Study On Leaching Manganese From Iron Rich Manganese Oxide Ore And Preparation Of Manganese Slag-Carbon Catalyst

Manganese is an important strategic resource and widely used in steel,alloys,batteries and pharmaceutical industries.Unfortunately,when the iron rich manganese oxide ore is leached by the two-ore method,a large amount of elemental sulfur is generated to cover the surface of the mineral particles,reducing the leaching reaction rate.Therefore,it is of practical significance and economic value to carry out research on the process of leaching iron rich manganese oxide by two-ore method.Moreover,Manganese slag has a large output,high treatment costs,and its improper disposal will cause serious environmental pollution problems.Hence,the resource utilization of Manganese slag has become an urgent problem to be solved in the manganese industry.In this paper,iron rich manganese oxide ore was used as raw material to study the leaching process of Mn using pyrite as the reducing agent and adding charcoal powder in sulfuric acid medium.At the same time,in order to solve the problem of the utilization of Mn leaching residue by two-ore method,Magnetic manganese slag-Carbon heterogeneous catalyst（MS-C）was prepared by sol-gel method and used for catalytic degradation of Rhodamine B（Rh B）and Methylene blue,the major contents are shown as follows.The wet reduction leaching process of iron-rich manganese oxide ore using pyrite as reducing agent and adding charcoal in sulfuric acid solution was investigated to optimize process conditions through single factor experiment.In the condition of 10.0 g iron-rich manganese dioxide ore,pyrite dosage 5.0 g,charcoal powder dosage 0.1 g,sulfuric acid concentration 1.36 mol·L^–1,leaching temperature 70℃and leaching time 4 h,the manganese leaching rate can reach96.7%.Thus,the low-temperature manganese leaching method from iron-rich manganese dioxide ore was obtained.The interaction between pyrite dosage,sulfuric acid concentration and charcoal powder dosage was studied by Box-Behnken Response Surface Methodology.The results demonstrated that the deterministic coefficient R² is close to 1 for the data model of the obtained second-order equation,and lack-of-fit tests of did not result in a significant F-value.According to the variance analysis,the fitting second-order polynomial model could evaluate the change of Mn leaching rate well.The influence degree of three factors on the response value is:sulfuric acid concentration>pyrite dosage>charcoal powder dosage.Based on manganese slag,the magnetic Manganese slag-carbon（MS-C）heterogeneous catalyst was obtained.Through single factor experiment,the optimal preparation conditions are as follows:The MS-C prepared by adding30.0 g manganese slag in the gel and the calcination temperature of 700℃shows the strongest catalytic activity.The data of X-ray diffraction（XRD）analysis shows that MS-C mainly contains Fe₃O₄,Mn Si O₃ and Si O₂.According to scanning electron microscope（SEM）results,it can be seen that the surface of MS-C is irregular and the irregular stacking mode leads to many voids.The vibrating sample magnetometry（VSM）test results shows that the saturation magnetic strength of MS-C is 17.3 emu·g^–1,which is lower than other magnetic composite materials,but it still can be separated from the solution rapidly in the external magnetic field.The catalytic degradation of Rhodamine B by MS-C was studied and the influence of various factors on the degradation effect was investigated through a single factor experiment.With the condition of MS-C dosage 2.0 g·L^–1,H₂O₂concentration 0.10 mol·L^–1,reaction temperature 30℃,the initial concentration of Rh B is 50 mg·L^-1,Rh B degradation rates reached up to 98%within 15 min and the degradation rate of Rh B conforms to the pseudo-first-order kinetic model.The study on the mechanism of degradation Rh B by MS-C revealed that·OH is plays an important role in the catalytic degradation of Rh B.The degradation rate of Rh B decreased by only 3%after MS-C was used for three cycles,which indicated that the MS-C has excellent reusability.The Ascorbic acid promoted MS-C degradation of Methylene blue was studied.Methylene blue degradation rates reached up to 74%within 30 min under the condition of MS-C dosage 1.0 g·L^–1,H₂O₂ concentration 0.05 mol·L^–1,0.5 m L AA solution（50 m M）and reaction temperature 30℃.The effect of HCO₃^-on the degradation rate of the system has two sides.It shows an inhibitory effect at low concentration and a promoting effect at high concentration.And the presence of Cl^-inhibited the degradation of Methylene blue.After repeated use of MS-C for three times,the degradation rate of Methylene blue decreased by 8%.The main reason is that AA can induce partial dissolution of Fe₃O₄ in MS-C,resulting in the reduction of active substances.