| The copper anode slime is an important by-product produced in the copper electrolytic refining process and contains many precious and rare metals,which is an important raw material to extract precious and rare metals.Generally the traditional pretreatment technology of copper anode slime can be divided into four stage process:pyrometallurgy process,half hydrometallurgy process,flotation-metallurgy process and hydrometallurgy process.This technology has a few limitations such as lengthy processing time,low recoveries of valuable metals,environmental pollution and equipment corrosion.Therefore,the development tendencies of the pretreatment of copper anode slime are as follows:utilization of the advanced green technology and highly-efficient equipment,increase of productivity.improvement of the recoveries of valuable metals and reduction of environment pollution.This study aims to deal with the raw material of copper anode slime containing high nickel and high lead using the atmospheric pressure leaching,ultrasound assisted leaching.microwave assisted leaching and microwave-ultrasound assisted leaching pretreatment processes,respectively.The new technology of microwave assisted pretreatment-pressure leaching of copper anode slime has been proposed.In this technology,the weight of anode slime was reduced observably and precious metals were concentrated significantly.which is helpful in enhancing the recovery ratio of precious metals and reducing environmental pollution.Thereby,the high efficient separation of precious metals and base metals has been realized.Meanwhile,the theoretical study of microwave assisted leaching and ultrasound assisted leaching has been investigated,which is used to provide the theoretical basis for metallurgical industrial application of microwave and ultrasound technologies.In addition.recovery of valuable metals from leaching solution containing Cu,Se and Te by the process of extraction-Na2SO3 reduction has been studied.Research results show that the optimized conditions of atmospheric pressure acid leaching of copper anode slime with high nickel content are as follows:H2SO4 concentration of 1.5 mol·L-1,leaching temperature of 70?,solid-liquid ratio of 0.20 g·mL-1,leaching time of 60 min,ventilation rate of 0.2 L min-1,concentration of hydrogen peroxide of 0.3 mol·L-1 and stirring speed of 500 r-min-1.Under these conditions,the leaching efficiencies of copper,tellurium and selenium are 92.90%,67.75%and 17.34%,respectively.The optimized conditions of atmospheric pressure acid leaching of copper anode slime with high lead content are as follows:H2SO4 concentration of 2.0 mol·L-1,leaching temperature of 80?,solid-liquid ratio of 0.20 g·mL-1,leaching time of 90 min,ventilation rate of 0.2 L·min-1,concentration of hydrogen peroxide of 0.2 mol·L-1 and stirring speed of 500 r-min-1.Under these conditions,the leaching efficiencies of copper,tellurium and selenium are 94.78%,29.38%and 16.98%,respectively.The optimum conditions of ultrasound assisted leaching of copper anode slime with high nickel content are as follows:ultrasound power of 700 W,leaching time of 40 min,H2SO4 concentation of 1.5 mol·L-1,leaching temperature of 70?,solid-liquid ratio of 0.25 g·mL-1,ventilation rate of 0.3 L·min-1 and concentration of hydrogen peroxide of 0.2 mol·L-1.Under these conditions,the leaching efficiencies of copper,tellurium and selenium are 97.41%,88.23%and 33.98%,respectively.The optimum conditions of ultrasound assisted leaching of copper anode slime with high lead content are as follows:ultrasound power of 500 W,leaching time of 60 ming H2SO4 concentration of 1.5 mol·L-1,leaching temperature of 80?,solid-liquid ratio of 0.25 g·mL-1,ventilation rate of 0.4 L·min-1 and concentration of hydrogen peroxide of 0.2 mol·L-1.Under these conditions,the leaching efficiencies of copper,tellurium and selenium are 98.75%.55.23%and 35.98%,respectively.The optimum conditions of microwave assisted pretreatment-pressure leaching of copper anode slime with high nickel content are as follows,microwave assisted pretreatment:microwave power of 450 W,leaching time of 300 s,solid-liquid ratio of 0.10 g·mL-1,target temperature of 110?,H2SO4 concentration of 1.5 mol·L-1,concentration of hydrogen peroxide of 0.8 mol·L-1,stirring speed of 500r·min-1;pressure leaching:H2SO4 concentration of 3.0 mol·L-1,leaching temperature of 170?,leaching time of 120 min,solid-liquid ratio of 0.20 g·mL-1,stirring speed of 500 r?min"1.Under these conditions,the leaching efficiencies of copper,tellurium,selenium and nickel are 97.12%,95.97%,95.37%and 93.90%,respectively.A