Study On Thermal Remediation Mechanism Of Iron-cyanide Compounds And Their Adsorption Behavior On Goethite-humic Acid Complex

With the wide application of cyanide in various industries,the total amount of cyanide input in the environment has far exceeded the self-purification range of nature itself.It mainly remains,accumulates and migrates in the soil in the form of ferricyanide and ferrocyanide.It causes pollution to the soil and groundwater environment,and poses a hazard to human health.Therefore,it is necessary to pay attention to the problem of soil cyanide pollution repair.This paper mainly conducts two aspects of research.On the one hand,it uses heat treatment technology to repair cyanide-contaminated soil,focusing on exploring the reaction path and degradation mechanism of cyanide during the heat repair process,and to quantitatively evaluate the possible secondary pollution caused by heat treatment and the negative impact on the soil properties.On the other hand,the migration and transformation of cyanide in the soil is directly related to its environmental risks,consider that cyanide in the soil tends to adsorb or precipitate through physical or chemical interactions with soil mineral components.Taking goethite-humic acid complex as a typical representative of soil mineral components,the adsorption behavior and regularity of ferricyanide ion and ferrocyanide ion on the surface of the complex were explored.The research results provide theoretical basis and support for accurately assessing the environmental behavior of cyanide in the soil system and the environmental risks it brings.The specific research is as follows:(1)Through the heat treatment experiment of K [Fe(CN)]、K [Fe(CN)] and Fe [Fe(CN)])soils,it was found that the heat treatment temperature range(200-500℃)used in this research can achieve a good remove effect,and it has little effect on soil properties.By analyzing the degradation products of cyanide during the heat treatment process,it is speculated that the degradation process of cyanide is as follows: the cyanide complex decomposes first,releasing highly toxic free cyanide(CN or HCN),and then oxidized to the intermediate product CNO,or directly oxidized to the final products CO 、CO、N and NO.(2)XRD characterization results of synthetic goethite show that it is a pure goethite system with good crystal form.The goethite-humic acid complex’s SEM characterization found that the addition of humic acid will change the surface morphology of the original mineral,the smoothing mode tends to be fuzzy,the humic acid will bridge the goethite,and there is obvious agglomeration between the needle-shaped particles,showing a massive structure.The color of the goethite surface deepens with increasing humic acid loading.The GH,GH-300 HA,and GH-600 HA were found to have isoelectric points of 9.23,9.16,and 9.08 by Zeta potential titration,the isoelectric points gradually decreased with the increase of the concentration of loaded humic acid.(3)Under different p H values and ionic strengths,as the concentration of humic acid increases,the adsorption capacity of K [ Fe(CN)] and K [ Fe(CN)] on GH-5000 HA can be reduced from 49μmol / g,64μmol / g to 13μmol / g to 30.0μmol / g respectively.The SPSS significance test results of GH and GH-2000 HA adsorption show that humic acid has a significant inhibitory effect on the adsorption of ferricyanide on goethite,while the inhibitory effect on the adsorption of ferrocyanide is slightly weaker,indicating that the adsorption of ferrocyanide on the mineral surface is more stable.(4)The K [Fe(CN)] and K [Fe(CN)] adsorption capacity of the complex decreases with increasing p H.Under acidic conditions,it is conducive to the adsorption of ferricyanide and ferrocyanide ions.When p H = 4,the adsorption capacity of the two ions is the largest,taking GH-600 HA as an example,it can reach 60μmol / g and68μmol / g respectively.At the same time,the ionic strength has a certain degree of inhibitory effect on the adsorption of ferricyanide on the composite,especially when its value reaches 0.1M,the inhibition action is more obvious,and the adsorption of ferricyanide decreases by nearly double.For ferrocyanide,the ionic strength has no significant effect on the isothermal adsorption of ferrocyanide-goethite-humic acid complex.