Study In Reduction-Roast Leaching Manganese From Low-Grade Manganese Dioxide Ores Using Bagasse As Reductant

A pyrometallurgical pre-treatment followed by hydro-metallurgical processing plays an important role in the treatment of low grademanganese ores. Coal’is used as reductant in traditional technology in order to convert manganese dioxide to manganese oxide which can be leached by sulfuric acid. But this method requires over800℃as reaction temperature, which will consume much energy, In addition, this kind of method produces a great deal of smoke-dust, oxysulfide, and so on, which pollute environment greatly. So it is necessary to develop a new technique to replace traditional technology, which can decrease energy consumption and pollution, but increase the utilization ratio of resources. As we know, bagasse is the fibrous residue from sugarcane juice extraction, which is a abundant renewable and inexpensive resource. In this paper, bagasse was used as reductant for reduction roasting of low-grade manganese dioxide ores under oxygen-free conditions, and the roasted ore was further leached by sulphuric acid. the effects of roasting and leaching condition on the leaching recovery、the reaction mechanism and the kinetics reaction were investigated.First of all, the effects of reduction roasting-leaching process parameters on the recovery of Mn were studied by single factor experiment design, then a statistically-based optimization strategy has been used to optimize the process parameters using response Surface Methodology. The results showed that the linear effectsand the quadratic effects of roasting temperature and weight ratio as well as the interactions between roasting temperature and roasting time were statistically significant, while the linear effect and the quadratic effect of roasting time as well as the leaching process parameters are insignificant. The model is valid and plausibly fits the experimental data with a determination coefficient (R2)of97.29%. The optimum experiment parameters were found as follows:weight ratio of0.09, roasting temperature of450℃, d roasting time of30min, leaching stirring speed of100r/min, sulfuric acid concentration of3mol/L, and leaching temperature of50℃for40min. The recovery of manganese reached98.18%under this optimal condition.The mechanism of reduction reaction were investigated by TG-FTIR and Py-GC/MS, the result showed that the substances of hydrocarbons, alcohols, aldehydes, acids, and etc, which are produced through the bagasse pyrolysis, play an important role in the process of reduction reaction. And the reduction reaction of bagasse and ore were subjected to thermal analysis, showing that reduction reaction commenced at approximately350℃and was almost completed at550℃. the DSC curve of thermal analysis further confirmed the individual thermal reaction regions associated with developments of individual manganese phases during the heating and the corresponding kinetics of the bagasse reduction process were to calculate using the ABSW method. the results showed that the reduction reaction is controlled by the interface chemical reaction at350～470℃and the equation f(s)=(1-a)2can be used to describe the kinetics of reduction reaction,while the reduction reaction is controlled by the diffusion process at47～550℃and equation f(a)=3/2(1-a)2/3[1-(1-a1/3)]-can be used to describe the kinetics of reduction reaction.The activation energy (E)was calculated to be90.965kJ/mol at350～470℃and122.423kJ/mol at470～550℃respectively.