Study On Lignin Reduction Roasting Manganese Oxide Ore And Microwave Strengthening

Although China is abundant for manganese resources,there are many problems such as poor,fine and miscellaneous,which needs further processing before it could be used effectively.Manganese oxide ore is the main resource of manganese ore.And the key technology of comprehensive utilization is reduction pretreatment.In this paper,the industrial alkali lignin is used as the reducing agent,and the roasting of manganese oxide ore by microwave heating is adopted to achieve the leaching of manganese by sulfuric acid leaching.In addition,the effects of the reducing agent,roasting process and leaching methods on the leaching rate of manganese are investigated,and the mechanisms of microwave-assisted the reduction process of alkali lignin was studied.The main results are as follows:?1?The effects of industrial alkali lignin,coal,cellulose,dosage and heating method on manganese leaching rate were studied.The results show that the industrial alkali lignin has a good reduction effect,followed by cellulose and coal.Under the same conditions,microwave heating is 7.27%⁵8.97%higher than the traditional heating manganese leaching rate.Taking microwave as the heating method,the optimum parameters are as follows:industrial alkali lignin dosage 50%,roasting temperature 200?,holding time 5 min,sulfuric acid concentration 1.5 mol/L,leaching temperature 50?,the leaching time is 5 min.Under these conditions,the manganese leaching rate can reach 94.45%.XRD combined with SEM-EDS analysis shows that manganese is mainly in the form of MnO₂,which is a typical manganese oxide ore.Microwave heating industrial alkali lignin roasting reduction can convert high-priced manganese in manganese oxide ore into low-cost manganese MnO,Then the purpose of selective leaching of manganese was achieved by acid leaching.?2?The mechanism of microwave-enhanced alkali lignin reduction roasting manganese oxide ore was investigated by exploring the effect of nitrogen purge flow rate,open and closed system on manganese leaching rate.The results indicated that the flow rate of nitrogen purge has little effect on the leaching rate of manganese.When the flow rate was increased from 0.2 to 3 L/min,the leaching rate of manganese is only reduced by 4%.The leaching rate of manganese in combination with closed and open systems and various spectral analysis results indicate that in the process of reduction,the solid matter?biochar?produced by pyrolysis of alkali lignin plays a major role,where in OH bond,C=C and COO-of carboxylic acid in biochar are the main electron donating.The raw ore of MnO₂ was reduced to MnO by reduction roasting.TG showed that the process of alkali lignin reducing roasting manganese oxide ore conforms to the first-order kinetic equation,and increasing the percent of alkali lignin can effectively reduce the reaction activation energy and promote the reduction reaction.?3?In terms of the reduction of alkali lignin biochar,MnO₂ was used as the material to be reduced,and the preparation process of alkali lignin biochar under open system was optimized.The optimal preparation conditions were microwave power 600W,preparation temperature 300?,heat preservation 5 min.Under the optimal calcination and reduction conditions,when the amount of alkali lignin biochar obtained by the optimal preparation process is 70%,the manganese leaching rate can reach 97.74%.The FTIR characterization indicates that the main functional groups of biochar are-OH bond,-CH₂ bond,C=C bond,C=O bond,C-O-C bond,and C-H bond of aromatic hydrocarbon.When the preparation temperature is higher than 300?,the peak intensity of O-H bond,C=O bond and C=C bond is gradually weakened,which caused a lower reducibility and leaching rate.XRD showed the manganese in the ore was mainly reduced in the order of MnO₂?Mn₃O₄?MnO during the calcination reduction process.