Studies Of Chemical Washing On Removal Of PAHs And Heavy Metals From Abandoned Coking Plant Contaminated Soil

With the adjustment of industrial structure,the coking wasteland has increased year by year.Polycyclic aromatic hydrocarbons(PAHs)and heavy metals(Cd,Zn,Hg,etc.)are the characteristic pollutants in the polluted soil,that residual concentration is high.Nowadays,serious soil pollution problems have aroused people attention.Aiming to screen out the best surfantants and obtain its optimal conditions,this study investigated the removal of PAHs and heavy metals in multi-contaminated soil of the coking wasteland by batch experiments using surfactants and mixed chelators(MC).At the same time,the effects of the addition order of Tween 80(TW80)and MC on the removal of PAHs and heavy metals were also found.The study has shown that under the same concentration conditions,the removal rates of 16 kinds of PAHs in the soil by TW 80,Triton 100(TX-100)and alkyl glycoside(APG)are 25.67,18.89 and 16.77% respectively.Hence TW80 is chosen as the optimal eluant.The removal rate of PAHs in coking contaminated soil reaches equilibrium in four hours.With TW 80 concentrations increasing,the PAHs removal rate in coking contaminated soil also accelerate.When the p H of the TW 80 eluent was 5,the removal rate of PAHs is the largest.Under the same amount of TW 80,a single rinse is recommended.When TW 80 and MC were employed to wash PAHs and heavy metals in the multi-contaminated soil,the results showed that TW 80 played a significant role in remov-ing PAHs,while MC was the main washing agent to remove the heavy metals.Whether TW 80 and MC are used simultaneously,or they are added one after another,there is mutual influence.In order to avoid the mutual influence of the two eluents on the removal of target pollutants,a water washing process is added.The results showed that the total removal effciency of PAHs is19.05% by adding TW 80,after by water washing three times,and then adding MC,and by water washing three times one more,which is 3.28% higher than the without water washing treatment.For the heavy metals,the total removalrate of Cd,Pb,Cu,and Zn is 61.4,55.7,24.3,and 44.4% by the above steps,which is significantly higher than the treatment without water washing(40.8,52.0,13.4,42.2%).However,there is no significant difference in the total heavy metals removal rates(60.3,54.7,23.4,45.5%)washed by adding 0.10 mol/L MC,after by water washing three times,and then adding TW 80,and by water washing three times one more.In sum,in order to reduce the inhibitory effect of MC on the removal of PAHs by TW 80,it is recommended to wash the polluted soil by TW 80 to remove PAHs,after by water washing three times,and then add MC to remove heavy metals when we leach the coking wasteland.