| Oil spill will not only cause huge economic losses,but also bring unrecoverable ecological disaster to the marine environment.After the oil spill accident,the physical and chemical methods can be used to clean up most of the spilled oil quickly,but the biodegradation method is the most economical and effective for the thin oi1 film,suspended oil and emulsified oil remaining on the surface of the sea water.The biological treatment of oil spill has three key problems:first,the oil composition is very complex,it is difficult to use a single strain to achieve an ideal degradation effect.Secondly,there are still some defects in the treatment of offshore oil slick by free biodegradable bacteria.Many problems such as poor lipophilicity,large proportion and poor adaptation to the environment lead to a large amount of loss of degrading bacteria when put into the ocean.Thirdly,the process of biodegradation of spilled oil in the ocean is very complex,and the feasibility of using classical kinetic model to deal with the lack of a large number of experimental data of spilled oil is verified.In view of the above problems,this thesis focuses on the influence of microflora,carrier and oil spill degradation performance.The main results are as follows:(1)The mixed microflora was constructed to solve the problem of simultaneous degradation of oil spills.Five kinds of highly efficient petroleum hydrocarbon degrading bacteria were isolated from beach sediments polluted by oil spills,and composed of microflora MF3711.Through morphological observation and construction of 16s rDNA,the microflora was identified as bacillus,pseudomonas,alkanogens,marinobacter and micrococcu.After optimizing a series of environmental conditions,such as temperature,salinity,pH value and biosurfactant,the 7 d degradation rate of the microflora increased from 72.24%to 92.67%.The analysis of the residual oil components showed that the microflora had synergistic effect during the degradation process,so it could degrade the multi-component in the oil spill at the same time.In order to explore the mechanism of microflora degradation,rhamnolipid(Rha)was used as a lead compound,and a new algorithm of solvent system was proposed and established for separation and purification of secondary metabolites of bacteria by high-speed countercurrent chromatography.Six kinds of Rha with purity higher than 84.41%were obtained by one-step separation and purification.The hydrophobicity,solubilization and emulsifying properties of the cells added with Rha were studied.The results showed that the concentration of Rha was positively correlated with the enhancement of hydrophobicity on the surface of the cells.The addition of high concentration of Rha is helpful to the emulsifying and degradation of alkanes.(2)In order to solve the problem of low biodegradation efficiency,a series of floating,hydrophobic and biocompatible immobilized carrier were prepared to increase the effective contact between bacteria and oil slick.Firstly,the prepared macroporous SA/PVA carrier with contact angle 9 of 149.3000,and mechanical strength of 2.52 mN.The floating property of the carrier was realized by adjusting the proportion and density of the components.Then,using polylactic acid as the substrate,the floating hydrophobic macroporous carrier(RMPLA),was prepared by physical and chemical methods,which carried polar groups inside and grafted hydrophobic aliphatic polyester into the outside.The saturated adsorption rate of RMPLA to oil particles was up to 18.17 g/g,and the degradation rate of immobilized bacteria was 88.95%in 7 days.Finally,Fe3O4 nanoparticles were modified by PEG and SDS to obtain amphiphilic colloidal magnetic nuclei.Magnetic Fe3O4StMD carriers with contact angle ? of 133.4°and specific saturation magnetization of 3.95 emu/g were prepared by dispersion polylerization.This technology can be widely used in the treatment of emulsified oil wastewater from ship engine room.After 12 h degradation,the degradation rate of emulsified oil treated by immobilized bacteria was increased by 13.86%,which showed that the reaction start-up was fast and the treatment efficiency was high.Therefore,the degradation of oil spill pollution by immobilized bacteria is expected to be an effective alternative to solve the problem of marine oil pollution.In order to analyze the degradation intermediate products of microflora,Fe3O4MNG@CTAB was prepared as dispersed solid phase extraction material.The degradation intermediates of polycyclic aromatic hydrocarbons and phenanthrene were detected.The results showed that the detection limit was up to 1.5?5.0 ng/L.The recovery rate was 74.01%and 94.67%respectively.The results showed that through two metabolic pathways,salicylic acid and phthalic acid,the microflora finally completely degraded the oil spill.(3)The applicability of the classical kinetic equation was verified by the experimental data,and the speed-limiting step of biodegradation of spilled oil by microflora was defined.The quasi-second order kinetic model is suitable for describing the adsorption effect between the carrier and the oil spill.The apparent activation energy(Ea)is 21.65 kJ/mol,and the adsorption process of the carrier is physical adsorption.Through the analysis of adsorption kinetics,it is proved that the intra-particle diffusion is not the only rate control step in the adsorption process.The biodegradation kinetics of phenanthrene showed that the adsorption rate of phenanthrene was much higher than that of phenanthrene,which resulted in the enrichment of phenanthrene on the surface and interior of the bacteria.The degradation rate of phenanthrene was much higher than that of its dissolution.It is concluded that the dissolution process is the rate-limiting step for microbial degradation of spilled oil.The results of this study can provide universal theoretical support for the application of large-scale micro flora to the control of marine oil spill pollution. |
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