Study Of The Extraction Of Low-grade Manganese Oxide Ore Using Biomass As Reductant

The growing demand for manganese products in industrial production results in the exhaustion of high-grade manganese ore,and therefore rationally using low-grade manganese ores is crucial to the sustainable development of manganese industry.Manganese oxide ore is an important resource.The production of manganese solution from manganese oxide ore needs to be carried out under reduction conditions,so selecting appropriate reductant is of great significance.Biomass,an abundant,renewable and environment-friendly reductant,can be used to process manganese oxide ore.However,there are some problems in the process of reducing manganese oxide ore directly by biomass,such as high reaction temperature and slow leaching speed.Based on this fact,two methods—reductive leaching with pretreated biomass as reductant and reduction roasting-acid leaching using biomass reductant were adopted to extract low-grade manganese ore,respectively.and then the obtained leaching solution was purified.This paper investigated the reaction mechanism in the reduction process,comparing the reduction effect of sawdust and straw,and examed the effect of the technological parameters on the leaching efficieney of manganese and iron.The conclusions are as follows:(1)Reductive leaching with pretreated biomass as reductant.Infrared spectrum analysis showed that concentrated sulfuric acid destroyed the biomass structure,making it hydrolyzed into monosaccharides and aromatic derivatives,among which the reducing sugar such as glucose and xylose can convert Mn2O3 into Mn2+.The reduction effect of sawdust and straw were compared,and the results showed that under the same conditions,the manganese leaching efficiency was higher with sawdust as reductant.The leaching efficiencies of 93.9%for Mn and 11.3%for Fe were obtained under the optimal conditions:stirring speed of 300 rpm,liquid/solid ratio of 5,sawdust/ore mass ratio of 0.3,sulfuric acid/ore mass ratio of 1.22,proportion of ore particle size less than 74 um of 86.2%,leaching temperature of 85?,and leaching time of 180 min.The study on the leaching kinetics indicated that the leaching process was controlled by chemical reaction.Based on Arrhenius equation,the activation energy of the reaction was calculated to be 49.1 kJ/mol.(2)Reduction roasting followed by acid leaching.XRD pattern indicated that Mn2O3 was gradually reduced,undergoing a transition from high valence to low valence:Mn2O3?Mn3O4?MnO.The reduction effect of sawdust and straw were compared,and the results showed that under the same conditions,the manganese leaching efficiency was higher with sawdust as reductant.The leaching efficiencies of 91.2%for Mn and 6.7%for Fe were obtained under the optimal conditions:sawdust/ore mass ratio of 0.3,roasting temperature of 450?,roasting time of 40 min,proportion of ore particle size less than 74 um of 92.9%,sulfuric acid/ore mass ratio of 0.81,leaching temperature of 40?,and leaching time of 90 min.(3)Purification of leaching solution.Iron was removed by ammonioiarosite method;aluminum was removed by hydrolysis method;calcium and magnesium was removed by MnF2 precipitation method;and organic matter was removed by activated carbon adsorption method.The Fe removal efficiency reached 96.2%under the conditions of pH value of 1.8,NH4HCO3 amount of 1.2 times theoretical amount,reaction temperature of 95? and reaction time of 120 min.The A1 removal efficiency of 91.8%was obtained under the conditions of pH value of 4.5,flocculant dosage of 2.5%(volume fraction),and reaction time of 120 min.The removal efficiencies of 90.2%for Ca and 85.8%for Mg were obtained under the conditions of pH value of 4.5,MnF2 amount of 2 times theoretical amount,reaction temperature of 80? and reaction time of 90 min.The removal efficiency of organic matter was 82.8%under the conditions of pH value of 4,active carbon dosage of 10 g/150 mL.reaction temperature of 25? and reaction time of 100 min.