Acid leaching process is a kind of traditional method of recovery of zinc, but the acid leaching method in the treatment of zinc oxide ore with high acid consumption, purification filtering difficulties, problems such as heavy burden.
Therefore, the use of alkaline system to leaching of zinc oxide ore attaches great importance to by the researchers at home and abroad.
Alkaline leaching can avoid the formation of silica gel, the method is based on sodium hydroxide or ammonia salt as leaching agent + money, make zinc oxide ore of zinc in zinc acid sodium salt, or form complex ions into the process of leach liquor.
According to the use of different leaching agent into ammonia leaching method and the alkali leaching method (
Is the present study, the two types of leaching system system widely.
Ammonia leaching ammonia leaching in ammonia and ammonia mixed with the salt as leaching agent, commonly used by salt by sulfate, chloride are there press, carbonic acid, citric acid, press, etc.
Because of ammonia with special chemical properties, strong coordination ability, can with a lot of transition metal ions such as zinc, copper, nickel, drilling, such as, pot, gold and silver form the coordination compound, increase the solubility of metal ions in liquid ammonia leaching, so as to realize the leaching of metal minerals.
ammonia leaching was originally used to recovery of copper from copper oxide and natural copper, the method has been used in copper, nickel, drill, pan, the extraction of metals such as gold and silver in metallurgy.
Ammonia leaching method from acid leaching method, has the following advantages, 1) ammonia leaching leaching of metal minerals with high selectivity.
Suitable for dealing with high content of alkaline gangue mineral, ore of the impurity such as iron, silicon, manganese, calcium, magnesium, etc. Not dissolve in ammonia immersion or due to lower complexing ability can't dissolution in residue, and acid leaching method because of the high concentration of alkaline gangue lead to high acid consumption, not economic;
(2) of equipment corrosion small, ammonia leaching method is more suitable for the large-scale leaching of low grade ore and high grade ore leaching;
3. Ammonia leaching method can avoid acid leaching method of sediment formation due to pH adjustment;
(4) by using ammonia leaching processing zinc material to recovery of valuable metals, has a wide adaptability of raw material, technological process short, purify the burden is light, small environmental pollution, product variety, the characteristics of less investment, to promote progress of wet zinc smelting technology has profound significance and broad application prospect.
5. Ammonia, low toxicity, low cost, easy to get, easy to recycle is also widely used in the process of ammonia in hydrometallurgy important reasons.
ammonia leaching can achieve a higher rate, but ammonia volatile, easy to produce secondary pollution.
Zinc from the zinc oxide ore mainly ZnCO3, ZnO · SiO2 · H2O, ZnCO3 · 2 zinc (
2 and ZnO form, they are respectively smithsonite and hemimorphite, water zinc ore, the main components of zincite a money salt soluble in ammonia solution, ammonia zinc in zinc complexes form into the solution.
Main reaction are:
zinc dissolved in ammonia salt a hinge system at the same time, with ammonia complexing impurity elements such as Cu, Cd and other impurities generated ammonia complex in solution, but by adding the right amount of zinc powder metal impurities purification to electric product process requirements of critical � � the following.
But Mn, Mg, Si, Fe and other elements, it is difficult to dissolve in the leaching residue, it also reflects the salt leaching selective advantage.
the ammonia chloride leaching by system in ammonia leaching, most studied is ammonia chloride by leaching system.
Low grade zinc oxide ore with NH4Cl -
Leaching, NH3 system due to the zinc chloride and ammonia and coordination, so the solubility of zinc oxide ore is larger, metal zinc coordination with chloride ions reduce the reduction potential, increase the leaching rate of reaction, and a ammonia chloride according to the formation of the buffer system to increase the dissolution of zinc.
The system is used to leaching of zinc oxide ore already have a lot of reports.
Happy one, ryu NH3 + NH4Cl as leaching agent is given priority to with smithsonite and hemimorphite zinc oxide ore, leaching at optimum conditions, the leaching rate of zinc of 89 respectively.
3% and 87.
51% : tang, M (
System circulating leaching orchid content less than 10% of low grade zinc oxide ore, most of the leach liquor return to the leaching of zinc concentration.
Circulating leaching experiments the optimum conditions were determined as follows: liquid-solid ratio 4:1, normal temperature, stirring speed 300 r/min, 3 h leaching time, leaching agent composition for 3 mol/L NHaOH + 4 mol/L NH4Cl.
Under this condition, the average concentration of zinc in the balance after the leaching liquid for 33.
93 g/L, the zinc leaching rate for an average of 69.
08%, into the less content of impurity elements in the leaching liquid of the technology for low grade with high alkaline gangue is difficult to choose the development of zinc oxide ore is of great significance.
Zhang in the NH3 -
H2O system leaching of low grade zinc oxide ore from zinc, under the condition of optimization of zinc leaching rate reached 93.
74%, the leaching liquid transmission product after purification, electric zinc zinc is greater than 99.
999%, electrolyte fill after ammonia can be recycled, taking the process flow is as follows.
NH3 - in zinc oxide ore
H2O conventional leaching process, the introduction of ultrasonic outfield technology to strengthen the leaching process, the time required to achieve the same leaching rate reduced, significantly improve the zinc leaching rate, when the reaction temperature and concentration of leaching agent is low, the molar concentration of NH4Cl and NH4OH is larger, the reinforcement of ultrasonic radiation significantly.
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