kinetic study shows that the pressure leaching of copper anode slime,with and without microwave assisted pretreatment are both controlled by chemical reactions on the surfaces of particles.It is found that the activation energy calculated for microwave assisted pretreatment-pressure leaching(49.47 kJ·mol-1)is lower than that for pressure leaching which is without microwave assisted pretreatment(60.57 kJ·mol-1).The optimized conditions of microwave assisted leaching of copper anode slime with high lead content are as follows:microwave power of 600 W,leaching time of 40 min,solid-liquid ratio of 0.30 gmL-1,target temperature of 90?.H2SO4 concentration of 1.5 mol·L-1,concentration of hydrogen peroxide of 0.6 mol·L-1 and stirring speed of 500 r·min-1.Under these conditions,the leaching efficiencies of copper,tellurium and selenium are 99.56%,78.31%and 75.44%,respectively.The process of microwave-ultrasound assisted leaching of copper anode slime with high nickel content has been optimized using response surface methodology.The optimum conditions are as follows:microwave power of 834 W.ultrasound power of 638 W and reaction time of 403 s.Under these conditions,the experimental leaching efficiencies of Cu.Te and Se are 98.88±0.56%.,98.9610,78%and 98,57±0.67%,respectively.The process of microwave-ultrasound assisted leaching of copper anode slime with high lead content has been investigated.It is found that the leaching efficiencies of Cu.Te and Se under microwave-ultrasound assisted leaching conditions are higher than that under microwave assisted leaching conditions.This can be attributed to the effect of ultrasound.The minute cracks on mineral surface of microwave-ultrasound assisted leaching residue are clearly more than microwave assisted leaching residue.which could improve the recovery of valuable metals.In addition.efficiency of leaching reaction can be enhanced,due to the unique mechanical effect.thermal effect and cavitation effect of ultrasound.The mechanism of microwave-assisted leaching system has been studied.It is suggested that the enhancement on the recoveries of valuable metals is attributed to the temperature gradient between solid and liquid,existence of microwave hyperthermal penetration area,and generation of cracks on mineral surface.The model of microwave-assisted leaching process has been put forward on the basis of SEM analysis of mineral surface under microwave condition.The mechanism of ultrasound-assisted leaching system was also studied.It is found that the activation energy calculated for ultrasound assisted leaching(40.98 kJ·mol-1)is lower than that for the atmospheric pressure leaching(53.40 kJ mol-1).This can be attributed to the cavitation effect of ultrasound.In addition,the "effect of crack" of ultrasound assisted leaching process has been confirmed on the basis of SEM analysis of leaching residue,which is beneficial to dissociate minerals and improve the recoveries of valuable metals.Recovery of valuable metals from leaching solution containing Cu,Se and Te by process of extraction-Na2SO3 reduction has been studied.The optimized conditions of extraction are as follows:initial pH value of 2.0,volume concentration of extractant(AD-100)of 20%.phase ratio(O/A)of 1:1,extraction time of 8 min.The optimized conditions of back-extraction are as follows:H2SO4 concentration of 2.0 mol·L-1,phase ratio(O/A)of 1:1,stripping time of 6 min.The optimized conditions of process of Na2SO3 reduction are as follows:Na2SO3 concentration of 1.5 mol·L-1.H2SO4 concentration of 2.0 mol L-1,temperature of 90?.reaction time of 120 min,NaCl concentration of 0.8 mol·L-1,stirring speed of 350 r·min-1.Under these conditions,the recovery rate of Cu,Se and Te are 95.87%.98.77%and 96.53%.respectively.The mass fractions of Se,Te,Cu and Ag in reduction product are 79.69%.9.12%,6.54%and 3.32%,respectively.Selenium in reduction product exits mostly in the form of elementary substance and Cu2Se,meanwhile,tellurium in reduction product exits mostly in the form of elementary substance and Ag7Te4.The efficient process of leaching-recovery to treat copper anode slime has been proposed,which combines microwave assisted pretreatment-pressure leaching process with the extraction-Na2SO3 reduction process.The leaching efficiencies of copper,tellurium,selenium and nickel increase by 11.24%.34.20%,72.23%and 25.50%.respectively.Meanwhile,the cost of production decrease due to the reduction of leaching time.In addition,the valuable metals in the leaching solution can be recovered efficiently. |
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