| With the development of the economy and technology,industry,pharmaceuticals,and breeding have flourished.However,a series of pollution problems have ensued.Endocrine disruptors（EDCs）,represented by 17beta-estradiol（E2）,are widely detected in the aqueous environment,and because they can cause serious effects on the health and reproductive systems of humans and aquatic organisms,there is a need to find a green,effective and low-cost method to remove EDCs.In recent years,biotechnology has been used to remove EDCs,this method has the advantages of high removal efficiency,low-cost,simple operation,and degradation products are environmentally friendly.But traditional free cells had been inhibited by environmental adverse factors in the removal process,and microorganisms were poisoned by contaminants.Microbial immobilization technology can provide stable growth and metabolic environment for microorganisms,the density and metabolic performance of microorganisms were improved.Therefore,in this study,a strain of E2-degrading bacteria was isolated from activated sludge,and reduced graphene oxide（rGO）was prepared from green tea extract as an immobilization carrier to synthesize a biocomposite（FJ1@rGO）for the removal of E2 from water.In this study,a strain of E2-degrading bacteria was isolated from activated sludge and named Ochrobactrum sp.FJ1,after physiological and biochemical detection and 16S r RNA sequencing analysis.Strain FJ1 degraded 97.65%of E2(15 mg·L-1).In addition,E2removal was inhibited when an additional carbon source was added.SEM and FTIR analyses revealed that strain FJ1 had a stress response in the presence of E2,short of the strain length and folds that appeared on the surface,and functional groups such as proteins,lipids,and polysaccharides on the bacteria played a role in the removal process.The degradation products of E2 were analyzed by LC/Q-TOF-MS,the results demonstrated that the main degradation products of E2 were estrone（E1）and 4,6-OH-E1,which were further degraded to other metabolites by strain FJ1.Based on the previous research of our group,rGO was synthesized by green tea extract,and the novel biocomposite（FJ1@rGO）was synthesized by immobilizing strain FJ1 onto rGO for the removal of E2.The materials were characterized by SEM-EDS,Raman,and FTIR,and it was confirmed that FJ1@rGO was successfully prepared.The removal rate of E2 by FJ1@rGO was enhanced by 20%to compared with that of free cell,reached 85.00%.Response surface modeling was used to optimize the preparation conditions of FJ1@rGO,and the optimal conditions were calculated as 19.5 h fixation time,4.4%inoculum,and0.34 g·L-1 rGO dosage,and the optimized FJ1@rGO improved the removal efficiency of E2 by 8.72%to 93.72%.The effect of FJ1@rGO on the removal of E2 at different temperatures,initial concentrations,and dosing amounts was investigated,and the results showed that the removal rate reached 93.72%at 30℃,and both low and high temperatures would inhibit the removal of E2.The amount of material added had the greatest effect on the removal efficiency of E2,and the removal efficiency of E2 was 85.43%when the material was added at 0.96 g·L-1.The results of degradation kinetics,adsorption kinetics,and thermodynamic calculations showed that the removal process of E2 by FJ1@rGO was following the primary kinetic model,pseudo-secondary kinetics,and the process was a synergistic effect of physical adsorption and biodegradation,and the thermodynamic results proved that the process was a spontaneous and feasible exothermic process,and the increase of temperature would reduce the adsorption amount.The characterization results of SEM,FTIR,Raman indicated that the tolerance of the immobilized strain was enhanced and the structure of FJ1@rGO is stable.According to the above experimental results,it is proved that FJ1@rGO can effectively remove E2 from water,which provides a new bioremediation technology and theoretical basis for solving E2 pollution in the environment. |
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