Antimony Removal From Water Using Freshly Formed Chitosan-biogenic Fe-Mn Oxide:Preparation And Adsorption Mechanisms

Antimony is an important raw material for industrial uses.Significant industrial activities and the burning of fossil fuels release a large amount of antimony into water,soil and atmospheric environment.Therefore,the use of efficient,low-cost,easily recoverable adsorbents to remove antimony in wastewater has become a research hotspot at home and abroad.In this study,a Fe-Mn oxidizing bacterial consortium was screened and acclimated from the acid mine drainage(AMD)containing high concentrations of iron and manganese.The biogenic Fe-Mn oxides(BFMO)which was produced by Fe-Mn oxidizing bacterial consortium could be used as a good bio-sorption material.Hence,a novel material(CH-BFMO)was prepared by the biogenic Fe-Mn oxides and chitosan(CH)and was used to remove antimony from water.After that,SEM,XRD and BET were used to investigate the physical and chemical properties of CH-BFMO,and then the adsorption performance of CH-BFMO for Sb(?)and Sb(?)was explored through static adsorption experiments.The adsorption behavior mechanism of Sb(?)and Sb(?)on CH-BFMO was investigated through kinetics,isotherms and thermodynamics.In addition,the effects of initial pH,ionic strength,coexisting ions,and the dosage of adsorbent on the adsorption of Sb(?)and Sb(?)by CH-BFMO were investigated.Finally,the potential adsorption mechanism was analyzed by FTIR,EDS and XPS techniques,and the main results were showed as follows:(1).A bacterial consortium was enrichment from Qibaoshan mine,Liuyang City,Hunan province.And after acclimated,the maximum tolerable concentration of Fe for the acclimated bacteria was 1000 mg/L,and Mn was 500 mg/L.High-throughput sequencing of the 16S r RNA genes demonstrated that the microbial community had changed substantially during the treatment.At phylum level,the relative abundance of Proteobacteria was greater than 92.75%during the culture process,and the relative abundance of these bacteria was increase from 93.10%to 97.84 at the end of culturing,which was suggested that Proteobacteria was the dominant bacteria.At genus level,the Mn oxidizing bacteria Pandoraea and Stenotrophomonas was the main bacteria and may play an important role in the consortium.(2).A novel bio-adsorption material was prepared by the biogenic Fe-Mn oxides BFMO and chitosan.After synthesized,the surface morphology was analyzed by SEM and the results showed that both BFMO and CH-BFMO were characterized by a porous honeycomb shape and contained bacterial components on the surface.CH-BFMO is more compact than BFMO,which was benefit for recycle.Both BFMO and CH-BFMO are amorphous structures,and CH-BFMO has a large specific surface area than BFMO,which was further improved the adsorption.The adsorption process of Sb(?)and Sb(?)is more suitable for the Pseudo-second-order kinetic model,which was indicated that the adsorption behavior was mainly chemical adsorption.The Langmuir equation can well describe the adsorption process of Sb(?)and Sb(?)by CH-BFMO,which indicated the adsorption process of Sb(?)and Sb(?)belongs to the monolayer adsorption,and multilayer adsorption also occurs.The optimal pH of the adsorption of CH-BFMO to Sb(?)and Sb(?)were around 4.0 and 6.0 respectively.Regeneration experiments were that the removal rate of Sb(?)and Sb(?)by the adsorbent after five times of desorption regeneration remains high and stable.It shows that the CH-BFMO is recycle repeatedly for many times after regeneration,and it has strong recyclability and stability.(3)Adsorption mechanism of Sb(?) and Sb(?)by CH-BFMO were investigated using FTIR,XPS and SEM-EDS analysis.The results showed that the functional groups C=O,C=C,O-H were on the surface of CH-BFMO,which also improved the removal efficiency of Sb.The results of SEM-EDS showed that the content of Sb(?)and Sb(?)on the CH-BFMO surface was in increased significantly,the content of Sb(?)increased to 8.61%and the content of Sb(?)increased to1.88%.Moreover,it can be obtained from the XPS results that not only Sb₂O₃ but also Sb₂O₅ were present on the surface of CH-BFMO after the adsorption of Sb(?),which indicated that the removal of Sb(?)was not only by chemical adsorption but also by oxidation.On the other hand,Sb₂O₅ was the mainly form on the CH-BFMO after adsorbing Sb(?),and it means that the adsorption of Sb(?)was mainly by chemical adsorption.