Experimental Study On Purification Of Heavy Metal Zinc In Saturated Sand Using Natural Cold Energy

Artificial freezing is a green and effective method for treating heavy metal contaminated soil,but it is difficult to be widely used in actual treatment projects due to high cost constraints;while the rich natural cold energy resources in China ’s permafrost and seasonally frozen areas are frozen The conditions have been created,so this paper takes the heavy metal zinc contaminated soil as the research object,and proposes a natural cold energy to actively restore the freezing and purification methods.Through theoretical analysis and simulation experiments,the mechanism,influencing factors,purification effect and improvement measures of freezing purification are studied in detail.First,based on the water-heat-salt migration rule and equations under soil freezing conditions,the mechanism and purification equation of natural cold energy freezing purification are obtained,and the internal factors of soil and external freezing temperature are the main factors affecting the purification rate,and It shows that the key research factors in this paper are: pollutant concentration,clay content,and cold area.Secondly,using the self-designed multifunctional freezing test system,the orthogonal test of the above three factors was conducted,and the test results of the water-heat-salt field were analyzed to finally obtain the best combination of purification: concentration 20 g / L,clay content 0% The cold area is 4πcm2;at the same time,the single factor test is used to analyze the influence mechanism of the three factors on purification,and further prove the best combination obtained.Furthermore,according to the soil environmental quality standards and the Nemero index method,the natural cold energy can be frozen and purified at a time from the maximum purification rate,the effective purification height,the number of effective purification points,and the level of soil pollution after purification.Contrast horizontal freezing,clarify the limitations of its purification effect,and propose improvement measures for the overlying soil layer.Finally,carry out the purification test of the overlying soil layer and analyze its impact on the water-heat-salt field.The concentration redistribution,freezing rate and purification rate of each point of the contaminated soil after purification have fully demonstrated that the use of natural cold energy can be covered by Insulation layer method to adjust the freezing rate of contaminated soil layer to achieve better purification effect.There are 95 papers,28 tables,and 100 references.