Nitrates And Microplastics Removal Studies In A Microbial-dominated Environment

As one of the most important available resources on the earth,water is an important part of maintaining the ecological balance on the earth and guarantees the production and life of human beings.However,due to the current economic and social development,water bodies have been severely polluted.Among them,nitrate nitrogen is one of the most important components of water pollution indicators.After being taken into the human body,nitrate is partially reduced to nitrite under the action of reducing bacteria.Nitrite can combine with hemoglobin to lose its oxygen delivery function..High concentrations of NO₃-can form the"three-factor"substances nitrosoamine and nitrosamide in the body with nitrogen-containing organic compounds.FeNPs is considered to be an effective method to remove nitrate nitrogen.FeNPs is currently widely used in sewage treatment due to its special size effect,surface effect,and high activity.However,the characteristics of FeNPs are also a double-edged sword,with the advantages of large specific surface area and high activity.It also brings the shortcomings of easy agglomeration and instability,which limit its application in sewage treatment and other aspects.As a new type of hot pollutant,microplastics are generally less than 5 mm in diameter.With the large-scale use of plastic products,the term microplastics has entered people's daily lives,and microplastics have become A worldwide environmental problem alongside global warming,greenhouse effect and ozone.Based on the above problems,this article uses the biological reduction characteristics of microorganisms to directly reduce the nanoparticle precursors into nanoparticles.By screening denitrifying bacteria with excellent denitrification function in the soil,the method of continuously cultivating denitrifying bacteria for several generations will be Nanoparticles were successfully loaded on denitrifying bacteria,Become denitrifying bacteria-Iron nanoparticles(FeNPs)composite material,which were used to remove nitrate nitrogen in water bodies.In addition,we also used the biological metabolism of microorganisms to study the degradation mechanism of microplastics in facial cleansers.The main research contents are as follows:(1)Denitrifying bacteria-Iron nanoparticles(FeNPs)composite material was characterized by UV-Vis,XPS,FTIR and TEM,confirming that FeNPs are embedded in the bacteria and fully protected by the bacteria.This composite material can remove nearly 100%of nitrate-N in 420 minutes without generating more ammonia nitrogen.The FeNPs loaded in the denitrifying bacteria-FeNPs composite material can act as an electron donor for denitrifying bacteria to complete the biological denitrification process,which will accelerate the denitrification rate to remove nitrate-N faster.FeNPs are synthesized through the biological reduction ability of denitrifying bacteria,without adding other chemical reducing agents,and denitrifying bacteria can protect FeNPs from oxidation in the environment.(2)New pollutant microplastics were extracted from facial cleansers,and characterized by FTIR,RAMAN,CLMS,EM,etc.,Raman spectroscopy and FTIR spectrometry identify the main substance of the separated microplastics is PE.CLSM images stained with Nile red reveal the shape and size of the microplastics.EDS elemental maps suggest the C/O ratio in the microplastics.The bacteria used without domestication by microplastics exhibit an efficient performance in degrading of microplastics by metabolizing.(3)Using the biological metabolism of microorganisms to biodegrade microplastics,studies have found that The bacteria grew and inhabited on or in the microplastics,and then metabolized them.0.22 g of microplastics on the filter paper(d=50mm)can be degraded completely after 33 days.