Study On The Effect Of Additives On The Ammonia Leaching Process Of Siderite

Manganese is a kind of important basic material,which has been widely used in iron and steel,nonferrous metals,batteries and other fields.Lean ores are the main type of manganese ores in China,the average grade of manganese is only about 20%.With the rapid development of manganese industry,the demand of manganese grade are gradually increased during the process of modern production.However,the amount of medium and high grade manganese ore are too little to meet the requirements of industry.Therefore,Using advanced technology improving low grade manganese ore to prepare the high grade manganese are of great significance.At present preroasting ammonia leaching method is commonly used to improve the manganese content of the manganese ore.This process not only has good impurity removal effect,but also is friendly to environment.Compared with traditional direct acid leaching process,the leaching rate of Mn in ammonia leaching is low.In order to improve the leaching rate of the leaching process,many scholars have done a lot of research on the mineral leaching process of additives.However,the ammonia leaching process of siderite has not been studied under the condition of additives.Therefore,for the problem that the leaching rate of manganese is low while preroasting ammonia leaching is used to treat low grade magnesite.The effect of additives on ammonia leaching process of siderite is mainly studied in order to improve the leaching rate of Mn.Also the topic provides theoretical guidance for ammonia leaching process of siderite with additives.In this study,this rhodochrosite is used with the method of chlorination roasting,ammonia leaching and evaporation.The effects of two kinds of additives including ammonium hydrogen fluoride and complexing agent(EDTA,NTA^3-,gly^-and cit^3-)on the leaching rate of Mn were studied respectively.And the influence of different additives on ammonia leaching process was explained from two aspects of thermodynamics and experiment.The conclusions are as follows:?1?The X-ray fluorescence analysis and X-ray diffraction analysis were used to study the original ore and calcined manganese ore.The results showed that the manganese grade of rhodochrosite is 17.83%,which belongs to the typical low grade rhodochrosite and main phase includes MnCO₃,CaMg?CO₃?_2,SiO₂ and small amount of FeCO₃.And the results showed that the manganese grade of calcined manganese ore is23.19%,which belongs to the typical low grade rhodochrosite and main phase includes MnO,CaMg?CO₃?₂,SiO₂ and MnSiO₃.?2?The thermodynamic calculation of ammonia leaching process without additive was carried out,the results is showed that in the process of ammonia leaching,when the concentration of Mn²⁺is determined,the stable existence range of Mn?NH₃?_m²⁺would increase with the increase of the concentration of ammonia.When the ammonia concentration is determined,the smaller the concentration of Mn²⁺is,the larger the stability range of Mn?NH₃?_m²⁺will be.The thermodynamic calculation of ammonia leaching process with different additive was carried out,the addition of ammonium hydrogen fluoride does not form complexes with Mn²⁺;When the amount of EDTA,cit^3-,NTA^3-and gly^-is added into the ammonia leaching process,Mn?EDTA?^2-,Mn₂?cit?₂?OH?₂^4-,Mn?NTA?^-and Mn?gly?₂ can be formed respectively,therefore,the leaching of manganese is strengthened.?3?The influence of ammonium hydrogen fluoride on the leaching rate of Mn during ammonia leaching is investigated in this chapter:The leaching rate of Mn increased by 7%compared with that without addition of ammonium hydrogen fluoride.When ammonia leaching temperature of 30?,the ammonia concentration is 14mol/L,ammonium hydrogen fluoride dosage is 6%,ammonia leaching time is 60min,liquid-solid ratio is 6:1,stirring rate is 400r/min,the leaching rate of Mn was 91.6%.?4?The influence of coordination additives(EDTA,cit^3-,NTA^3-and gly^-)on ammonia leaching process of roderite calcined sand was studied,the results show that:the effective sequence of complexing agents are:EDTA>NTA^3->gly^->cit^3-;EDTA can improve the leaching rate of Mn in the process of ammonia leaching of calcinite when the ammonia concentration is 14mol/L,EDTA dosage is 0.05mol/L,leaching temperature is 32?,leaching time is 1h,ratio of liquid-solid is 6:1,the leaching rate of Mn increased by 5.6%from 84.5%?without EDTA?to 90.1%?with EDTA?.?5?The mechanism of enhanced Mn leaching of different additives?ammonium hydrogen fluoride and EDTA?was studied.The result shows that the process of manganese leaching can be enhanced by both ammonium fluoride and EDTA.Fluorine has erosive effect on manganese silicate,then the Mn²⁺concentration of the solution was increased,the leaching rate of Mn was finally increased.The enhanced Mn leaching of EDTA is due to the formation of Mn?EDTA?^2-.?6?The ammonia stripping process of leaching solution with ammonium hydrogen fluoride was studied,and the results show that the manganese grade of manganese carbonate obtained by steaming ammonia approach 44.13%after adding ammonium hydrogen fluoride,which has reached the requirements of the first class of HG/T4203-2011.The conditions of ammonia evaporation are:ammonia evaporation temperature is 93?,ammonia evaporation time is 60min,and the precipitation rate of Mn can reach 97.31%.