| Wastewater containing U（Ⅵ）has the toxicity of heavy metals and radioactive,which damage to the environment and human health.Bioremediation,composited with advantages of good environmental benefits and low investment,is hot topic in the fields of radioactive wastewater treatment.The biological sulfur iron composites produced by sulfate-reducing bacteria（SRB）.The key factors affecting the preparation of biological sulfur iron,and effects of initial U（Ⅵ）concentration,pH values and temperatures on U（Ⅵ）removal by biological iron sulfide composites and its particle size were investigated.The properties and removal mechanisms of biological sulfur iron were analyzed via environmental scanning electron microscope（SEM）,flourier transform infrared spectroscopy（FTIR）and high-resolution transmission electron microscopy（TEM）-X-ray spectroscopy（EDS）.The community structure was also analyzed.The results of this work are as follow:The results indicated that the maximum output of biological sulfide iron（natural weight:3.56g,dry weight:0.51g）occurred at FeCl2 of 0.3g,SRB inoculums amount of 10%,pH of 7.5 and time of 3d.The ratio of natural weight to wet weight was 14%,which illustrated that biological sulfide iron have high microbial activity and good microbial structure.SEM and TEM images showed that the sulfide iron within biological sulfide iron was amorphous and irregular prisms,which was about20150nm thickness and 200nm1μm length.The results showed that the maximum removal capacity was obtained under the conditions of initial pH of 7.5,temperature of 35℃,initial U（Ⅵ）concentration of 7.2mg/L and biological sulfur iron composites dosage of 0.1g.The treatment equilibrium was obtained at12 h and the ultimate U（Ⅵ）removal rate reaches 99.5%.The U（Ⅵ）removal rate by biological sulfur iron composites was better than that of sulfur iron and SRB.U（Ⅵ）could be adsorbed and reduced by sulfur iron and SRB in the activated biological sulfur iron composites with advantages of high efficiency.The measurement of laser particle size found that the particle size of biological sulfide iron varied with the U（Ⅵ）removal efficiency,and the maximum particle size was 46.47μm under the maximum uranium removal rate.FTIR spectra demonstrated that hydroxyl group,carboxyl group,phosphoric acid group,C=O,C-N,and P-O involved in uranium deposition.SEM images showed that the sulfide iron within biological sulfide iron was amorphous and irregular prisms,which was about20150nm thickness and 200nm1μm length.And it revealed that the U（Ⅵ）removal mechanisms were extracellular adsorption and intracellular accumulation by TEM-EDS.In addition,the uranium characteristic peaks were obvious accounting for 9.70%in total elemental mass fractions,which demonstrated that the biological sulfur iron had excellent U（Ⅵ）removal capacity.Bio-sulfur iron composite material contains many strains,including the typical uranium reduction fixed bacteria:Enterobacter,Acinetobacter,Citrobacter,Desulfovibrio and so on.Commonly able to deal with sewage microorganisms include:Proteiniclasticum,Macellibacteroides,Eubacterium,Acidaminococ-caceae,Sedimentibacter.The presence of these microorganisms has a catalytic effect on bio-sulfur iron to adapt to complex environmental wastewater. |
