Study On The Removal Oil In Sea Water By Modified And Fixed Bacteria Biochar

With the increasing demand for oil and the increase of oil exploitation and transportation in the world,marine oil spill accidents occur frequently,which causes a serious threat to marine environment and ecological security.Biochar(BC)was produced by oxygen-limited pyrolysis of biomass materials,and it had the advantages of wide source of materials,simple preparation process and low price,at the same time,it had strong adsorption ability because of its many pores,large specific surface area and abundant functional groups,which can be used to repair marine oil pollution.In this study,corncob,pine sawdust and maize straw were used as raw materials to prepare biochar,and then modified by hydrochloric acid and iron salt to compare the removal effect of biochar and modified biochar on oil in seawater,and biochar were characterized by specific surface area,scanning electron microscopy,surface functional groups and point of zero charge.The effects of different material sources,pyrolysis temperature and modifier types and concentrations on the oil absorption performance of biochar were specified.The adsorption mechanism of modified biochar on oil was investigated by adsorption kinetics and adsorption isotherm model.In order to remove the adsorbed oil from biochar,the modified biochar was used as carrier to immobilize petroleum hydrocarbon degrading bacteria,and the optimum technological conditions were studied.By comparing indigenous bacteria,enriched bacteria,biochar,fixed bacteria biochar and the combination of indigenous bacteria and fixed bacteria biochar,the optimal conditions for removing marine oil spill were confirmed.By comparing the changes of bacterial community and diversity BC/water phase under the conditions of fixed bacteria and non-fixed bacteria,the effects of biochar addition on microbial community and diversity were investigated.The main conclusions were as follows:(1)Nine biochars were prepared by pyrolysis of corn cob,pine sawdust and maize straw biomass for 2 h,at 300?,400?and 500?.57 kinds of modified biochar were obtained when hydrochloric acid and ferric salt were used as modifiers.Compared with biochar,the pore structure of modified biochar was more complex,uneven,new micropores appeared,and the specific surface area and pore volume changed differently,the number of oxygen-containing functional groups on the surface decreased,and p H_pzc decreased.(2)Pyrolysis temperature,material source and modifier had significant influence on the oil absorption performance of biochar.The modification of the three biochars revealed that the oil absorption performance of the modified biochars were obviously improved,hydrochloric acid modification had a great effect on the oil absorption performance of CCBC and PSBC,but the oil absorption ability did not increase with the increase of hydrochloric acid concentration;iron salt modification had the greatest effect on MSBC.the maximum adsorption capacity of three biochars were 2.12 g/g(10H400-CCBC),2.18 g/g(5H400-PSBC)and 2.17 g/g(Fe500-MSBC).(3)The adsorption process of modified biochar for oil in seawater was in accordance with the pseudo second order kinetic equation and Freundlich isotherm model.The adsorption process was mainly controlled by chemical reaction,surface diffusion and intraparticle diffusion and the adsorption was most favorable at 20?.(4)The fixation rates of petroleum hydrocarbon degrading bacteria on5H300-CCBC,5H400-PSBC and Fe500-MSBC were 42.75%,63.31%and 51.66%,respectively.The immobilization conditions were optimized,the results showed that the shaking speed and the fixation time had a great influence on the efficiency of biochar immobilized microorganisms,and the microbial inoculation amount had the least effect.The optimum combination was as follows:5H400-PSBC as the carrier,10%microbial inoculation,4h fixed at 180 r/min shaking speed.By comparing the removal rates of indigenous bacteria,enrichment bacteria,fixed bacteria BC,unfixed bacteria BC and the combination of indigenous bacteria and stationary bacteria BC,the results showed that the adsorption and degradation efficiency of indigenous bacteria and stationary bacteria BC was up to 93.05%,and the removal efficiency was much higher than that of indigenous bacteria and enrichment bacteria.(5)Alpha diversity analysis results showed that the sequencing results could truly reflect the richness and diversity of bacteria in the sample.The addition of stationary bacteria BC would change the diversity of the environmental microbial community.Compared with the water phase,the richness of the bacterial community in BC decreased,but the uniformity increased.Bac@BC,Bac@W,N@BC and N@W common OTUs were classified at the generic level,the dominant bacteria with high abundance were Acinetobacter(76.65%),Altererythrobacter(10.25%),Pseudomonas(2.83%),Alcanivorax(2.11%)and sphingomonas(1.11%).(6)Analysis of bacterial community structure in BC/water showed that there was little difference at phylum and class level,but great difference at genus level.The dominant bacteria of Bac@BC were Acinetobacter(82.04%),Altererythrobacter(5.77%),Pseudomonas(4.59%)and Sphingopyxis(2.22%),respectively.The dominant strains of Bac@W were Acinetobacter(71.39%)and Altererythrobacter(11.17%).While the dominant bacteria of N@BC were Acinetobacter(84.92%)and Altererythrobacter(9.35%),and the dominant bacteria of N@W were Acinetobacter(68.37%),Altererythrobacter(14.07%)and Alcanivorax(4.46%).However,these bacteria were all petroleum hydrocarbon degrading bacteria in the sea and had good removal effect on petroleum hydrocarbon in the seawater.The abundance of Pseudomonas in the Bac@BC was higher than that N@BC,which indicates that biochar can provide suitable living space for PAHs degrading bacteria and promote their mass reproduction,thus increasing the degradation rate of oil.