| As an important raw material for extracting rare and precious metals,copper anode slime is a by-product of the copper electrolytic refining process.It is rich in precious metals-gold-silver,platinum group metals,rare metals-selenium-tellurium,etc.The pretreatment process should be carried out to separate and recover copper,selenium,tellurium and other metals before the comprehensive recovery of rare and precious metals from copper anode slime.At present,the pretreatment process of copper anode slime mainly includes sulfuric acid roasting and oxygen pressure leaching.These two methods have the problems of precious metal dispersion,long processes and high energy consumption.Therefore,the development of a new pretreatment technology for copper anode slime and the optimization of the process flow is beneficial to industry development.Here,a new leaching method of copper or selenium from copper anode slime was developed via ultrasonic-enhanced oxidation pretreatment.The raw copper anode slime came from a copper company in southwest China.The technology of ultrasonic pretreatment of copper anode slime has been formed by using ultrasonic as an external field enhancement means and ozone,sodium persulfate and sodium chlorate as enhanced oxidation methods.The leaching rate of copper and selenium was significantly improved by ultrasonic pretreatment of copper anode slime.Precious metals are enriched by optimizing technical parameters,which is beneficial to improve the direct yield of metals and realize the efficient separation of noble and base metals.The theoretical study of ultrasonic-enhanced oxidation leaching has been carried out,which provides a theoretical basis for the industrial application of ultrasonic metallurgy The specific conclusions are as follows:1.The change law of cavitation is studied through a high-speed camera system and visual cavitation detection.When the ultrasonic power is increased from 30 W to 150 W,the cavitation degree of the system is increased by 60%;Ultrasonic is more suitable for use in heterogeneous systems,and the degree of cavitation from homogeneous to heterogeneous can be increased to 100%;In the heterogeneous phase,the mineral size is reduced from 120 mesh to 200 mesh,and the cavitation degree of the system is increased from 15% to 70%.The conclusions indicate that increasing power and refining mineral particles are beneficial for improving ultrasound utilization.2.New methods for ultrasonic-enhanced sodium persulfate oxidation leaching of copper and ultrasonic-enhanced ozone oxidation leaching of copper were proposed respectively.The variation patterns of free radicals in these two systems were studied,and it was found that the production of free radicals increased with the increase of sodium persulfate/ozone concentration.The optimum leaching conditions for these two processes were determined.The sodium persulfate system follows: ultrasonic power 400 W,sodium persulfate concentration 50 g/L,leaching time 50 min,leaching temperature323 K,sulfuric acid concentration 160 g/L,liquid-solid ratio 3:1.The copper leaching efficiency was 98.11%,and conventional sodium persulfate leaching efficiency was only63.34%.The ozone system follows: ultrasonic power 800 W,ozone flow 10 g/h,leaching time 30 min,temperature 328 K,H2SO4 concentration 175 g/L,liquid-solid ratio 3:1.The optimum copper leaching efficiency was 98.46%,and the conventional ozone leaching efficiency of copper was 50.99% under the same conditions.3.A new method of ultrasonic-enhanced sodium chlorate oxidation leaching of selenium from copper anode slime was proposed.The optimal leaching conditions were as follows: ultrasound power 150 W,sodium chloride concentration 40 g/L,sulfuric acid concentration 150 g/L,sodium chlorate concentration 60 g/L,liquid-solid ratio 5:1,temperature 313 K,leaching time 120 min,selenium leaching efficiency was 98.21%,and the leaching efficiency of conventional sodium chlorate leaching selenium was 57.46%under the same conditions.After selenium leaching,the tellurium in the leaching solution was recovered by using ultrasound as an external field strengthening method.The optimum conditions for tellurium precipitation were determined as follows: the ultrasonic power was 120 W,the amount of copper powder added was 1.2 times the theoretical value,the time was 120 min,the tellurium precipitation temperature was 95℃,and the optimum tellurium precipitation efficiency was 99.47%.4.The apparent activation energy and limiting links of the leaching reaction were determined by the study of the kinetics of the copper/selenium leaching reaction.Ultrasound reduced the activation energy of the leaching reaction,with the sodium persulfate system decreasing from 47.96 k J/mol for conventional leaching to 16.21 k J/mol;The ozone system decreased from 31.52 k J/mol for conventional leaching to6.23 k J/mol;The sodium chlorate system decreased from 37.50 k J/mol for conventional leaching to 14.88 k J/mol.Ultrasound has changed the limiting link of the leaching reaction.Ultrasound has peeled off the solid product layer or inert substance on the surface of copper anode slime.The leaching reaction is no longer controlled by solid layer diffusion and interfacial mass transfer.5.The mineralogy analysis of copper anode slime and leaching residue showed that ultrasonic enhanced the oxidation of the leaching system.In the process of copper leaching,insoluble copper was oxidized to water-soluble copper sulfate,and in the process of selenium leaching,selenium and selenide were oxidized to water-soluble selenite;Ultrasound effectively dissociates copper/selenium aggregates,exposing the coated metal for reaction.The mineral size of copper anode slime is reduced,and the specific surface area is increased.The copper/selenium leaching efficiency improved. |
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