Study On Chemical And Microorganisms Combined Remediation Of Polycyclic Aromatic Hydrocarbon Contaminated Soil

Polycyclic aromatic hydrocarbons(PAHs)are a kind of strong carcinogenic organic pollutants.Due to the influence of human industrial activities such as chemical production,the utilization of PAHs contaminated soil is severely restricted with environmental risks.In this study,the degradation effect of anthracene,phenanthrene and pyrene in soil polluted by H₂O₂,Fenton reagent,KMn O₄ and sodium persulfate was studied.Sodium persulfate was selected as oxidant to optimize the degradation conditions and degradation mechanism of anthracene.Three polycyclic aromatic hydrocarbons(PAHs)degrading bacteria were domesticated and isolated from the activated sludge of coking wastewater.Through the combined remediation method of sodium persulfate oxidation followed by inoculation of degrading bacteria,PAHs contaminated soil had a good remediation effect.The conclusions are as follows:H₂O₂,Fenton reagent,KMn O₄,Persulfate four kinds of oxidants to anthracene,phenanthrene,pyrene,three kinds of contaminated soil were oxidative degradation effect,anthracene and phenanthrene degradation rate is between 50-78%,the rate of degradation and oxidant concentration were positively correlated,pyrene degradation rate is between 36%and 47%,With the same concentration of oxidant,sodium persulfate has the best oxidation effect.The degradation rate of anthrene and pyrene by 50 mmol/L sodium persulfate is 72.81%,71.77%and 43.58%,respectively.H₂O₂ and Fenton reagent can destroy the soil particles,and KMn O₄ can affect the total manganese content in the soil.Persulfate is chosen as the oxidant for the combined remediation.The kinetic model of degradation of anthracene by persulfate with different concentrations was established,which was in line with the first-order reaction,and the reaction rate constant k was between 0.0178 and 0.0833 h^-1.The experiment of free radical quenching agent shows that two kinds of free radicals,SO₄^-·and·OH,are produced during the oxidation and degradation of anthracene by sodium persulfate.·OH is the dominant free radical.At the end of the reaction,the mineralization rate of anthracene was 46.61%,which was lower than the degradation rate of anthracene,indicating the accumulation of intermediate products.Four intermediate products of 9,10-anthraquinone,2-hydroxybenzoic acid,diethyl 1,2-benzodiarboxylic acid and naphthalene-2,3-dicarboxylic acid were identified.It is speculated that the degradation pathway of anthracene can be divided into two degradation pathways:oxidized 9,10-?carbon and oxidized 1,4,5,8-?carbonFe²⁺can activate sodium persulfate,and the optimal dosage is 40%sodium persulfate concentration.Adding Tween-80 can increase the degradation rate of anthracene from 67.89%to 77.04%by sodium persulfate.50 mmol/L sodium persulfate decreased soil p H from 7 to 4.83,and the number of microorganisms decreased from 2.3×10⁷ CFU/g to 3.7×10⁶ CFU/g.After 14 days,the soil gradually recovered to the normal level.The specific surface area of soil particles increased from 61.08 m²/g to 81.19 m²/g after oxidation,and the surface irregularity of soil particles increased,and hollow layered structures appeared.Three polycyclic aromatic hydrocarbons(PAHs)degrading polycyclic aromatic hydrocarbons(PAHs)were domesticated and isolated from coking wastewater by adding"xylene-catechol-PAHs",and the result of molecular biology identification was Bacillus.The degradation rates of anthracene,phenanthrene and pyrene by degrading bacteria were 64.62%,61.69%and 31.47%at 14 d,and the addition of Tween-80 could increase the degradation rates of PAHs by 21%.There are microorganisms that can degrade PAHs naturally in the soil.Adding inorganic nutrients to the soil can degrade an THRacene by 27.13%.After adding 50 mmol/L activated sodium persulfate for oxidizing for 7 days,and then inoculating degrading bacteria and adding inorganic nutrients,the combined remediation efficiency of anthracene,phenanthrene and pyrene contaminated soil for 35 days was 94.94%,93.52%and 66.24%,respectively.The combination of chemical oxidation and microorganism has a good effect on remediation of PAHs contaminated soil.