Hydrophobilized Modification Of Lime And Its Enhanced Immobilization Of Toxic Organic Compounds

Chemical industry accidents are frequent and the site is susceptible to toxic organic compounds of high concentration.Toxic organic compounds will dissolve and volatilize to migrate,diffuse into the air and groundwater,causing secondary pollution,thus rapid control within a short period of time is necessary.Lime is a common hydraulic binder used in solidification/stabilization of contaminated soil.However,lime encapsulation is not effective to capture high-concentration toxic organic compounds released accidentally for emergency response.Most organic compounds are nonpolar and it is hard for them to bind inorganic binders.High water content of soil will deactivate the curing agent and affect the solidification/stabilization.Therefore,the fixing ability is weak,and organic matters can easily volatilize and dissolve.The surface hydrophobilized modification of lime can enhance lime's performance to capture and immobilize toxic organic compounds.It is of great significance for the emergency treatment of soil contaminated by toxic organic compounds of high concentration under accident conditions.In order to develop rapid binders for soils contaminated by toxic organics organic compounds of high concentration under accident conditions,lime powder was hydrophobilized by stearic acid,and characterized with dispersivity tests,particle size tests,specific surface area tests,oil absorption tests,scanning electron microscopy,Fourier transform infrared spectroscopy,and contact angle tests.The contact angle was used as the evaluation index of the hydrophobilized modification.The optimum conditions for the lime modification by stearic acid were: the mass fraction of stearic acid was 1%,room temperature,and the modification time was 60 min.The contact angles of modified lime were higher than 90°.The results of scanning electron microscopy and Fourier transform infrared spectroscopy showed that stearic acid covered lime surface by physical adsorption or physical coating.Hydrophobilized modification of lime was achieved.Nitrobenzene,benzene,and phenol were selected as representative toxic organic compounds.Modified lime was used as curing agent to conduct solidification/stabilization on soils contaminated by nitrobenzene,benzene,and phenol of high concentration respectively.Volatilization rate and leaching rate were used to evaluate solidification/stabilization.The results showed that 20%(lime to soil)hydrophobilized lime and 10% raw lime(lime to soil)addition reduced volatilization by 94.44% and 88.46%,acid leaching by 99.10% and 88.11%,and water leaching by 98.51% and 59.74%,compared with the blank(with no lime addition)and the control(with 30% raw lime addition).30%(lime to soil)hydrophobilized lime addition reduced volatilization by 67.59% and 95.34%,compared with the blank(with no lime addition)and the control(with 30% raw lime addition).Modified lime has no obvious effect on the leaching of water-soluble polar organic compound phenol.Lime hydrophobilized by stearic acid could be an efficient material to capture and immobilize highconcentration nonpolar toxic organic compounds in contaminated soil.Based on the study above,a scaled production process for stearic acid-modified lime was established.A project for a ten-year production period to produce 2600 tons of stearic acid-modified hydrophobic lime per year was designed.The calculation was based on this scale of production.The cost to be invested is 2,172 yuan per ton of lime.The production process uses sealed devices equipped with dust removal device and condensation reflux recovery device for acetone gas,and the cooling water uses circulating cooling water,minimizing the emission of acetone to the environment which will cause pollution and waste of resources.