Study On The Treatment Of Cyanide Gold Extraction Wastewater By Ion Flotation

Cyanide gold extraction is the most widely used gold extraction technology due to its advantages of simple process and fast gold extraction speed.The wide application of cyanide gold extraction technology inevitably produced a large amount of cyanide wastewater.Gold ore is often closely associated with sulfide minerals such as copper,iron and zinc,resulting in a high content of metal ions in cyanide wastewater,which increases the difficulty of cyanide wastewater treatment.In this paper,the simulated water samples were taken as the research object.Quaternary ammonium ion flotation was used to treat cyanide gold extraction wastewater.The effects of pH,types and dosage of quaternary ammonium salts,stirring time,types and dosage of flocculants on cyanide removal were explored.pH has a great influence on flotation effect,Cuprous cyanide complexes exhibit different morphological distribution characteristics with the change of pH.With the increase of pH,the removal of cuprous cyanide complex ions becomes worse.Selection tests of quaternary ammonium salts showed that the foaming ability of long-chain quaternary ammonium salts were weaker and the association stability with cuprous cyanide complex ions were better.Quaternary ammonium salts and zinc cyanide complex ions association stability was poor,only double-chain quaternary ammonium salt and zinc cyanide complex ions could form insoluble association compounds,so copper ion complex with free cyanide was selected.It was found that the addition of organic flocculants worsed the removal of copper cyanide complex.At low concentration,inorganic flocculants promoted the removal of copper-cyanide complexes,but at high concentration,the removal of copper-cyanide complexes become worse.CTAB and DDAC were selected as roughly selected collectors and scavenging collectors respectively.After one roughing and two sweeping flotation,the contents of residual copper and total cyanide in the solution were 10.57 mg/L and 39.03 mg/L,respectively.The removal of copper and total cyanide were 94.78%and 88.78%,respectively.Some cyanide can not be removed after flotation,the calculation showed that 90%of the cyanide was HCN.On the basis of simulated water samples,the interaction mechanism between quaternary ammonium salt and copper cyanide complex was analyzed by solution chemical calculation,particle size analysis and infrared spectroscopy analysis.Solution chemistry calculation shows that at pH=5,the dominant component is Cu（CN）₂^-.With the further increase of pH,the contents of Cu（CN）₃^2-and Cu（CN）₄^3-gradually increased.When the pH is greater than 8,Cu（CN）₃^2-become the dominant component,indicating that the stability of the association formed by quaternary ammonium salt and cuprous cyanide ion is in turn Cu（CN）₂^->Cu（CN）₃^2->Cu（CN）₄^3-.Particle size tests showed that double-chain quaternary ammonium salts had better association effect and larger particle size.The determination results of copper content in association compounds showed that the copper content in the associates decreased with the increase of pH,indicating that the contents of Cu（CN）₃^2-and Cu（CN）₄^3-increase gradually,which was consistent with the solution chemical calculation results.Infrared spectrum analysis showed that the cyanide group absorption peak appeared at 2114 cm^-1,indicating that the quaternary ammonium salts reacted with cuprous cyanide complex ion.The results of flotation tests of actual wastewater showed that ion flotation can remove copper,iron,cyanide and thiocyanate to a certain extent.When oleic acid dosage was 0.1168 g/L,the removal efficiency was the best.The concentrations of copper,iron,cyanide and thiocyanide were 80.9 mg/L,90.2 mg/L,169.5 mg/L and 0.81g/L,respectively.The removal rates were 78.37%,41.69%,80.92%and 60.62%,respectively.Ion flotation is not ideal for the treatment of actual wastewater,mainly because of the high ionic strength in the actual wastewater,on the one hand,the carbon chain of quaternary ammonium salt was curled,which reduces the hydrophobicity of the association complex;on the other hand,the distribution of cuprous cyanide complex ions was changed,and the association effect between quaternary ammonium salts and copper cyanide complex deteriorated.This paper contains 29 drawings,23 tables and 97 references.