Adsorption And Degradation Of PAHs In Environment By Loofah And Its Immobilized Microorganisms

Polycyclic aromatic hydrocarbons(PAHs)causing serious environmental pollution are persistent organic pollutants.Biomass materials withstrong adsorption capacity for PAHs can be used as a good carrier for immobilization of microorganisms.Therefore,immobilization of microorganisms using biomass materials as carriers is an effective way to remove soil PAHs.However,the complex adsorption-biosorption and biodegradation processes at the soil-microbial interface are the difficulties in current research,and the relationship between whichis still unclear.Therefore,it is important to study the adsorption and degradation process.This paper summarizes the adsorption and degradation principles and influencing factors of PAHs at home and abroad and discusses the application of loofah in the environment.It proposes the immobilization of microorganisms with biomass loofah and the adsorption of PAHs in the environment-Research on degradation.In this paper,through different modifications to the loofah biomass materials:unmodified(UM),alkalized modified(AL),acid-decomposed modified(AH),high-temperature and high-pressure modified(HC),the loofah biomass materials modified were to study the adsorption characteristics of trace PAHs in water.The results showed that the surface structure of the modified loofah changed by SEM,and the high temperatur e and high pressure modified loofah had the largest surface wrinkles and the largest specific surface area.According to the infrared characterization,the increase or decrease of the adsorption capacity of loofah on polycyclic aromatic hydrocarbons might be related to changes in methyl,triple bond,amide,aromatic C=C and cellulose.The adsorption relationship of four loofahs to Phe and Pyr was HC>AL>UM>AH.The adsorption processes of Pye and Pyr by four loofahs were all subject to quasi-secondary kinetics,and the adsorption mechanism is more consistent with the Langmuir adsorption model of monolayer adsorption.On this basis,the competitive adsorption mechanism of high temperature and high pressure modified loofah and soil to Phe was studied,and the migration behavior of Phe under different conditions in the soil with high temperature and high pressure modified loofah was investigated.The results showed that the equilibrium adsorption of modified loofah(CK-loofah),soil(CK-soil),modified loofah inthemixture(LS-loofah),soil in themixture(LS-soil),themixture(LS)to Phe were 64.26,94.58,11.23,86.32 and 97.56μg,respectively.After the modified loofah is mixed into the soil,the competitive adsorption process of LS-loofah to Phe was subject to the quasi-secondary kinetic model,and the competitive adsorption process of LS-soil and LS to Phe was subject to the quasi-first-order kinetic model.The equilibrium migrationamounts of Phe in pH=7 soil,pH=6 soil and pH=8 soil were 5.36,10.73,9.17μg,respectively.During the migration of Phe from soil to modified loofah,the adsorption process of modified loofah toPhe was subject to the quasi-second-order dynamic model.Studies have shown that the adsorption capacity of the wholeadsorbent increases when the modified loofah is added to the soil.The adsorption mechanism and characteristics of soil system cannot be affected when adding biomass cannot make soil organic carbon close to or reach the saturated level.Compared with pH=7,when pH=6 or 8,the migration of Phe in soil increases.The adsorption process of modified loofah to Phe belongs to chemical adsorption.In order to study the combined effect of immobilized microorganisms on soil PAHs biosorption and biodegradation,Pseudomonas sp.SDR4(S4)and Mucormucedo sp.SDR1(S1)were used as research objects to study the adsorption and degradation of PAHs in soil by immobilized microorganisms.The adsorption mechanism,degradation kinetics,and relations between adsorption and degradation of the immobilized microorganisms to PAHs in soil were examined.The results showed that after 60 d,the dynamic equilibrium adsorption of modified loofah(CK),dead immobilized S1(S1-D),dead immobilized S4(S4-D),and dead immobilized mixed bacteria S1 and S4(S1+S4-D)to phenanthrene(Phe)was 5.28,6.82,5.73,and 7.46μg,respectively,and the dynamic equilibrium adsorption of pyrene(Pyr)was 4.17,4.72,4.53,and 5.00 μg,respectively.The adsorption of dead immobilized microorganisms to Phe and Pyr was subject to quasi-second-order dynamics.The dynamic adsorption capacities of living fungi S1,bacteria S4,and mixed bacteria S1+S4 to Phe were 2.32,2.01,and 2.76 μg,respectively,and the dynamic adsorption amount of Pyr was 2.79,2.41,and 3.14 μg,respectively.Quasi-first and quasi-second-order kinetics of Phe and Pyr adsorbed by living immobilized microorganisms in soil showed little difference in R2 fitting re-sults.The degradation rates of S1,S4,and S1+S4 to Phe were 54.34%,61.45%,and 64.23% respectively,and the degradation rates of Pyr were 38.42%,35.02%,and 42.43%,respectively.Following treatment with S1,S4,and S1+S4,the half-lives of the degradation of Phewere 38.88,29.41,and 25.63 d,respectively.The half-lives of the degradation of Pyr were 64.76,69.02,and 59.28 d,respectively.The research showed that chemical action was the main factor that controls the adsorption rates of immobilized microorganisms of loofah to PAHs.The enhanced degradation ability of microorganisms could increase the influence on the migration of PAHs in soil.The synergistic effect between fungi and bacteria could improve the degradation efficiency of Phe and Pyr.