Study On Remediation Of Arsenic Contaminated Soil By Mechanical Activation Of Calcium Carbonate And Strengthening Of Iron Based Materials

In recent years,a series of environmental problems have been derived along with the acceleration of our industrialization level and the rapid development of our social economy.Among them,human factors led by industrial and agricultural violations led to soil heavy metal arsenic pollution situation is increasingly serious,and soil problems such as excessive soil consumption,improper fertilizer application and other soil acidification process are increasingly aggravated,which has posed a serious threat to agricultural production and natural ecological construction.Chemical passivation technology is widely used in pollution remediation of large areas of medium and low concentration soil due to its simple operation and short repair cycle.Commonly used strong alkaline chemical conditioners such as lime will cause high p H of soil,soil compaction and poor repair stability,which are easy to cause secondary pollution problems.In order to meet the urgent requirements of soil control heavy metal pollution and ensure the safe production of agricultural products,it is important to study the soil remediation technology of fixing heavy metal arsenic pollution and acid soil conditioning.In this paper,acid soil conditioner was screened and mixed with iron based materials to optimize the technological parameters of arsenic contaminated soil improvement and remediation to obtain the best remediation effect,and the stability of arsenic in soil after remediation was studied.The main research results are as follows:（1）Mechanically activated calcium carbonate（CaCO₃）has the effect of regulating acidified soil,and the soil p H is more stable.Applying a reasonable amount of added calcium can keep the soil p H within the range of 6.5-7.5,which is the most suitable for crop growth.Compared with traditional lime treatment,it can avoid the phenomenon of soil alkaline hardening and acid recombination.It lays a foundation for the further study of fixing heavy metals in soil by mixing iron base materials to achieve a step of acid fixing arsenic.（2）Through soil culture test,zero-valent iron（ZVI）was selected from three valence iron based materials as an efficient material for fixing heavy metal arsenic.The activated CaCO₃ and ZVI were mixed to achieve a one-step acid arsenic fixing effect.When the mixing ratio is 5:1,that is,2.5%ZVI+0.5%activated CaCO₃,the improvement and restoration effect is the best after mixed application.The passivation rate is still as high as 96.05%after 50 days of passivation and restoration,and the soil p H stability is controlled within a reasonable range,showing a stable trend of long-term improvement.To sum up,the application of passivating agent mixed with mechanically activated CaCO₃ and ZVI to soil restoration can achieve the double effect of"adjusting acid solid weight"in one step,which not only effectively conditioning acid soil,but also significantly improve the passivating efficiency of fixed arsenic contaminated soil under collaborative treatment.