Experimental Study On Cement Solidification/Stabilization Process Refinery Waste Contaminated Soil

Solidification/stabilization technology is an important means of treatment of industrial solid waste pollution. After decades of research, solidification/stabilization has become more mature technology to waste disposal, and successfully applied to highly toxic or highly reactive hazardous waste treatment, organic toxic substances produced by incineration, arsenic waste produced in lead and zinc smelting process, treatment of organic or inorganic toxic pollutants etc. to make pollutants into less toxic or nontoxic purposes. This paper combined site pollution of the soil contaminated by oil refinery waste, used cement solidification/stabilization treatment to contaminated soil, researched the changes in strength and leaching toxicity of contaminated soil by cement solidification/stabilization treatment under different cement content, degree of compaction and curing period and other conditions, revealed changing mechanism of engineering properties of contaminated soil by cement solidification/stabilization treatment. Results are as follows:(1)Through laboratory test researching strength characteristics of contaminated soil by cement solidification/stabilization treatment. Under the same degree of compaction and curing period conditions, with the increase of cement content, unconfined compression strength of contaminated soil by cement solidification/stabilization treatment increased with cement content increasing; Under the same cement content conditions, unconfined compression strength of contaminated soil showed an increasing state with the degree of compaction increasing, because of heavy metal ions, when the degree of compaction exceeds 0.9 unconfined compression strength shows a downward trend; Unconfined compression strength of contaminated soil by cement solidification/stabilization treatment increase s with curing period of increasing.(2)Through the study of leaching toxicity of contaminated soil, the p H of cured soil leaching has a direct correlation with cement content, with cement content increasing, the pH of cured soil leaching shows rising state. Under the same cement content, the pH of cured soil leaching in 90 d curing period is slightly smaller than in 28 d.(3)Benzene content of cured soil leaching is influenced by cement content very much, benzene content of light soil in 90 d curing period significantly lower than in 28 d curing period; Cement contains phenol, phenol content increases with cement content increasing; Chromium content increases in a certain volatility with cement content increasing, less affected by curing period; Cadmium concentration reduces with cement content increasing, the concentration has been below the concentration 0.0197 mg/L before curing, lower than the national standard limit 0.3 mg/L, curing period has little effect on the concentration of cadmium; Lead concentration decreases with cement is added; Sulphide content increases with cement content increasing, and sulphide content in 90 d curing period is higher than in 28 d.(4)After the addition of cement, the COD of contaminated soil decreases rapidly. With the increase of cement content, the changing rate of COD is not great; The BOD5 of contaminated soil decreases with cement content increasing, but there are changes in a certain volatility; The relative content of organic matter increases with cement content increasing, the concentration of leaching reduces, the concentration in 90 d curing period is obviously smaller than in 28 d.(5)The use of a scanning electron microscope(SEM) analyzes microstructure features of contaminated soil by cement solidification/stabilization treatment. Compared with cement solidification, particles edges of dry cement are sharper. With the increase of ceme nt content, there are more rod- like tissue in the combination unit of original soil and cement, the particles are tightly cemented, more concentrated, and bulk clutter. With the age greater, there are more cement gel hydration through cement producing, network organization of cement surface and newly forming rod- like tissue intertwined. Compared with dark soil, there are more rod-like tissue in the light soil. The binding extent of the light soil is better than dark soil.