The Interfacial Behavior Of Fe-cyanide Complexes In Typical Soil Systems With An Emphais On The Mechanisms

With the rapid development of industry,a large amount of waste gas,waste water,and waste residues are produced.According to the"National Soil Pollution Survey Bulletin",Petroleum coal,chemical medicine,mining and metallurgical industries consume a large amount of cyanide,and have the highest soil environmental standards.Due to the extremely poor mobility of the soil,the cyanide in the"three wastes"eventually migrates to the soil,causing long-term harm to the soil environment.In this paper,soils from different sources were used as cyanide adsorbents.Alkaline washing and sequential extraction were used to study the effect of soil properties and adsorption time on cyanide morphology changes.The mechanism of cyanide migration,transformation and adsorption in different soils was characterized by fourier transform infrared spectroscopy（FTIR）.The main conclusions are as follows:（1）Soil acidity and alkalinity was the primary factor affecting the migration and transformation of cyanide.Cyanide was mainly controlled by Prussian blue precipitation,manganese ferrocyanide precipitation and soil organic matter（SOM）and inorganic minerals adsorption in acidic soil,moderately acidic soil and alkaline soil,respectively.The adsorption capacity of soil to cyanide increased with decreasing pH.The adsorption capacity of ferrocyanide for five kinds of soils was Baishan>Shapingba>Zunyi>Fengjie>Jincheng.The adsorption capacity of ferricyanide was Baishan>Shapingba>Fengjie>Zunyi>Jincheng.（2）In the adsorption system,the increase in pH was related to the specific adsorption of iron-cyanide on soil minerals and the oxidation of ferrocyanide by birnessite and amorphous manganese oxide.The factors controlling the interconversion of iron-cyanide included the oxidation of ferrocyanide by birnessite and amorphous manganese oxide and the reduction of ferrocyanide by SOM.SOM could greatly promote the adsorption of cyanide,especially ferrocyanide in the soil.SOM had a larger adsorption capacity for cyanide,but had a slower adsorption rate.The remediation of long-term cyanide-contaminated alkaline soil should focus on the influence of organic matter on cyanide.（3）According to the results of sequential extraction and FTIR,the forms of iron-cyanide were similar in soils which have similar properties.In acidic soil,iron-cyanide mainly existed as KFe[Fe（CN）₆]precipitation with an absorption peak at 2076-2080cm^-1.In weakly acidic or alkaline soils,cyanide adsorption and organic binding were the main forms,and K₂Mn[Fe（CN）₆]precipitation was detected,with an absorption peak at 2065-2067cm^-1.,respectively.The micelles by iron-cyanide&humic acid may existed and be adsorbed by the organic soil,with an absorption peak at 2046cm^-1.（4）There was no obvious loss of cyanide during the long-term adsorption of 240d.The pH and Eh of the adsorption system were related to the adsorption time and the type of cyanide.The ferrocyanide system had a higher pH than the ferrocyanide system,both of them increased with time.The Eh of the ferrocyanide system was lower than the ferrocyanide system,and gradually increased during the adsorption period.The Eh of the ferricyanide system decreased from 1d to 150d and increased after 150d.The amount of cyanide in the soil continued to increase,but the cyanide migration capacity gradually decreased.In the early stage of adsorption,both of them were dominated by adsorbed cyanide,while in the later stage of adsorption,they were dominated by organically bound cyanide.