Study On The Fixation Of Potassium Ferrate On Soil

At present,chemical curing stabilization technology has been widely applied to the remediation of contaminated soil.For the alkaline soil in the north,most of the heavy metals in the alkaline environment are in a relatively stable state.However,due to the diversity of its valence state,heavy metal chromium in the soil will be in a variety of forms,especially in the alkaline environment is very unstable,which is easy to migrate and then pollute the groundwater.Therefore,in order to reduce the mobility of chromium in the soil,it simulated chromium pollution of soil,to which K₂FeO₄ fixative,to study its adsorption and desorption of chromium in the soil,and the following main results was achieved.1.It was refered to "Soil Environmental Quality Standard"?GB15618-2008?to simulate chromium contaminated soil.The adsorption performance of soil to heavy metal chromium under different pH,temperature,reaction time,K₂FeO₄ dosage and Cr???initial concentration was studied by single factor experiment,and the isothermal adsorption curve and thermodynamic equation were used to simulate the adsorption.The results showed that the adsorption capacity of Cr???increased with the increase of K₂FeO₄ dosage,and the adsorption capacity reached the maximum when the dosage was 400 mg · kg-1.The adsorptioncapacity of Cr???increased with the increase of pH.When the pH was 9-10,the adsorption capacity reached the best,the pH continued to increase,and the adsorption capacity decreased.The adsorption of Cr???on the soil after adding the fixative was the endothermic reaction.The langmuir adsorption model and the Freundlich adsorption model were used to simulate the experimental results,and the two fitting correlations were relatively high.Langmuir adsorption model showed that K₂FeO₄ increased the adsorption capacity of Cr???in soil,while Freundlich adsorption model showed that K₂FeO₄ improved the adsorption capacity of Cr???.The adsorption process was fitted by the kinetic equation.The results show that the quasi-second-order kinetic equation can reflect the adsorption process,which indicates that the adsorption process is chemical adsorption.2.The effects of natural conditions such as p H,temperature,reaction time,dosage of K₂FeO₄ and water content on the adsorption of Cr???in soil were studied by orthogonal experiment.After analyzing the experimental results,it was found that the effect of the factors on the adsorption effect of the original soil samples was pH> water content> temperature> reaction time.The optimum adsorption conditions were pH of 6.0,water content of 70%,temperature of30?,reaction time of 5h,and the adsorption capacity of Cr???was 0.1741 mg · g-1 under the optimum adsorption conditions.The amount reached43.53%.The effect of adding K₂FeO₄ soil samples on the adsorption effect was Fe6+ dosage> pH> water content> temperature> reaction time.The optimumadsorption conditions were Fe6+ dosage of 400mg·kg-1,p H value of 8.4,water content of 70%,temperature of 25 ?,reaction time of 6h.The adsorption capacity of Cr???under the optimum adsorption conditions was 0.3765mg·g-1,that is,the relative adsorption capacity was 94.13%,which was 50.6% higher than that of the original soil.3.The effects of natural conditions such as p H,initial moisture content,temperature and time on the desorption of Cr???in the original soil samples were studied by orthogonal experiments.The results showed that the effect of Cr???on the desorption conditions was pH> leaching time> initial moisture content> temperature.The optimum adsorption conditions were pH of 8.4,water content of 70%,temperature of 30?,reaction time of 5h.Under this condition,the desorption amount of Cr???reached 0.2031 mg · g-1.The minimum desorption conditions were pH of 4.2,the initial moisture content of 30%,the temperature of 20 ?,and the leaching time of 2h.Under this condition,the desorption amount of Cr???reached 0.1327mg·g-1.4.The effects of pH,initial water content,temperature and time on the desorption of Cr???in K₂FeO₄ soil samples were studied by orthogonal experiments.The results show that the effect of Cr???desorption process on soil samples was pH> initial moisture content> leaching time> temperature.The maximum desorption condition of Cr???were pH of 4.2,the initial moisture content of 9%,the temperature of 15 ?,the leaching time of 6h.Under this condition,the desorption amount of Cr???was 0.0853mg·g-1.The minimumdesorption conditions were pH of 6.6,initial moisture content of 30%,temperature of 20?,leaching time of 2h.Under this condition,the desorption amount of Cr???was 0.0048mg· g-1.Compared with the original soil samples,Cr???desorption capacity decreased by 30.9% on average,which indicated that K₂FeO₄ improved the fixation effect of soil on chromium,and thus prevented the pollution of groundwater by heavy metal chromium.