Study On Stability And Solidification Rehabilitation Of Hexavalent Chromium Contaminated Soil

With the rapid development of economy and the frequent activities of human beings,the environmental problems tend to be severe,and the pollution of heavy metal soil caused by some heavy metal related industries has become one of the biggest environmental problems of soil pollution in the world today,and the soil six price chromium pollution in recent years has produced many problems.In order to control the soil contaminated by hexavalent chromium,six valence chromium contaminated soil was repaired and cured by FeSO4·7H2O,cement and lime,and the mix ratio of cured soil was determined according to natural background value,solubility and other factors.Based on the macroscopic test of the cured soil under different mating ratios,the mechanical properties,chemical stability,anti-freezing and thawing characteristics and curing mechanism of the cured soil were studied,and the microstructure analysis of the cured soil of six valence chromium pollution was determined by microscopic test,and the microstructure of the contaminated soil was studied.Thus,it provides engineering basis for heavy metal contaminated solidified soil as building materials in non-sensitive areas and for resource utilization of hexavalent chromium contaminated soil.The main research results are as follows:1.The potassium chromate solution and air-dried sieve of the silt loam mixed,the configuration of different concentrations of artificial contaminated soil,after different curing age solidification of the non-lateral compressive strength test,the six valence chromium ion concentration,curing age,cement blending,lime content on the strength of the curing soil effect;The stress-strain curve of solidified soil was analyzed.The dosage threshold of raw lime affecting the strength of solidified soil was put forward.2.To conduct a toxic leaching test on the cured soil of 28 days old.Exploring the effect of quicklime content on the stability of solidified soil,The single factor pollution index method was used to evaluate the curing effect.It is concluded that the toxicity leaching standard cannot be achieved under the action of only the reducing agent FeSO4·7H2O.The hexavalent chromium ion leaching concentration of the contaminated soil under the joint action of cement and quicklime is reduced.3.The freeze-thaw cycle test was carried out on the solidified soil.The macro-damage effect of freeze-thaw cycles,different hexavalent chromium ion concentration and different quicklime content on the solidified soil under the freeze-thaw cycle was investigated.The solidified soil after freeze-thaw cycle was carried out.Toxicity leaching test,the strength damage law and chemical stability law of the frozen-thaw cycle of solidified soil were obtained.4.Through the nuclear magnetic resonance test of the solidified soil,the dynamic change of its pore diameter under the freeze-thaw cycle was studied,and the relationship between porosity,strength performance,chemical stability and pore diameter was explored It is found that the pore size is mainly distributed in the range of 0.014~1.8?m,and the pore sizes of 1~1.8?m and 1.8~70?m increase the porosity of the solidified soil under the freeze-thaw cycle.The small pore size of 0.014~0.1?m increases the strength of the solidified soil and reduces the leaching.The concentration is most pronounced.5.Combined with SEM electron microscopy and ultra-depth depth test,the pore structure of solidified soil under freeze-thaw cycle was analyzed.The dynamic evolution and solidification mechanism were investigated from microscopic and microscopic.