Research On Leaching Residues In Sulfur Dioxide Reduction Leaching

Zinc is an important metal material used in industry,transportation and other industries.With the rapid development of China's economy,the demand for zinc metal is increasing.Zinc smelting in China mainly adopts hydrometallurgical process.A large amount of zinc leaching residue is produced every year.The leaching residue contains a large number of valuable metals such as zinc,iron,copper and indium.If it can not be properly treated,it will cause waste of resources and environmental pollution.It is of great significance to realize efficient recovery and harmless treatment of leaching residue.In this paper,the leaching residue in zinc smelting system is taken as the research object,and the experiment of leaching residue in reduction leaching under sulphuric acid-SO₂system is carried out,which not only makes the valuable metals in the slag recovered efficiently,but also creates favorable conditions for subsequent iron removal process.The research contents and results are as follows:(1)According to the thermodynamic theory,the potential-pH diagrams of SO₂-Zn Fe₂O₄-H₂O(105?)system,Cu-As-H₂O(105?)and Cu-S-H₂O(105?)system.Thermodynamic conditions of zinc ferrite leaching and thermodynamic conditions of various forms of copper substances were defined.The reduction leaching method can effectively reduce Fe³⁺to Fe²⁺in solution,reduce solution potential and promote the decomposition of zinc ferrite.At the same time,the effect of iron ion concentration in solution on the leaching behavior of copper is obtained.(2)The effects of reaction temperature,liquid-solid ratio,initial sulfuric acid concentration,partial pressure of SO₂and stirring speed on leaching rate of medium leaching residue under sulfuric acid-sulfur dioxide reduction conditions were studied.The leaching rates of zinc95.24%,iron98.66%and indium95.04%and copper0.036%in medium leaching residue can be obtained under the conditions of reaction temperature 105?,liquid-solid ratio 8:1,initial sulfuric acid concentration 120 g/L,SO₂partial pressure 200 k Pa and stirring speed 500 r/min.Controllable extraction of valuable metals can be achieved by changing the initial sulfuric acid concentration and other experimental conditions.The comprehensive experimental results of zinc electrolyte from industrial hydrometallurgy show the feasibility of the experimental results.(3)The final residue of reductive leaching was leached under oxygen pressure to further extract copper.The efficient recovery of valuable metals was achieved under the conditions of liquid-solid ratio 10:1,temperature 105?,rotating speed 400 r/min,oxygen partial pressure 0.3 Mpa,initial sulfuric acid concentration 112 g/L and reaction time 90 min:Zn92.83%.Fe96.82%and Cu85.1%respectively.The leaching residue was leached by two-stage leaching,which not only improves the leaching rate of valuable metals,but also increases the iron content in the solution,which is mostly Fe²⁺.(4)The leaching behavior and kinetics of zinc and indium in the process of reductive leaching of medium leaching residue were studied in accordance with the second-order reaction equation and apparent activation energy 21.72 k J/mol.The leaching rate of zinc and indium can be increased by increasing initial sulfuric acid concentration,SO₂partial pressure,liquid-solid ratio,stirring speed and reaction temperature.The leaching rate can reach a stable state in about 60 minutes.