Preparation of manganese sulfate from low-grade manganese carbonate ores by sulfuric acid leaching

In this study, a method for preparing pure manganese sulfate from low-grade ores with a granule mean size of 0.47 mm by direct acid leaching was developed. The effects of the types of leaching agents, sulfitric acid concentration, reaction temperature, and agitation rate on the leaching efficiency of manganese were investigated. We observed that sulfuric acid used as a leaching agent provides a similar leach- ing efficiency of manganese and superior selectivity against calcium compared to hydrochloric acid. The optimal leaching conditions in sul- furic acid media were determined; under the optimal conditions, the leaching efficiencies of Mn and Ca were 92.42% and 9.61%, respec- tively. Moreover, the kinetics of manganese leaching indicated that the leaching follows the diffusion-controlled model with an apparent ac- tivation energy of 12.28 kJ·mol-l. The purification conditions of the leaching solution were also discussed. The results show that manganese dioxide is a suitable oxidant of ferrous ions and sodium dimethyldithiocarbamate is an effective precipitant of heavy metals. Finally, through chemical analysis and X-ray diffraction analysis, the obtained product was determined to contain 98% of MnSOa4·H20.

Rare earth elements(REE)and isotope composition(δ^(13)C andδ^(18)O)of manganese ores of Chiatura deposit(Georgia):features of ore formation and genesis

The rare earth elements(REE)geochemistry and the isotope(δ^(13)C,δ^(18)O)composition of manganese ores of the Chiatura(Georgia)deposit were studied.One of the major features of all types of manganese ores is negative cerium(Ce/Ce*_(PAAS))anomaly and the absence of europium(Eu/Eu*_(PAAS))anomaly.Oxide oolitic manganese ores were formed in oxic shallow marine environments.The content and distribution of REEs(in particular Ce and Eu)in these ores are connected mainly with ferrous oxides.The performed C-and O-isotope research in Mn-carbonates(oolitic and massive)has indicated that carbonate ores were formed by the participation of isotopic ally light CO_(2)which is a result of the oxidation of organic matter in the sediment strata by reducing environments of early diagenesis(and,partially,catagenesis)zone.Obtained negative cerium anomalies in the studied carbonate ores reflect the specific REE patterns in pore waters of sediments of earlier isdiagenesis zone of the Oligocene Chiatura's basin.The deficiency of cerium in this zone remains debatable and requires further study.Formation of manganese carbonates took place multistage by the input of incisional solutions of different chemistry into sea bottom waters and sediments.The absence of europium anomaly indicates about lack of hydrothermal solution input.

Behaviors of Lanthanum and Cerium on Grain Boundaries in Carbon Manganese Clean Steel

The behaviors of La and Ce on gram boundaries in carbon manganese clean steel were investigated by high-reso- lution transmission elecetron microscope （HRTEM）, scanning elecetron microscopy（SEM ）, energy dispersive spectrometer （EDS） and X-ray diffraction（XRD） analysis. The existing forms of rare earths （RE） in clean steel were as follows： dissolved in sohd solution, forming inclusion or second phase containing RE （RE-Fe-P, La-P, Fe-La eutectic and Fe-Ce phase）. The dissolved La or Ce segregated at grain boundaries. The segregation of both S and P at gram boundaries was reduced with suitable RE content. The impact toughness of the steel was improved obviously. La and Ce had effecets on purifying molten steel and modifying inclusions in clean steel, whereas with excessive La or Ce, La-Fe-P, La-P and Fe-La eutecetic phase or Ce-Fe-P and Fe-Ce intermetallic compound would form along grain boundaries, causing the impact energy to decrease significantly.

Tellurium-driven maple leaf-shaped manganese nanotherapeutics reshape tumor microenvironment via chemical transition in situ to achieve highly efficient radioimmunotherapy of triple negative breast cancer

The therapeutic efficacy of radioimmunotherapy against triple negative breast cancer(TNBC)is largely limited by the complicated tumor microenvironment(TME)and its immunosuppressive state.Thus developing a strategy to reshape TME is expected to achieve highly efficient radioimmunotherapy.Therefore,we designed and synthesized a tellurium(Te)-driven maple leaf manganese carbonate nanotherapeutics(MnCO3@Te)by gas diffusion method,but also provided a chemical catalytic strategy in situ to augment ROS level and activate immune cells for improving cancer radioimmunotherapy.As expected,with the help of H2O2 in TEM,MnCO3@Te heterostructure with reversible Mn3+/Mn2+transition could catalyze the intracellular ROS overproduction to amplify radiotherapy.In addition,by virtue of the ability to scavenge H+in TME by carbonate group,MnCO3@Te directly promote the maturation of dendritic cells and macrophage M1 repolarization by stimulator of interferon genes(STING)pathway activation,resulting in remodeling immuno-microenvironment.As a result,MnCO3@Te synergized with radiotherapy and immune checkpoint blockade therapy effectively inhibited the breast cancer growth and lung metastasis in vivo.Collectively,these findings indicate that MnCO3@Te as an agonist,successfully overcome radioresistance and awaken immune systems,showing promising potential for solid tumor radioimmunotherapy.

