Study On Solidification/Stabilization Of Heavy Metal-Organic Compound Polluted Soil

The heavy metal-organic compound polluted soil has a wide range of pollution and is difficult to deal with.This paper takes the compound polluted soil of total petroleum hydrocarbons,chloroform,1,2,3-trichloropropane,benzene,arsenic and mercury in an abandoned chemical plant area as the research object.Based on the calcium oxide-based solidification method for the remediation of heavy metal-organic compound polluted soil,in order to improve the removal effect of organic matter,the calcium oxide-activated persulfate oxidation method was studied to remediate heavy metal-organic compound polluted soil.The mechanism is discussed to lay the foundation for the practical application of heavy metalorganic compound contaminated soil remediation technology.The main research results are as follows:Remediation of heavy metal-organic composite polluted soil by curing method is cured under optimal conditions(soil particle size<2mm,curing time of 7 days,and curing agent dosage of 5%),and the leaching concentration of pollutants in the cured soil is far below the environmental safety standard limit.value,the unconfined compressive strength can reach 4.2MPa,and it can be used as roadbed filler.During the solidification process,the existing form of heavy metals was transformed from the weak acid extraction state to a more stable residue state,resulting in a large amount of mayvanadite(AFt)and calcium silicate hydrate(CSH).increase and increase.The hydration product of the curing agent effectively fills the voids between the polluted soil particles,and plays a certain role in cementation,making the overall structure of the polluted soil more stable and dense,and improving the mechanical properties of heavy metal-organic polluted soil.It can solidify heavy metal ions by sealing and adsorption,complexation and precipitation,and solidify organic substances by adsorption and physical solidification.The optimum reaction conditions for the treatment of heavy metal-organic compound polluted soil by calcium oxide activated persulfate oxidation method:the dosage of sodium persulfate is 25mmol/g,the dosage ratio of sodium persulfate and calcium oxide is 2:5,and the water-soil ratio is 3:1;Under these conditions,the existing forms of mercury and arsenic were converted from weak acid extraction to a more stable residue state,and the removal rates of chloroform,benzene,total petroleum hydrocarbons and 1,2,3-trichloropropane all reached more than 80%.All indicators of the treated soil reached the screening value of the first category of construction land.On the one hand,calcium oxide catalyzes persulfate to generate sulfate radicals and hydroxyl radicals to oxidize mercury,arsenic,and degrade organic matter.On the other hand,calcium and arsenic precipitates are formed to stabilize arsenic.The optimal reaction conditions for the treatment of heavy metal-organic compound polluted soil by calcium oxide activated persulfate oxidation method:the dosage of sodium persulfate is 25 mmol/g,the dosage ratio of sodium persulfate and calcium oxide is 2:5,and the water-soil ratio is 3:1;Under this condition,the existing forms of mercury and arsenic were converted from weak acid extraction state to more stable residue state,and the removal rates of chloroform,benzene,total petroleum hydrocarbons and 1,2,3-trichloropropane all reached 80%above.All indicators of the treated soil reached the screening value of the first category of construction land.On the one hand,calcium oxide catalyzes persulfate to generate sulfate radicals and hydroxyl radicals to oxidize heavy metals and degrade organic substances.On the other hand,mercury and arsenic are passivated through physical sealing and adsorption,complexation and precipitation.