Removal Of Magnesium Oxide From High MgO Content Ores Using Sulfuric Acid Leaching Method And Comprehensive Utilization Of The Leaching Solution

If the main gangue in nickel-copper sulfide ores or precious metals sulfide ores is serpentine transformed from primary silicate minerals, it is difficult to get a high quality concentrate with lower MgO content that is suitable for smelting by physical mineral processing only such as floatation. This thesis put forward a new method to process this kind of ores. The MgO of serpentine is dissolved by diluted sulfuric acid so as to reduce MgO content of the final concentrate greatly. The ions of magnesium and iron dissolved in leaching solution can be utilized to produce iron oxide red and light magnesium oxide comprehensively. The new method not only can overcome the difficult problem about MgO's reducing of the ores with high MgO content by flotation, but also can raise the utilization ratio of the ores greatly. Therefore, treating the ores with the new method can lead obvious economic benefit.This thesis has studied the feasibility about the new method .The thermodynamic calculation and analysis for the reactions of serpentine and all of minerals containing Fe in sulfide ores as well as copper-nickel sulfide minerals with diluted sulfuric acid have been studied. The results showed that serpentine can react with diluted sulfuric acid easily and the MgO can be dissolved completely. Carbonate and silicate of iron as well as FeO in the minerals containing Fe also would be dissolved with leaching of MgO. Pyrrhotite (FeS) would be dissolved partly, but pyrite (FeS2) and iron oxide (FezOs) could not be dissolved with leaching of MgO. Chalcopyrite and pentlandite can also not react with diluted sulfuric acid.Jinbaoshan Platinum-Palladium Mine is so far the China's largest independent platinum group metals ore deposit. However, the platinum-palladium grade in the ore is rather low, not only the dissemination particle size of valuable minerals in the ore is extremely fine, but also the composition of the ore is very complex, and the serpentine content is high to 75%, so mineral processing of the ore is very difficult. The MgO content of floatation concentrate of the ore is difficult to reduce to below 20%. It is also difficult to smelt for such a concentrate with so high MgO content. For this reason, there is still no effective method to utilize the mineral resources at the present. Based on the theoretical studies, it has been investigated systematically that Jinbaoshan platinum-palladium ore was leached by diluted sulfuric acid. The relationships between leaching rate of Mg or Fe and consistency of sulfuric acid and temperature and liquid/solid ratio as well as particle size of the sample have been tested simultaneously. The full factorial experiment of the relationship between the consistency of sulfuric acid, leaching time and leaching rate of Mg has also beentested. The test results showed that: all of the single factors mentioned above are in direct proportion to leaching rate of Mg or Fe; for leaching rate of Mg or Fe, the influence of consistency of sulfuric acid is more remarkable than that of leaching time. The most MgO in Jinbaoshan platinum-palladium ore could be dissolved by diluted sulfuric acid solution with the consistency of 25%. Because the process characteristics of the residue are improved obviously, the high quality platinum-palladium concentrate with very low MgO content ( <3%)can be obtained from the residue by floatation using simple processing and small amount floating reagent, the recovery of Pt or Pd or Cu or Ni raised obviously. Therefore, the new method processing Jinbaoshan platinum-palladium ore by leaching and residue's flotation is very effective.The ions of magnesium and iron dissolved in leaching solution can be utilized to produce iron oxide red and light magnesium oxide comprehensively. Magnesium and iron in the leaching solution can be separated by hydrolysis method of Fe +, the iron oxide red can be produced from the hydrolyte by drying and calcining, the filter solution (MgSO4 solution) can be precipitated into magnesium carbonate (basic) with sodium carbonate and then...