Study On Removal Performance Of Tetracycline Hydrochloride Wastewater Based On Micro-nano Bubble Synergistic Technology

In recent years,with the rapid development of industrialization,the environmental problems of water pollution have become increasingly prominent.Among them,the treatment of antibiotic wastewater has become a research hotspot in the environmental field at home and abroad.Micro-nano bubbles（MB）have the characteristics of long residence time,large specific surface area,high interface zeta potential,high mass transfer efficiency,generation of free radicals,self-pressurization and dissolution,etc,which have attracted widespread attention.This study proposes that micro-nano bubbles cooperate with iron-carbon micro-electrolysis and hydrogen peroxide technology to degrade tetracycline hydrochloride（TC）wastewater,and the combination of micro-nano bubbles/iron-carbon micro-electrolysis-H₂O₂technology to treat actual pharmaceutical wastewater,it hopes to provide a new solution for the treatment of organic wastewater.Mainly carry out the following work:（1）Using micro-nano bubbles and iron-carbon micro-electrolysis technology to treat tetracycline hydrochloride wastewater,the structure of the iron-carbon materials before and after the reaction was characterized by XRD,FT-IR,BET,SEM,EDS;In addition,different reaction times,iron-carbon dosages were studied.The influence of dosage,p H,and air intake of micro-nano bubbles on the removal rate of tetracycline hydrochloride.The results show that the micro-nano bubbles have a significant synergistic effect on the iron-carbon micro-electrolysis,when the reaction time was 120 min,the iron-carbon dosage was 100 g·L^-1,the p H=3,and the micro-nano bubble air intake was 30 m L·min^-1,the degradation rate of tetracycline hydrochloride at a concentration of 20 mg·L^-1was80.84%,and the TOC removal rate was 47.89%,The kinetic study and analysis showed that the degradation process of TC conforms to the pseudo first-order reaction kinetic model.The possible intermediate products of TC were identified by HPLC-MS technology,and the degradation mechanism of TC was analyzed.The results showed that the TC molecule was degraded into small intermediates mainly through demethylation and carbon-carbon single bond cleavage,and finally decomposed into inorganic compounds such as CO₂and H₂O.（2）Using micro-nano bubbles and H₂O₂technology to treat tetracycline hydrochloride wastewater,the degradation performance of the MB/H₂O₂system under different influencing factors was studied.The results show that when the reaction time was 150 min,the dosage of H₂O₂was 30 mmol·L^-1,the p H=3,and the MB inlet volume was 30m L·min^-1,the degradation rate of TC can reach 92.43%.The kinetic study and analysis show that the degradation process of TC conforms to the pseudo first-order reaction kinetic model.The results of response surface experiments show that the order of the primary and secondary factors affecting the degradation of tetracycline hydrochloride was:p H>H₂O₂dosage>MB air intake,and the interaction between the factors was significant.The optimal process conditions obtained by response surface method are:H₂O₂dosage was31.18 mmol·L^-1,p H was 3.0,MB inlet volume was 29.45 m L·min^-1,and the TC removal rate under this working condition is predicted to be 88.03%.Three parallel experiments were performed under the optimal process conditions.The measured TC removal rate was89.62%,which was 1.90%deviation from the theoretical prediction value,and the relative standard deviation RSD=2.68%,indicating the optimal process parameters obtained by the response surface method.It was reproducible and the model has high credibility.In addition,free radical quenching experiments and electron spin resonance（ESR）experiments show that·OH、HO₂·/·O₂^-were the main active oxygen free radicals in the MB/H₂O₂system.The possible intermediate products of TC were identified by HPLC-MS technology,and the degradation mechanism of TC was analyzed.The results showed that·OH and HO₂·/·O₂^-radicals would first attack the tetracycline hydrochloride molecule,leading to its demethylation and hydroxylation,ring-opening reaction,isomerization,deethylation,deacylation,deamination and dehydration reactions,intermediates such as m/z=141,m/z=126,m/z=110,m/z=84 are finally transformed and decomposed into inorganic compounds such as CO₂and H₂O under the action of·OH and HO₂·/·O₂^-free radicals.（3）The actual pharmaceutical wastewater was treated with micro-nano bubbles and iron-carbon micro-electrolysis-H₂O₂technology.The research results showed that when the reaction time was 240 min,the iron-carbon dosage was 200 g·L^-1,and the H₂O₂dosage was 15 m L/L,the removal rates of COD and TOC were 43.35%and 31.53%respectively,its removal efficiency was higher than other systems.The MB/iron-carbon micro-electrolysis-H₂O₂process not only gave full play to the characteristics of micro-nano bubbles,but also significantly improved the degradation efficiency of pharmaceutical wastewater.This research work provided a new idea for the treatment of actual pharmaceutical wastewater in the future.