Recovery of zinc and nickel from spent catalyst
|School||Kunming University of Science and Technology|
|Course||Physical Chemistry of Metallurgy|
|Keywords||spent catalyst zinc nickel pressure leaching extraction recovery|
Spent catalyst contains many valuable metals. It can lead to resource waste and environmental pollution if it is dealt with by landfilling. Therefore, to recovery those valuable metals from spent catalyst can have great economic, social and environmental benefits.The advance on treating spent catalyst contains zinc or nickel and the separation method of zinc and nickel were introduced in this thesis. The various factors, such as leaching, extraction, back-extraction and saponification were analyzed theoretically. The method of recovering zinc and nickel from spent catalyst is by leaching-pressure leaching-solvent extraction, and back extraction were studied. Most zinc and nickel were extracted into solution under normal atmosphere. The residue was pressure leached to increase the leaching ratio of zinc and nickel. Zinc and nickel contained in solution obtained by neutral leached were separated by extraction and back extraction with P204 and 260# kerosene.Factors which affect the leaching ratio of zinc and nickel were achieved by orthogonal experiments with the following orders:the final pH value, temperature, liquid-solid ratio, stirring speed, leaching time. The optimum conditions for leaching zinc and nickel were pH=2.00, temperature was 70℃, time was 50min, stirring speed was 300rpm, liquid-solid ratio was 5. In aforementioned conditions,98.63%Zn,66%Ni leaching ratio could be obtained, and the content of zinc and nickel in leached residue was 2.12% and 12.52%, respectively.The leached residue contains 3.05%Zn and 12.48%Ni was studied by pressure leaching. The optimum conditions were pH=0.98, temperature was 150℃, stirring speed was 500rpm, time was 60min, pressure was 0.7MPa, liquid-solid ratio was 5. At the optimum conditions, the leaching ratio of zinc and nickel was 99.54% and 99.15%, respectively, and the content of zinc and nickel in leached residue was 0.05% and 0.38%, respectively.Zinc extraction was studied from the neutral lixivium with 18.19g/L Zn2+ and 6.67g/L Ni2+. The optimum conditions was 30%P204, O/A=1, pH=2.76, time was 10min, temperature was 20℃. In this condition, the extraction ratio of zinc was 99.34%. The back-extraction about load of zinc organic phase was conducted, the optimum conditions for Zn back-extraction were stripping acidity 5mol/L, O/A=6, time was 10min, temperature was 20℃. And the back-extraction ratio of Zn was 99.79%. The content of Ca2+, Fe3+, Mg2+, Ni2+ and Zn were 0.81g/L,9.39mg/L,0.29g/L,0.16g/L and 109.02g/L, respectively.Extracttion nickel studying was conducted with Zinc extraction liquid feedstock. The optimum conditions were 30% P204+70% kerosene,time was 10min,O/A=l,pH=6.1, temperature was 20℃. In this condition, the extraction ratio of nickel was 99.16%. The back-extraction about load of nickel organic phase was conducted, the optimum conditions for nickel back-extraction were pH=1.7, O/A=25, time was 10min, temperature was 20℃. And the back-extraction ratio of nickel was 99.58%.Under the aforementioned optimum conditions, the total recovery ratio of Zn, Ni can be reached to 99.58%,98.82%, respectively by closed experiment about leaching, pressure leaching, solvent extraction and back extraction. The content of Zn, Ni in leached residue was 0.02%zinc,0.32%nickel, respectively. Slag ratio was 18.34%. And the content of Zn and Ni in Zn/Ni back-extraction solution was 122.01g/L and 72.00g/L, respectively.