Study On The Removal Of Sb From Aqueous Solutions By Fe(?) Modified Proteus Cibarius:Adsorption Optimization And Mechanism

Environmental pollution caused by excessive antimony(Sb)in the water environment is receiving more and more attention.Biological adsorption of Sb has the advantages of low cost,environmental friendliness,and easy recovery of heavy metals after adsorption.In recent years,a series of research reports on bioadsorbents have emerged,however,these bioadsorbents have the disadvantage of low adsorption capacity,and there is no research report on antimony removal by iron salt modified bacillus.Thence,this reaearch was focused on the oxidative and differential gene expression,optimized cultivation,the preparation of iron salt biosorbents(Fe(?)modified Proteus cibarius adsorbent(FMPAs))of Proteus cibarius DSHN0704,which was screened from antimony-contaminated soil by our research team in the early stage,and the adsorption optimization and mechanism were also studied.The main research results obtained are as follows.1.The oxidative characteristics and mechanism of Proteus cibarius DSHN0704 were explored.The growth characteristics and redox performance of Proteus cibarius DSHN0704were studied,in addition,no-sequence transcriptome sequencing under Sb(?)stress was performed on Proteus cibarius DSHN0704 to analyze functionally differential gene expression.The results showed that,(1)Proteus cibarius DSHN0704 has a strong ability to oxidize Sb(?),but can only partially oxidize Sb(?);compared with Sb(?),the strain has a stronger tolerance to Sb(?),but not capable of reducing Sb(?).(2)The presence of oxidoreductase in Proteus cibarius DSHN0704 may be the reason for its ability to oxidize antimony;the existence of sulfide:quinone oxidoreductase(SQR)and catalase(CAT)may be the reason for certain antimony resistance;the pathways of microbial metabolism in diverse environments,energy metabolism,carbohydrate metabolism,amino sugar and nucleotide sugar metabolism may provide energy and growth-requiring substances of the strain for its antimony resistance.2.The optimized cultivation of Proteus cibarius DSHN0704 and the preparation of FMPAs were studied.The optimal cultivation of Proteus cibarius DSHN0704 under different nutrient factors and environmental influence factors was studied,and Proteus cibarius DSHN0704 was modified by Fe Cl₃ to prepare FMPAs.The research results showed that,(1)After the optimized cultivation,the removal rate of Sb by the strain has been obviously improved,and the removal rate of Sb(?)by Proteus cibarius DSHN0704 reached 24.90%at the optimal condition.(2)After the optimized cultivation,may due to the production of more EPS in its plasma membrane,the polysaccharides in EPS produce more functional groups that bind to Sb(?),thus,the removal rate of Sb has been greatly improved.(3)The surface of FMPAs has many massive bonding protrusions,and the structure of gaps and holes is obviously increased,which provides more adsorption sites,and the iron after Fe(?)modification is successfully loaded on the surface of the adsorbent.3.The optimization study on the adsorption of Sb(?)and Sb(?)by FMPAs was carried out.The optimization and comparison of Sb(?)and Sb(?)removal process by FMPAs using response surface method.The results showed that,(1)The optimal condition for FMPAs to adsorb Sb(?)are:adsorption time 2.17 h,adsorbent dosage 3343.67 mg/L,p H=6.0,temperature 44.41?,initial concentration of Sb(?)27.74 mg/L,and prediction accuracy is up to 98.50%.(2)The optimal condition for FMPAs to adsorb Sb(?)are:adsorption time 3.0 h,adsorbent dosage 1910.04 mg/L,p H=2.31,temperature 44.96?,initial concentration of Sb(?)24.80 mg/L,and prediction accuracy is up to 97.91%.(3)FMPAs have good adsorption effect on both Sb(?)and Sb(V),and the adsorption equilibrium can be reached within 2?3 h.Under the same reaction conditions,the adsorption rate of FMPAs on Sb(V)is higher than Sb(?).4.The mechanism of the adsorption and removal of Sb(?)and Sb(?)by FMPAs was discussed.The isothermal adsorption models and adsorption kinetic models were used to fit the experimental data,and the characterization techniques including FTIR,SEM-EDS,XRD and XPS were used to characterize and analysis FMPAs before and after modification and adsorption,and explore the removal mechanism of antimony.The research results showed that,(1)The Langmuir and Pseudo-first-order model can well fit the adsorption process of Sb(?)and Sb(?)by FMPAs,The adsorption process is mainly chemical adsorption,and is determined by the boundary layer effect and external mass transfer effect.(2)It can be seen from the results that there are multiple functional groups in FMPA.Sb can replace Fe(?)and form new complexes with surrounding atoms to achieve antimony removal.(3)The removal of Sb(?)by FMPAs is through the combined action of oxidation and adsorption,while the removal of Sb(V)is mainly through adsorption.(4)The mechanism is via the hydroxyl group in Fe-O-OH,Polyose-Fe and EPS-Polyose-O-Fe(OH)₂ which forms a new complex Fe-O-Sb thereby removing Sb(?)and Sb(?),and-OH in X?Fe-OH is replaced with Sb(III)to form X?Fe-Sb,thereby achieving the purpose of adsorption and removal of antimony.