Research On Risk Assessment And Treating Technology Of Cyanide Wastewater

As a highy toxic substance, Cyanide presents more risk to human health in long-term exposure. To quantify the risk of the cyanide wastewater on human health, the average health risk value is acquired through the mathematical models of the non-carcinogenic health risk assessment and the Crystal Ball calculation software. In order to remain below the acceptable level for the human health risk value, the human health risk value is derived through exposure dose from huma n body contact directly and the inhaled of the cyanide. Based on the risk sources additivity, the limitation of the cyanide concentration in the water is 10-5~10-6mg/L and the cyanide steam concentration in the air remains at 0.001~0.009mg/m3.There is no ecological risk in the whole water ecology when the cyanide concentration in the water is 0.166mg/L. There is no ecological risk in the whole soil ecology when the cyanide concentration in the water is 0.148mg/L.Through researching the particle structure and solution feature, the stability order of metal complexes:Cuprous cyanide complexes>Ferric iron cyanide complexe> Ferrous iron cyanide complexes >copper cyanide complexes> Zinc cyanide complexes. In the low concentration of cyanide waste water,the main form of cyanide is three cuprous cyanide complexes,with the increaseing concentration of cyanide waste water,the main form of cyanide are three cuprous cyanide complexes and four cuprous cyanide complexes,at last is four cuprous cyanide complexes.In allusion to the characteristics of the cyanide wastewater, the cyanide wastewater was treated by emulsion liquid membrane method using three octyl amine as carrier, kerosene as membrane solvent, liquid paraffin as membrane additives, and Na OH solution as aqueous phase. It was found that the effect of each single factor on the overall removal degree of cyanide in waste water by emulsion liquid membrane method was as follow:NaOH> Span-80> emulsion to water ratio >TOA. The experimental results show that when the TOA volume fraction is 2%, the surfactant Span-80 volume fraction is 3%, the liquid paraffin volume fraction is 1%, the mass concentration of NaOH in the internal phase is 2%, the volume ratio of oil to internal phase is 1:1, the volume ratio of emulsion liquid to wastewater is 1:7 and the extraction time is 15 min, the extract rate of cyanide can reach above 95%. The actual value and the analog value fitted well by optimizing of Span-80, TOA, NaOH and ratio and other factors.