Degradation And Bioaugmentation Mechanisms Of Sulfonamides By Microbial Fuel Cell

Excessive use or long-term abuse of antibiotics will pose a huge potential threat to the environmental ecosystem,and the environmental residues and ecotoxicological effects of antibiotics have become one of the major environmental problems worldwide,so antibiotic treatment technologies are becoming more and more widespread to follow.As a new type of wastewater treatment technology and power source technology,microbial fuel cell(microbial fuel cell,MFC)has become one of the hot research topics in the environmental field at home and abroad in recent years.In this paper,the iron-reducing bacterium Shewanella putrefaciens(Shewanella putrefaciens)was used as an electrically active microorganism to study the degradation and transformation effects of MFC on two sulfa antibiotics Sulfamonomethoxine(SMM)and Sulfadiazine(SDZ).Investigate the effects of different electrode materials,environmental factors,and different electron donors on the electricity production of MFCs and the degradation of antibiotics,and further optimize and model the degradation conditions.The research results provide a way to improve the electricity production performance of MFCs while achieving the degradation of antibiotics Theoretical basis.The main research contents and results are as follows:1)A two-chamber microbial fuel cell with a three-electrode system was constructed.The degradation kinetics and electrochemical characteristics of two typical sulfonamide antibiotics(SMM,SDZ)by MFC were investigated,and the degradation mechanism of the two typical sulfonamide antibiotics by MFC was preliminarily discussed.The results show that under the same antibiotic concentration,the anode surface protein and riboflavin concentration in the MFCs solution with SMM as the substrate are higher than SDZ,which proves that the MFCs system under the condition of adding SMM has stronger electricity generating capacity than SDZ.LC-MS was used to determine the intermediate products that degrade SMM and SDZ in the MFCs system,and two degradation pathways of SAs antibiotics were speculated.SMM can be degraded in the MFC system in two ways:SMM is oxidized by·OH in the MFC system to produce intermediate products(P296)and(P326);SMM can be degraded in the MFCs system and the electron transfer of anode microorganisms and the reduction of H~+The intermediate product(P282)is formed,and then(P284)is further formed.SDZ is mainly hydrolyzed in the MFC system.There are also two pathways.One of the pathways connects the N-H bond of the pyrimidine moiety to be hydrolyzed to generate p-aminobenzenesulfonic acid,the reduction of sulfonamide partial sulfur is followed by the formation of p-aminobenzene sulfonic acid.Another way is that the N-S bond is attacked by·OH,and the two parts of SDZ are separated from the sulfonamide part and the pyrimidine part to generate 2-aminopyrimidine and p-aminobenzenesulfonic acid.2)The experiment takes SMM as the research object,and uses the method of MFCs system to degrade SMM,and investigates the degradation and electricity generation performance of SMM by different electrode materials,different p H and different substrates.The results show that the three anode materials have improved the power generation capacity of MFCs.The degradation rate of MFCs to SMM and the degradation of MFCs and the performance of electricity generation are all:carbon felt>carbon paper>graphite rod;MFCs system has the best electricity generation ability in the range of p H 6.0～7.0,and degradation in the range of p H 7.0～8.0 the highest efficiency;when using four different substrates(lactic acid,acetic acid,propionic acid,glucose)as the dual-chamber MFC of the SMM monitoring biosensor for degradation and electricity generation research.Under the condition of 30℃,the concentration of SMM with sodium lactate as substrate is 10 mg/L,the electrochemical activity of MFC is the best,the maximum output voltage is 899.17m V,the maximum output power density is 152.57 m W/m~2,and the internal resistance is about 948.27Ω,when the concentration of sodium propionate as the substrate of sulfamethoxine is 30 mg/L,the minimum output voltage is 81 m V,the power density is:1.17 m W/m~2,and the internal resistance is 1466.73Ω.By comparing the degradation rate of SMM of different substrates,when the SMM concentration is 10mg/L,the corresponding degradation rates of sodium lactate,sodium acetate,glucose,and sodium propionate are:60.08%,58.21%,49.77%and 31.42%.The above conclusions conclude that sodium lactate has the strongest power generation and degradation performance of the four substrates.3)Compare the degradation analysis of SMM by different electron donors.By adding different concentrations of humic acid(HA)to simulate humus in natural waters,and comparing electron inhibitors(rotenone,N-acetyl-L-methionine),the effects of degradation of SMM and electricity generation in the MFC system were investigated.This chapter constructs two kinds of electronic shuttle MFCs(Anthraquinone-2,6-Disulfonate Sodium AQDS and Riboflavin),investigates the treatment efficiency of MFC on the pollutants in simulated antibiotic wastewater and the main influence factors,and proposes the optimal The shuttle strategy and mechanism provide a basis for the treatment efficiency of bio-enhanced antibiotic wastewater.The results showed that when HA=5.0 mg/L,the SMM removal rate reached the maximum 72.79%,and when HA was within a certain concentration range(2～5 mg/L),it would promote the degradation of SMM by MFCs.When it exceeds a certain range(10 mg/L),HA will inhibit the degradation of SMM by MFCs.The addition of the two electron transport inhibitors has a negative impact on the degradation of SMM by MFCs.Studies have found that the degradation and electricity production inhibition of rotenone is higher than that of N-acetyl-L-methionine.Comparing the degradation of the two electronic shuttles,riboflavin enhanced degradation of SMM is stronger than AQDS.Both electronic shuttles can form a biological/non-biological synergistic system with Fe(III)and the amount of Fe(II)produced by riboflavin More than AQDS.The experiment simultaneously analyzed the electron transfer capacity and electrochemical impedance spectroscopy of the two electron shuttles,and the research results of the electricity generation performance were consistent with the degradation performance.The research results provide a certain theoretical basis for the degradation and transformation of organic pollutants in the process of iron dissimilatory reduction in nature.4)Response surface methodology(RSM)and artificial neural network(BP-GA-ANN)models were used to optimize the degradation conditions(reaction time,reaction temperature,solution p H,etc.)of SMM in the MFCs system.The test fits the response surface prediction model and obtains the optimal degradation conditions:the reaction time is 79.72 h,the p H of the MFC system is 7.22,and the temperature is 29.65℃.Under these optimal conditions,the optimal degradation rate of SMM is 60.12%.Experiment to build a BP-neural network model.Taking the coefficient of determination R~2 and the mean square error MSE as the measurement indicators,the genetic algorithm is used to optimize the BP-GA-ANN model to analyze the relationship between SMM degradation and the three independent variables of temperature,p H and time,and the model is established through the global search function.The model results show that when the number of neurons is 8,the prediction effect is the best.The mean square errors of the training and testing process are MSE 0.0228 and 0.0495.The correlation coefficient R~2 value of the two models is0.98613>0.98554,which becomes a more ideal prediction model.That is,to establish structural models and regression problems between the degradation behavior of nonlinear pollutants and complex environmental factors,and simultaneously establish a neural network model optimized by genetic algorithms to indirectly predict the degradation rate of SMM and compare and analyze the results.