Recovery Of Copper Silver Gold And Cyanide From Waste Cyanide Solution With Emulsion Liquid Membrane

Emulsion liquid membrane is a potential pollution control technology based on its advantages of high efficiency,high selectively,cost and energy saving.Emulsion liquid membrane can realize the dual-effective quality of environmental protection and resource recycling based on these advantages,especially in industrial wastewater treatment.The waste cyanide solution produced in gold cyanidation plant exhibits great harmful to human health and living environment.It may also contain many valuable ingredients such as copper and cyanide complexes.The feasibility of recovering copper and cyanide from waste cyanide solution with emulsion liquid membrane has been studied in this research.The stability,extraction efficiency and transport mechanism of emulsion liquid membrane and the reaction mechnism in membrane have been investigated in this paper.Tertiary amine can extract gold and silver cyanide complex efficiently.The stability of emulsion liquid membrane(ELM)with tertiary amine as mobile carrier had been studied at first.The prepared ELMs mixing with wastewater to extract gold and silver cyanide complex to recover valued metals was used.When organic extraction agent amine is used as mobile carrier,the best technology parameters of stable ELMs were:Span 80:6%;liquid paraffin:2%;extractant N235:2%,cooperate extractant TRPO:3%;the remainder being solvent kerosene;internal stripping solution:0.1 mol/L of KOH was added with speed of 10 mL/min;ratio of A/O:1;mixing at 3500 r/min for 15minutes.A relatively stable emulsion liquid membrane with swelling and breakage below 8%had been obtained.The results of experimental prepared ELMs mixing with wastewater and the silver cyanide complex extractionshow that the emulsion liquid membrane with tertiary amine-containing as mobile carrier to recover silver and gold cyanide complexes from wastewater were feasible and the extraction rate is 40%and 50%respectively.In this research,Span80 was used as the surfactant.Lix 7820 was used as carrier.The atoleine was used as the addictive.Kerosene was used as diluent and the KOH solution was used as the internal phase.By studying the effect of different compositions on the stability of the emulsion and the extraction efficiency of liquid membrane,the optimum condition for preparing the membrane is that the volume ratio of Span 80:Lix 7820:atoleine:kerosene shoud be maintained at 5:4:2:89;And the concentration of internal phase is 0.01 mol/L KOH and the volume ratio of organic to internal phase is 1:1;The emulsion time is 15 minutes and the emulsion speed is 4500 r/min.The emulsion liquid membrane used in subsequent tests was prepared according to these conditions and the breakages of membrane was less than 5%and the swelling ratio is less than 4%.The effect of emulsion liquid membrane on the extraction of copper cyanide complex from cyanide wastewater has been studied.The optimum conditionfor copper and cyanide extraction has been determined as followings:The pH of the external phase was less than 11;The stirring speed was around about 200 r/min and the stirring time was 12 min;The volume ratio of membrane to external phase was determined as 1:1.All experiments were operated at room temperature.The copper concentration in the waste cyanide solution was reduced from 150 mg/L to 0.05 mg/L with the extraction of 99%Cu under the optimal conditions.The mixture of metal cyano complexes extracted from waste cyanide solution with emulsion liquid membrane shows a selectivity order as follows:Zn(CN)42->Ni(CN)420>Cu(CN)32->Fe(CN)64-.The presence of S2O32' shows an insignificant effect on copper extraction while the SCN" ions may potentially compete for the available extractant with copper cyanide species.The effect of anions on the extraction efficiency shows that:SCN->CN->S2O32-.The extraction kinetics of copper cyanide complex with emulsion liquid membrane was examined through differential method and the apparent activation energy.The apparent activation energy obtained by graphing method on the basis of temperature and influence of extraction reaction rate:Ea= 9.7 kJ/mol.