Research On Characteristics And Sorption Properites Of Extracellular Polymeric Substances(EPS)from Bacillus Vallismortis Sp.under The Stress Of Sulfide

With the development of China's economy,the problem of heavy metals in water has become increasingly serious.Bio-adsorption method is a hot topic in the treatment of heavy metal wastewater.Compared with traditional methods,it has the advantages of high efficiency,economy,and no secondary pollution.Extracellular Polymeric Substances?EPS?is a type of biosorbent that has good adsorption of heavy metals.However,little is known about the effect of sulfur ions on the bacterial and EPS properties.Under certain environmental conditions,microorganisms produce a poly-compound during metabolism and surround the microbial cell wall,including the mucus layer and other surface substances.According to research,these poly-compounds are mainly composed of polysaccharides,lipids,lipopeptides,and nucleic acids.The EPS a large number of functional groups and has good adsorption properties for heavy metals in wastewater.In this experiment,aniline aerofloat high efficiency degradation bacterium Bacillus vallismortis sp.,adding different concentration gradient of the cultivation of the sulfur ions stress,analyzed the components of EPS and output,and studies the sulfur ions stress effect on the properties of EPS adsorption.Scanning electron microscopy?SEM?,Fourier transform infrared spectroscopy?FTIR?,and three-dimensional fluorescence spectroscopy?3D-EEM?were used to analyze the mechanism.With stress after EPS as heavy metal absorbents,studied its adsorption capacity and adsorption behavior.The main results are as follows:1.When the sulfide ion concentration was 40 mg/L,EPS production increased to89.6mg/L.The maximum adsorption capacity of Cu²⁺and Zn²⁺were 1.44mg/mg and1.41mg/mg.When sulfur ion concentration was increase to 80 mg/L,the adsorption capacity was declined.2.Observed from the SEM image,the thickness of the viscous material on the surface of the bacteria increased after sulfur ion stress;The results of three-dimensional fluorescence spectroscopy showed that the stress of sulfur ions led to the increase of tyrosine and tryptophane-like,some fulvic acids and some humus in EPS.3.FTIR analysis does not change the type of EPS functional groups after sulfur ion stress,but it affects EPS components and thus increases the relative concentration of some active functional groups in EPS.The increase in these groups?sulfhydryl groups?helps to increase the coordination of EPS with metals.4.The results of adsorption experiments showed that:with the increase of pH value and the temperature,the adsorption amount of EPS of before and after sulfur ion stress were increased.Adsorption of EPS before/after the stress increased with the initial concentration of metal.Within the initial concentration of 50 mg/L,the influence of S-EPS is greater than Control-EPS.The Adsorption capacity of two EPS were reached more than 1.8mg/mg.5.The adsorption of S-EPS and Control-EPS were conformed to level 2 dynamic model.Langmuir model and Freundlich model could describe the thermodynamics sorption processes of EPS.The Langmuir model's fitting effect with the measured value of the EPS of before/after sulphur ion stress adsorped Cu²⁺and Zn²⁺was better than the Freundlich model.Calculated by the model:the maximum adsorption capacity of Cu²⁺and Zn²⁺by S-EPS were 2.272 mg/mg and 2.054 mg/mg.6.Sulfide ion can produce specific EPS through the stress bacteria,provide a large number of binding sites for heavy metal ions in wastewater,and significantly increase the ability of EPS to remove heavy metals.The research results have certain guiding significance for improving the biological treatment of wastewater containing heavy metals.