Research On Remediation Technology Of Cyanide Polluted Soil

Cyanide is a generic term referring to all compounds containing the –CN?triple bond between carbon and nitrogen?.The stability of cyano is quite high,and existing as a whole in general chemistry reaction.Studies have shown that cyanide mainly exists in the form of complexing state in the soil,and mainly iron cyanide complex,and there basically no exists simple cyanide in the soil.Iron cyanide complex belongs to strong complex,with high stability,and its chemical properties are quite stable at ambient pressure and atmospheric;And iron cyanide complex easily has strong adsorption with mineral colloids in the soil,which is bad for its degradation and removal.At present,there are many domestic and foreign research and report about the methods of removing cyanide in the waste water and these processing methods are relatively mature,mainly including physical method,chemical method,physical and chemical method,biochemical process and advanced oxidation process and so on.Compared with waste water,the researches and reports on the degradation and removal of cyanide in the soil are relatively limited,and the domestic related researches are very few.This paper studied the alkaline elution effect of cyanide polluted soil?including the artificial preparation cyanide polluted soil and the actual pollution soil?and discussed the main factors that influence the elution effect.In addition,this paper has carried on the further research on the degradation and removal methods and results of cyanide in alkaline eluant.Basing on the results of this paper,major conclusions are as follows:?1?The alkaline elution effect of artificial preparation iron cyanide pollution soil is greatly influenced by the initial pH of alkaline eluent.The alkaline elution rate increases with the increment of the initial pH of alkaline eluent.The alkaline elution rate is influenced by the stirring time of soil and alkaline eluent mixture,and generally increases with the increase of stirring time.The alkaline elution rate increases with the decrease of the solid-liquid ratio of soil and alkaline eluent mixture.The initial concentration of iron cyanide,the form of iron cyanide,the concentration of other cation and the concentration of TOC in the soil also have certain relevance with the alkaline elution ratio of artificial preparation iron cyanide soil.The research results of alkaline elution effect of the soil of former site of chemical plant are similar with the artificial preparation iron cyanide soil.According to the experimental results,determining that the best alkaline elution conditions for cyanide polluted soil are the initial pH value of 13,stirring time of 2 h,and solid-liquid ratio of 1:5,and cyanide elution rate could reach to 100% with these alkaline elution conditions.?2?Transfering the cyanide in the soil into the liquid phase by alkaline elution technology has only realized the first step of governing cyanide polluted soil.This study aimed at using ultraviolet light and UV-H₂O₂ technology in the further degradation process of cyanide of alkaline eluent obtaining in the optimal experimental conditions.The main conclusions are as follows: in the condition of UV light,the concentration of total cyanide of alkaline eluant solution of artificial iron cyanide soil gradually reduces with the increase of time slowly,but almost no obvious change.Until the reaction was carried out 120 min,the total cyanide removal rate was only about 10%.The experiment results show that the pure ultraviolet light has no evident degradation effect for the total cyanide of alkaline eluent of artificial iron cyanide soil.The concentration of WAD cyanide increases with the increasing of illumination time.When the illumination time was 120 min,the concentration of WAD cyanide reached the highest.In the condition of UV light,the concentration of total cyanide in the alkaline eluent of soil of former site of chemical plant gradually reduces slowly,but the change is not obvious.Responsing to 120 min,the total cyanide removal rate was only 31.11%.The experiment results show that the pure ultraviolet light has certain evident degradation effect for the total cyanide of alkaline eluent of artificial iron cyanide soil.The iron cyanide has gradually transformed into WAD cyanide.The concentration of total cyanide slightly decreases with increasing time,and the concentration of WAD cyanide increases,and the concentration of iron cyanide decreases.In the condition of UV-H₂O₂ reaction,the concentration of total cyanide of alkaline eluent of artificial iron cyanide soil gradually reduces with the increase of time slowly,but the effect is not obvious.Until the reaction was carried out for 4 h,the total cyanide removal rate was only about 20%.Among them,the experiment results show that the method of UV-H₂O₂ has crtain degradation effect for the total cyanide of alkaline eluent of artificial iron cyanide soil.The concentration of WAD cyanide of the alkaline eluent increases with the increases of illumination time.When the reaction time was 4 h,the concentration of WAD cyanide reached the highest.The concentration of WAD cyanide of alkaline eluent of soil A-1,A-2,A-3,A-4 were 13.49 mg/L,72.24 mg/L,14.43 mg/L,65.35 mg/L respectively.In the condition of UV-H₂O₂ reaction,the concentration of iron cyanide gradually reduces with increasing time.The concentration of total cyanide in the alkaline eluant of former site soil of chemical plant gradually reduces slowly.After 4 h reaction,the total cyanide removal rate was 32.27%.The experimental results show that the method of UV-H₂O₂ has a certain degradation effect for total cyanide of alkaline eluent of former site soil of chemical plant.The concentration of WAD cyanide increases with increasing the illumination time.When the illumination time was 4 h,the concentration of WAD cyanide of alkaline eluent reached the highest 126.13 mg/L.The concentration of iron cyanide gradually increases with increasing the time.