| Copper is one of the metals which were discovered early and used most widely by humans.Copper has become an indispensable basic material and strategic material in the fields of national economy,national defense engineering and new technology.These years,copper metallurgy technology has developed rapidly,which leads to the shortfall in supply of copper raw material and the decline in grade of ore.Cobalt and its alloy are widely used in aerospace,defense industry,chemical,electrical and new energy and other industries.There are few single cobalt deposits in nature and most of them are associated with other minerals.The secondary copper-cobalt oxide ore is one of typical cobalt associated minerals.It is difficult to process using the traditional technology due to the poor floatability and low grade.Therefore,the exploitation and utilization of secondary copper-cobalt oxide ore is very important.This work aims to recover copper and cobalt from some typical refractory copper-cobalt oxide ore in Zambia using hydrometallurgy process including leaching,solvent extraction and electrowinning.The mineral characteristics,agitation leaching with sulfuric acid,bioleaching,acid curing leaching in column and flocculation sedimentation of leaching solution have been emphatically investigated in this paper.On this basis,the industrial scale experiments have been carried out and a new hydrometallurgy process for recovery of copper and cobalt from refractory low grade copper-cobalt ore has been proposed.In addition,the sulfur metabolism model of Acidicaldus organivorus has been constructed using comparative genomics technology,bioleaching mechanism of copper-cobalt ore has been described.Study results on process mineralogy show that the mineral consists of competent ore and friable ore.The main ore includes:quartz,potassium feldspar,greenalite,magnesium tourmaline,ilmenite,bismuth oxide etc..The content of copper and cobalt is about 1%and 0.05%,respectively.The percentage of pseudo-malachite in both of them is more than 20%.The content of copper which is wrapped by limonite and exist in the biotite is above 60%.The true density of ore is 2.375 t·m-3,loose density of ore is 1.45 t·m-3,hardness coefficient of competent ore and and friable ore is 4?9 and 2?6,respectively,angle of repose for ore is 36°and ore grinding work index of friable ore is 7.66 kwh·t-1.The optimum conditions for agitation leach process are as follows:70%of the particles are less than 74 ?m size,the leaching temperature is 65 ?,initial acid addition is 45 kg·t-1,leach time is 4 h,pulp density is 30%,agitation speed is 500 r-min-1.Under these conditions,the leach efficiency of copper and cobalt is 74.34%and 43.32%respectively.The nonionic flocculant 912 has a good flocculation effect on leaching solution.Under the conditions that the pulp density is 6?8%,concentration of flocculating agent is 0.1%and addition quantity of flocculating agent is 30 g·t-1,the settling velocity can reach 5 m·h-1?21 m·h-1.The technology of curing the dumps with sulphuric acid can shorten the leaching period and improve copper leach efficiency.And the optimum conditions for column leach are as follows:particle size after crushing is<50 im,irrigation intensity is 5.3 L·m-2·h-1,period of leaching is 90 d,gangue acid consumption is 3.98 t·t-1 Cu.The copper leach efficiency by this method is 73.73%which is 10%higher than the rate without the curing process.A typical refractory low grade copper-cobalt ore was bioleached with a bacteria group of artificial microbial leaching bacteria.The specimens were compared with shaked,agitated and column leached ones by acid.The results showed that under the shaking and agitating condition,the end Cu leaching efficiency with bioleaching method under at 40 ? is about 90%,which is higher than the one of shake flask acid leaching by 21.3%and the one of mixing acid leaching by 16.3%.The end Cu leaching efficiency of biological column leaching is 90.6%,which is higher than the one of acid column leach by 5.8%.The sulfur oxidation system of Acidicaldus organivorus DX-1 bacterial strain has unique features although it is similar to the common acidophilic sulfur-oxidizing bacteria.It does not contain sulfur oxidizing bacteria,SOR which is closely related to elemental sulfur oxidation and encoding gene related to SDO which has been widely reported.The bacterium contains a HdrABC complex enzyme that can oxidize cytoplasmic sulphur.In addition,A.organivorus strain also contains the S4I pathway and the indirect sulfite oxidation pathway through APS.The expanding test results show that the leach efficiency of Cu and Co in friable ore was 80%and 75%respectively,the leach efficiency of Cu for competent ore was 72%,the extraction rate was 99%in extraction process,the recovery rate of copper in electrowinning process was 99.50%,the precipitation rate of Co was 98%and the precipitate of Co is higher than 30%in cobalt recovery process.The total recovery rate of Cu and Co for friable ore is 78.0 2%and 72.02%respectively.The total recovery of copper for competent ore is 70.92%,Based on the low grade copper-cobalt oxide ore of Zambia,the hydrometallurgical plant with an annual capacity of 40 thousand tons of cathode copper has been built using the process of leaching,solvent extraction and electrowining.Both the capacity of heap leach and agitation leach in this plant accounts for 50%.The leach efficiency of copper using intensified agitation leach technology increased to 82%.The leach efficiency of copper reached 73%after heap leach for 240 days with sulphuric acid curing process,which is higher than the leach efficiency of 65%without curing process(heap leach for 630 days).Industrial practice shows that curing technique can accelerate the leaching,improves leaching efficiency,and reduces the acid consumption.A new hydrometallurgy process for recovery of copper and cobalt from refractory low grade copper-cobalt ore of Zambia has been proposed. |
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