Biosynthesis And Application Of Selenium (Tellurium) Nanomaterials

In recent years,the use of dyes has become more and more frequent in our daily life.However,the widespread use of dyes pollutes the water bodies in the environment.Among them,Malachite green was once widely used in fishery production due to its efficient bactericidal properties,which caused a huge burden on environmental water bodies.At the same time,adsorption materials with good adsorption capacity and fast adsorption rate have received more and more attention.Nanoparticles are often used as highly efficient adsorbents because their have highly specific surface area.such as Se-NPs,ZnO NPs and AgNPs.However,the existing preparation methods of nanoparticles often have disadvantages such as high environmental pollution,high cost and harsh reaction conditions,so it is particularly important to find a green synthesis method.Some microbes,such as certain bacteria,fungi,and yeasts,can survive in concentrations of metal ions,grow,oxidize and reduce these metal ions,and convert them into corresponding nanoparticles.Therefore,using microorganisms to reduce and oxidize pollutants and synthesize required nanoparticles is undoubtedly a green way to obtain nanoparticles.In fact,due to their green and harmless characteristics,biosynthetic nanomaterials have been widely used in many fields.In this thesis,Selenium nanoparticles and tellurium nanoparticles were prepared by using strains Rhodotorula Mucilaginosa PA-1 and Achromobacter Xylosoxidans DQ-3,respectively,the adsorption properties of the synthesized selenium（tellurium）nanoparticles on malachite green were investigated.（1）Selenium nanoparticles were synthesized using the strain Rhodotorula mucilaginosa PA-1 screened out in the laboratory,and a series of characterizations were carried out.In addition,the most appropriately experimental condition for the synthesis of selenium nanoparticles was explored,which was OD₆₀₀=0.5,0.5 mmol Na₂SeO₃,pH=8,35℃according to the tested results.Under this condition,it only took 24 hours for the synthesis of Bio-Se NPs.（2）The adsorption of malachite green on selenium nanoparticles was studied.The experiment confirmed that selenium nanoparticles had a strong ability to remove malachite green under the condition of pH=10,that is,the pH value could affect the adsorption of the selenium nanoparticles to the cationic Dye Malachite Green.The experiment confirmed that the data of malachite green adsorption by Selenium nanoparticles were highly consistent with the pseudo-first-order model,which was physical adsorption.The data of isothermal adsorption on MG showed that the adsorption process had the highest correlation with Langmuir model,and the adsorption process was dominated by monolayer adsorption.Under the conditions of 303,313 and 323 K,the removal rate of the dye decreased with the increase of temperature,and the adsorption capacity were 1 355.39,1 095.49 and 898.62 mg/g,respectively.The adsorption performance of malachite green was better than that of common biomass materials.Adsorption thermodynamics study,malachite green on selenium nanoparticles adsorption was a spontaneous exothermic reaction.In addition,after 5 cycles,the adsorption capacity of Se nanoparticles was still excellent,the removal rate was as high as82.12%.（3）In the experiment,nanometer tellurium was biologically synthesized by strain Acromobacter xylosoxidans DQ-3,and the material was physically characterized.At the same time,the best synthesis conditions of the material were explored:OD₆₀₀=0.5,0.1 mmol Na₂TeO₃,pH=8,35℃.Under these conditions,it took only 30 h to synthesize Te nanoparticles.In addition,we applied this material to the adsorption of malachite green,a triphenylmethane dye.It had been proved that nano tellurium has a strong ability to remove malachite green under the condition of pH=10,that is,the pH value had the ability of affecting the adsorption of cationic dye malachite green by nano tellurium.It was proved that the adsorption data of nano tellurium malachite green was highly consistent with the pseudo-second-order model and was chemical adsorption.The data fitting of isothermal adsorption on malachite Green showed that the adsorption process was most correlated with Langmuir model,and the adsorption process was dominated by monolayer adsorption.Under the conditions of 303,313 and 323 k,the removal rate of dye decreased with the increase of temperature,and the adsorption amounts were 738.55,651.04 and 566.97 mg/g,respectively.The study of adsorption thermodynamics showed that the adsorption of MG on Bio-Te NRs was a spontaneous exothermic reaction.In addition,after 5 cycles,the adsorption capacity of Te-NRs was still excellent,and the removal rate was still above 70%.