Cyanide Wastewater With High Density Copper Treated By Precipitation Process

The cyanide wastewater with high copper content from the Henan gold smelter wasused as raw materials in this experiment.The cyanide wastewater was treated byprecipitation process and the precipitation procedure and influencing factors wasfocused on. simultaneously, the basic theoretical calculations about precipitationprocess was researched, the mechanism about the precipitation process was furtherinvestigated.On the basis of systematic analysis about composition and characteristics of thecyanide wastewater and chemical reactions that may occur in this system, thepotential-pH diagram of Cu/Zn/Fe/Au-CN-H2O system under standard conditions wasdrawn with the calculated by the relevant thermodynamic data. Laid the theoreticalfoundation for the zinc sulfate precipitation process. when3.5g ZnSO4was added to100ml cyanide water, stirred at room temperature for40minutes, iron ions, copperions and free cyanide precipitation rates reached up to100%,86%and99.34%.Precipitation process have no affection on the gold and the treated wastewater can berecycled back to the system directly. The precipitate was analyzed by XRD and itfound that the precipitate was mainly composed by Zn2[Fe(CN)6], Zn(CN)2and CuCN.The theoretical calculations of precipitation process show that actual concentration ofions is higher than the theoretical in the treated waste water and the order ofprecipitation of ions is zinc ion, copper ions, iron ion and free cyanide in proper order.Kinetic studies showed that the dynamics of precipitation process of copper ions and free cyanide are in line with the secondary kinetics model of chemical reactions andtheir rate constants were3.492dm3/(mol min) and1.387dm3/(mol min).The precipitate from the treated wastewater by zinc sulfate precipitation process wasused as raw materials in the zinc separation experiment. The influence of zincseparation on the sulfuric acid concentration, time, temperature, and the solid-liquidratio was investigated. It showed that when the solid-liquid ratio was5:1, the sulfuricacid concentration was5%, the stirred temperature was at room, the stirred time was30minutes, the dissolution rate of zinc in the precipitate reached up to90.45%,recycling quality of sodium cyanide was close to1000mg from10gprecipitate. The influence of separation of copper on the ammonia concentration, time,temperature, and the solid-liquid ratio was investigated in the copper separationexperiment. It showed that when the solid-liquid ratio was25:1, the ammoniaconcentration was25%, the stirred temperature was at room temperature, the stirredtime was90minutes, the dissolution rate of copper reached up to94.89%.The ultrafinecopper powder was preparated by reduction of the copper ions in the ammoniumchloride using hydrazine hydrate. It showed that when the hydrazine hydrateconcentration was4.5mol/L,the stirred temperature was at70℃, pH value is10, thestirred time was60minutes, the precipitation rate of copper was over98%and theparticle size of copper powder prepared was one micron.