamentally solves the problem of micro-electrolysis packing being easily solidified and channeled.The batch test results showed that the treatment efficiency of AC-nMET and Cu-nMET to DC and CTC was98.8%and 99.1%respectively,and the removal efficiency of TOC was 70.9%and 70.7%respectively.The kinetic study showed that the degradation kinetics of AC-nMET and Cu-nMET for DC and CTC follow a two-constant model.According to HPLC-MS,the degradation products of DC and CTC were determined,and the degradation mechanism of DC and CTC was proposed respectively.The experimental results of an experimental-scale fluidized bed?ESFB?show that it is feasible to treat pollutants with nanoparticles in the fluidized bed.The nano micro-electrolytic fluidized bed system constructed in this paper can effectively remove TCs pollutants in water and can avoid the phenomenon of filler sintering and channeling that often occur in the traditional TME reaction process.At the same time,the material utilization rate is high and the production cost is low.It has certain guiding significance for the application in the treatment of practically difficult biodegradable pollutants.