Adsorption Of Surfactant In Soil And Its Effect On Microbial Remediation

Cationic surfactant cetyltrimethylammonium bromide(CTMAB),nonionic surfactant Tween-80(Tween-80)and anionic surfactant sodium dodecylbenzene sulfonate(SDBS)were selected to carry out the kinetic and isothermal adsorption experiments of soil surfactants,and to determine the best kinetic and isothermal adsorption models.Through single factor experiments,the effects of soil organic matter content,temperature and pH on the adsorption behavior of surfactants at soil interface were explored,and the adsorption mechanism of three surfactants in soil was determined.Based on the adsorption results,SDBS with small adsorption residues was selected to investigate its effect on the degradation of petroleum hydrocarbons by WH efficient petroleum hydrocarbon degrading bacteria.Straw immobilized microorganisms were prepared by WH bacteria to remediate petroleum-contaminated soils with different SDBS contents.The degradation rate of petroleum hydrocarbons and the change of microorganism number in soil system during remediation were investigated to determine the effect of SDBS on soil microbial remediation process and the optimal remediation conditions.The results are as follows:(1)The adsorption kinetics of cationic surfactant CTMAB,anionic surfactant SDBS and non-ionic surfactant Tween-80 in soil is suitable to be described by quasi-second-order kinetics model.(2)The isothermal adsorption process of SDBS in soil is suitable to be described by Langmuir isothermal adsorption model;the isothermal adsorption process of Tween-80 in soil is suitable to be described by Freundlich isothermal adsorption model;the isothermal adsorption process of CTMAB in soil is related to the equilibrium concentration of CTMAB,and is suitable to be described by Langmuir isothermal adsorption model when its equilibrium concentration is lower than the critical micelle concentration.When the equilibrium concentration is higher than the critical micelle concentration,the Freundlich isothermal adsorption model can be used to describe it.(3)System temperature was negatively correlated with the equilibrium adsorption capacity of CTMAB and SDBS,and positively correlated with the equilibrium adsorption capacity of Tween-80;Soil organic matter content was negatively correlated with the equilibrium adsorption capacity of CTMAB,positively correlated with the equilibrium adsorption capacity of SDBS,but not with the equilibrium adsorption capacity of Tween-80;System pH was positively correlated with the equilibrium adsorption capacity of CTMAB,but positively correlated with the equilibrium adsorption capacity of SDBS and Tween-80.Quantities were negatively correlated.(4)In liquid medium,when the concentration of SDBS reached 100 mg/L-1,the degradation rate of petroleum hydrocarbons was the best,reaching 33.69%.When the concentration of SDBS in liquid medium was low or high,it could inhibit the degradation of petroleum hydrocarbons by WH bacteria.(5)The remediation effect of straw immobilized WH-efficient petroleum hydrocarbon degrading bacteria is better than that of free WH-efficient petroleum hydrocarbon degrading bacteria and indigenous bacteria.When the SDBS content of the repair system was 500 mg,the straw immobilized WH bacteria had the best repair effect,and the degradation rate of petroleum hydrocarbons reached 53.45%.(6)In the process of combined microbial remediation with surfactant treatment,the leaching residue of surfactant can be controlled within the scope of subsequent microbial remediation by adjusting the parameters of temperature,pH and soil organic matter content,so as to improve the efficiency of combined remediation and reduce secondary pollution.