Development Of Streptococcus Sanguis-driven Fe^?-TAML/H₂O₂ Systems To Remove 4-CP In Water

Iron(?)-tetraamidomacrocyclic ligand(Fe^?-TAML)activator able to activating H₂O₂ is an environmentally friendly catalyst.It has been widely studied in different fields due to its selectivity and high catalytic activity.In the chemical oxidation process,there are many concerns about excessive losses and potential hazard of H₂O₂ in the transportation,handling and storage.In the commen in-situ synthesis of H₂O₂,there are many concerns about low catalytic efficiency,high cost,highly explosive and complex processing technology.Microbial synthesis of H₂O₂ has been widely concerned in the study of environmental pollution control for the advantage of the mild reaction conditions and simple process.Meanwhile,S.sanguis is a beneficial oral symbiotic bacterium.They produce H₂O₂ to antagonize suspected pathogens.Therefore,the purpose of this paper is to construct Fe^?-TAML/H₂O₂ degradation system driven by S.sanguis.P-chlorophenol has been selected as target pollutant and the related factors of S.sanguis and the degradation system were studied and the application methods was included.Through the analysis of the growth curve of S.sanguis and the initial rates of H₂O₂ under various influencing factors,it can be obtained that S.sanguis could not grow under the environment below 20? or pH 9.It had no toxic effect on S.sanguis under the Fe^?-TAML concentration of 30 ?mol/L.The initial rates of H₂O₂ of S.sanguis were initially increased and subsequently decreased with increasing temperature,and the maximum initial rates of H₂O₂ was 1.861 nmol H₂O₂/min×107 cells at 30?.The initial rate of H₂O₂ of S.sanguis was the maximum at pH 7(1.5 nmol H₂O₂/min × 107cells).There was no significant difference at other pH conditions.The initial rate of H₂O₂ under full oscillation condition was about 1.7 times that under static culture condition.It can be concluded that S.sanguis has a high initial production rate of H₂O₂ under the conditions of 20?40?,pH 6?8.5 and full oscillation.The related factors affecting the degradation activity of p-chlorophenol in Fe^?-TAML/H₂O₂ system driven by S.sanguis were analyzed.The results showed that:the degradation efficiency of p-chlorophenol increased with the increase of temperature,the degradation rate constant of p-chlorophenol increased from 0.170 h-1(15?)to 0.900 h-1(30?).There was a positive linear correlation between the degradation rate constant of p-chlorophenol and the cell density of S.sanguis(OD600=0.05?0.8).The removal rate of p-chlorophenol within 3 h was initially increased and subsequently decreased with increasing pH(6?9)and Fe^?-TAML concentration.P-chlorophenol can be degraded continuously at pH 8 The degradation rate of p-chlorophenol was 0.541 h"1.The degradation rate constant of p-chlorophenol increased from 0.258 h"1 to 0.803 h"1 with the increasing Fe^?-TAML concentration(0.5?2 ?mol/L).High removal of 97%was achieved forp-chlorophenol in water within 3 h under the optimized conditions,including reaction temperature of 25?,pH 8,Fe^?-TAML of 2 ?mol/L and OD600 of 0.4.And this system can reduce the dependence on exogenous H₂O₂.Finally,S.sanguis was immobilized by sodium alginate to optimize the main process parameters under the above reaction conditions,and the stability under different pH conditions and reusability of the immobilized cells were evaluated.The optimized technological parameters were as follows:sodium alginate 1%,calcium chloride 1%,crosslinking time 1 h,cell density of S.sanguis is 6×109 CFU/(mL sodium alginate).Under these conditions,the pellets were uniform,regular and had certain mechanical strength,and the degradation rate constant of p-chlorophenol was the maximum(0.529 h-1).Compared with the free bacterial system,the immobilized pellets system can continuously degrade p-chlorophenol at pH 9,indicating that it has stronger pH adaptability.After 10 cycles,it was found that about 66%of p-chlorophenol can still be removed by immobilized pellets...