Study On The Treatment Of Cyanide Wastewater By Persulfate Oxidation

Cyanide wastewater contains a large amount of heavy metal cyanide complex ions and sulfur cyanide ions,which will cause harm to the ecological environment and life safety if discharged directly without treatment.Persulfate Advanced oxidation process has attracted great attention in the field of wastewater treatment because of its ability to produce sulfate radical with high activity and strong oxidation.This article uses persulfate oxidation technology to treat high concentration cyanide gold extraction wastewater containing copper,iron,and zinc.The focus is on studying the oxidation process and its influencing factors,exploring the removal law and reaction mechanism of cyanide and heavy metal ions.The research results have guiding significance for the comprehensive treatment of cyanide wastewater.The results show that the cyanide wastewater containing copper,iron,zinc cyanide complex ions treated by persulfate oxidation is conducive to cyanide removal by controlling the p H value in the range of 4.5～9.3.The oxidation process of copper-cyanide complex ions conforms to the first-order kinetic model,mainly based on diffusion control steps,and the apparent activation energy（Ea）is 2.76 k J/mol.Under the conditions of sodium persulfate addition amount of 0.084 mol/L,oxidation time of30 min,temperature of room temperature and p H of 12,the removal rates of CN_T,CN^-and Fe,Cu and Zn ions were 89.2%,100%,97.4%,92.7%and 42%,respectively,and the metal ions finally existed in the form of Zn₂Fe（CN）₆,Cu SCN,and Cu₂Fe（CN）₆.The removal process of cyanide is the result of the combined action of direct persulfate oxidation and free radical oxidation of SO₄^·-and·OH produced by activation.Persulfate stepwise oxidation system at room temperature,reaction time of 30 min,original p H,sodium persulfate addition amount of 0.031 mol/L,the removal rate of zinc ions was90.21%,and the precipitation was mainly Zn（CN）₂and Zn₂Fe（CN）₆.When the filtrate was added at room temperature,the reaction time was 30 min,the original p H,and the addition amount of sodium persulfate was 0.042 mol/L,the copper ion removal rate reached a maximum of 93.35%,and the precipitation was mainly Cu SCN and Cu₂Fe（CN）₆Fe²⁺cooperates with persulfate oxidation system to treat cyanide wastewater at the addition amount of sodium persulfate of 0.063 mol/L,the addition amount of Fe²⁺was0.089 mol/L,the oxidation time was 20 min,the removal rates of CN^-,CN_T,Cu and Zn could reach 100%,95.5%,98.8%and 93.1%,respectively,and the metal ions finally existed in the form of Cu₂Fe（CN）₆,Zn₂Fe（CN）₆and Cu SCN.During the oxidation process,iron ions are converted from persulfate to Fe³⁺,and the production of SO₄.^-by persulfate is catalyzed,which strengthens the oxidation ability of cyanide.The quenching experiment showed that the contribution of free radicals in Fe²⁺synergistic persulfate oxidation system was higher than that of single persulfate system,The contribution rates of SO₄^·-,.OH to CN_Tremoval were 42.04%and 14.46%,respectively.