Experimental Study On Solidification/Stabilization Of Oil-contaminated Soil With Industrial Waste Slag And Sodium Persulfate

Oil may cause leakage during exploration,development,oil and gas gathering and transmission,refining,storage,and sales,thus contaminating the soil and forming oil-contaminated soil.Oil-contaminated soil contains a large number of toxic substances,which seriously affect the health of animals,plants,and human beings,while the invasion of oil into the soil body can also lead to changes in soil engineering properties.Therefore,the research on the remediation of oil-contaminated soil has important theoretical value and practical significance.In this paper,three curing materials,industrial waste calcium carbide slag,fly ash,and commonly used curing material lime,were used for the synergistic disposal of oil-contaminated soil with the oxidizing material sodium persulfate.Optimal proportioning tests were conducted to preferably select the optimal proportion of the four materials as solidification/stabilization agent.The influence of solidification/stabilization agent on the engineering properties and toxic leaching concentration of oil-contaminated soil was investigated by mechanical test,permeation test,and toxic leaching test;the activation of oil oxidation by sodium persulfate test,X diffraction test and The mechanism of solidification/stabilization of oil-contaminated soil by solidification/stabilization agent was analyzed by sodium persulfate activation oxidation oil test,X diffraction test and scanning electron microscope test.The conclusions of the study are as follows:（1）The optimal ratios of four materials were screened out by a single admixture test and orthogonal test,and by using unconfined compressive strength,acid neutralization capacity,toxic leaching concentration,and treatment cost as the evaluation index of fuzzy preference theory method,which was 8%for lime,10%for fly ash,6%for calcium carbide slag,and 0.6%for sodium persulfate.The engineering strength and environmental stability of the oil-contaminated soil after solidification/stabilization agent treatment was improved,and the toxic leaching concentration was significantly reduced.（2）For the effect of oil content,solidification/stabilization agent dosage,and maintenance age on the cured oil-contaminated soil,it was found that:with the increase of oil content,the unconfined compressive strength,cohesive force,and compression modulus of the cured oil-contaminated soil showed a trend of increasing and then decreasing,while the internal friction angle gradually decreased,and the compression coefficient and toxic leaching concentration gradually increased;with the increase of solidification/stabilization agent dosage,the unconfined compressive strength,cohesive force and compression modulus of the cured oil-contaminated soil gradually increased.The compressive strength,cohesion,internal friction angle,and compression modulus of cured oil-contaminated soil increased with the increase of solidification/stabilization agent,while the compression coefficient and toxic leaching concentration decreased gradually;the unconfined compressive strength,internal friction angle,cohesion,and compression modulus of cured oil-contaminated soil increased with the increase of curing age,while the compression coefficient and toxic leaching concentration decreased.The permeability coefficient of oil-contaminated soil gradually decreases with the increase of oil content;the changing pattern of soil permeability coefficient is not obvious after mixing with the solidification/stabilization agent.（3）The solidification/stabilization agent is mixed into the oil-contaminated soil at the beginning,the temperature and p H of the reaction vessel increase sharply,and the sodium persulfate undergoes thermal activation and alkali activation to generate strong oxidizing radicals.Sodium persulfate and activation generated strong oxidizing radicals can oxidation reaction with oil,reducing the oil content of oil-contaminated soil.Curing oil-contaminated soil specimen molding maintenance,at this time to solidification/stabilization agent hydration reaction,hydration reaction to produce gelling material hydrated calcium silicate（C-S-H）can fill the soil pores,cement soil particles but also can wrap adsorption of pollutants.The SO₄^2-produced by the oxidation reaction and the small amount of calcium alumina generated by the curing material can also fill the soil pores and improve the compactness of the soil.Combined with the above reasons,the synergistic effect of industrial waste and sodium persulfate contributed to the increase of petroleum-contaminated soil intensity,the significant improvement of engineering properties,and the decrease of toxic leaching concentration.