Solidification/stabilisation Of Polycyclic Aromatic Hydrocarbons-contaminated Soil

Polycyclic Aromatic Hydrocarbons are common detected contaminants in contaminated sites.As a low cost and easy to operate technology,solidification/stabilization is widely used for remediating contaminated sites.Currently,solidification/stabilization technology is widely used in heavy metal pollution,but there's a lack of relevant technology of solidification/stabilization technology on organic contaminated sites.Based on the coking plant PAHs contaminated soil as the research object,this paper has carried on ratio optimisition and effect evaluation of solidification/stabilization agent on curing of contaminated site by solidification/stabilization technology,explored the research on synergy effect of different harding agent and stabilizing agent,and carried out the site restoration to validate the effect.In this study,First,solidification/stabilization of PAHs contaminated soil using cement and activated carbon was studied.Second,When using cement only as curing agent,the problem of its higher capacity can not be ignored,this study selected a surfactant type soil firming agent consisting of the hydrophilic group of polarity and lipophilic group of nonpolar,used together with cement to deal with the PAHs contaminated soil,with the joint use of active carbon,to achieve the safe disposal and reduce the effect of valume reduction of the solidification/stabilization product.Last,in consideration of the curing reaction just wrap pollutants,not weaken or eliminate the toxicity of pollutants,we add the persulfate oxidation to remove most of the PAHs in the contaminated soil,at the same time adding activated carbon adsorption residual PAHs and oxidation reaction generated degradation products as the main technical means in the course of research,oxidation solidification/stabilization method to treat the PAHs contaminated soil.The main results of the research are shown as follows:(1)Solidification/stabilization method can effectively reduce the content of the higher ing PAHs r(4~6rings)like benzo[a]anthracene,chrysene,benzo[b]fluoranthene,benzo[a]pyrene,and dibenzo[a,h]anthracene in the soil,and for the lower ring PAHs(2~3 rings)like naphthalene,acenaphthylene,and acenaphthene,the treatment effect is relatively poor.The leachability of PAHs increased when contaminated soil was solidified only by cement,PAHs concentrations in leachates were in the order of co-disposal scenario>acid-precipitationscenario>neutral-precipitation leachates(2)Through the study on the solidification/stabilization method use activated carbon synergistic cement,shows that the addition of activated carbon can absorb the free PAHs,then effectively reduce the concentration of PAHs in leachate.UCS of solidified/stabilized materials increased with adding amounts of cement,but not affected by the amount of AC when added no more than 2% of soil weight.(3)Study found that the reduce valume solidification/stabilization method used by organic agents has obvious effect on reducing the valume of solidification/stabilization prosuct,and the strength increasing faster than cement solidification stabilization product,can effectively shorten the curing time.The products show some advantages than the control group that without organic curing agent when curing PAHs contaminated soil under the freeze-thaw cycle,such as higher UCS,lower mass loss after soil peeling;and respect of leaching was slightly higher than that of PC group,but has not been exceeded safety standards.(4)For the research of Oxidation solidification/stabilization method has shown that As the initial persulfate concentration increased,the removal of PAHs in soil increased with increasing initial persulfate concentration,initial PC concentration,and oxidation reaction time.At an initial persulfate and PC concentration of 19.20 mmol/kg and 10% of soil weight and the reaction time was 2 h,the removal rate of PAHs reached 57.3%.Residual PAHs was mainly adsorbed by the inside of soil granules thus less available.The mechanism of PC facilitates the oxidation reaction was that PC addition can increase the pH and temperature of the system.When the soil was stabilized/solidified by 10% of PC,the leaching concentration of PAHs and TOC was significantly higher than that leached from untreated soil.Persulfate oxidation decreased the leaching concentration of PAHs but increase the leaching concentration of TOC in S/S soil.Activated carbon addition can decrease both the leaching concentrations of PAHs and TOC.Freeze/thaw durability tests shows that the leachability of PAHs was not affected by freeze-thaw cycles.The UCS of treated soil samples after 12 freeze-thaw cycles was only 49.0% of that curing for 52 days,but the UCS was still > 1 MPa.The treated soil samples can resist to disintegration during the process of freeze-thaw cycles.