Effects of cooling rate and Al on MnS formation in medium-carbon non-quenched and tempered steels

The effect of Al on the morphology of MnS in medium-carbon non-quenched and tempered steel was investigated at three different cooling rates of 0.24, 0.43, and 200°C·s^-1. The formation mechanisms of three types of MnS were elucidated based on phase diagram information combined with crystal growth models. The morphology of MnS is governed by the precipitation mode and the growth conditions. A monotectic reaction and subsequent fast solidification lead to globular Type I MnS. Type II MnS inclusions with different morphological characteristics form as a result of a eutectic reaction followed by the growth in the Fe matrix. Type III MnS presents a divorced eutectic morphology. At the cooling rate of 0.24°C·s^-1, the precipitation of dispersed Type III MnS is significantly enhanced by the addition of 0.044wt% acid-soluble Al（Als）, while Type II MnS clusters prefer to form in steels with either 0.034wt% or 0.052wt% Als. At the relatively higher cooling rates of 200°C·s^-1 and 0.43°C·s^-1, the formation of Type I and Type II MnS inclusions is promoted, and the influence of Al is negligible. The results of this work are expected to be employed in practice to improve the mechanical properties of non-quenched and tempered steels.

Alkaline pretreatment for chlorine removal from high-chlorine rhodochrosite

Chloride in manganese ore adversely affects mineral extraction. The mechanisms and the factors that influence an alkali pretreatment to removal chlorine from manganese ore were explored to eliminate hazards posed by chlorine during the electrolysis of manganese. The results showed that sodium carbonate, when used as an alkaline additive, promoted the dissolution of insoluble chloride, enhanced the migration of chloride ions, and effectively stabilized Mn^（2＋）. The optimal conditions were a sodium carbonate concentration of 0.45 mol·L^（-1）, a liquid-solid ratio of 5：1 mL ·g^（-1）, a reaction time of 1 h, and a temperature of 25°C. The chlorine removal efficiency was greater than 95%, and the ore grade（Mn） was increased by 2.7%.

Carbon nanotubes as conducting support for potential Mn-oxide electrocatalysts： Influences of pre-treatment procedures

Different oxygen and nitrogen containing functional groups were created on the surface of the multiwalled carbon nanotubes. The multi-walled carbon nanotubes were treated in ultrasonic bath with sulfuric or nitric acid. Furthermore the surface texture was modified by increase of the roughness. In particular after treatment with the oxidizing nitric acid, in comparison to the H2SO4 or ultra-sonic treated samples,craters and edges are dominating the surface structures. Manganese oxide was deposited on the multiwalled carbon nanotubes by precipitation mechanism. Various manganese oxides are formed during the deposition process. The samples were characterized by elemental analysis, microscopy, thermal analysis,Raman spectroscopy, and by the zeta potential as well as X-ray diffraction measurements. It was shown that the deposited manganese oxides are stabilized rather by surface texture of the multi-walled carbon nanotubes than by created functional groups.

In-situ construction of MnCO_(3)@CNTs nanosheets for high-capacity aqueous zinc ion batteries

Owing to severe agglomeration of manganese carbonate(MnCO_(3))during its synthesis,it exhibits rapid decay cycle performance when used as a cathode material in aqueous zinc ion batteries.To overcome this drawback,we synthesized a MnCO_(3)material with carbon nanotubes(CNTs)(i.e.,MnCO_(3)@CNTs)via a one-step solvothermal method using a hybrid modification strategy.MnCO_(3)nanospheres were grown in-situ on a two-dimensional(2D)plane that was orderly interwoven by tubular single fibers of carbon to form a leaf-like nanosheet structure.The surface area of the MnCO_(3)@CNTs material was enlarged enormously through the special nanosheet structure,and its stability was improved by the supporting structure of the CNTs.As a result,the MnCO_(3)@CNTs exhibited a discharge capacity of 247.6 mAh g^(-1)at a current density of 0.1 A g^(-1).The energy storage mechanism of MnCO_(3)@CNTs was further explored using a series of electrochemical kinetic analyses and ex-situ characterization tests.This modification method not only broadens the application field of MnCO_(3),but also provides the possibility of modifying more cathode materials.

Evolution of Al2O3 inclusions by cerium treatment in low carbon high manganese steel

The influence of cerium（Ce）treatment on the morphologies,size and distributions of Al_2O_3 inclusions in low carbon high manganese steel was investigated by OM,SEM-EDS and theoretical calculation.The results showed that Ce can modify the morphologies and types of Al_2O_3 inclusions.After Ce treatment,the irregular Al_2O_3 inclusions were replaced by smaller and dispersive spherical cerium oxysulfides.The effects of treatment time and Ce content on the evolution of Al_2O_3 inclusions were examined.It indicated that Al_2O_3 inclusions were wrapped by rare earth inclusions to form a ring like shape Ce-enriched band around the inclusions.Model was established to elucidate the evolution mechanism of Al_2O_3 inclusions.Evolution kinetics of inclusions was discussed qualitatively to analyze the velocity controlled step.It was found that diffusion of Ce^（3＋）and Al^（3＋）in solid inclusion core and the formed intermediate layer would be the limited step during the evolution process.

Effect of austenization temperature on the microstructure evolution of the medium manganese steel (0.2C-5Mn) during ART-annealing

Microstructure evolution during ART-annealing （austenite reverted transformation annealing） of 0.2C-5Mn steel processed by austenitation at different temperatures was examined by SEM, TEM and XRD. It was demonstrated that the initial mi- crostructures resulted from austenization at different temperatures strongly affect the microstructure evolution during followed ART-annealing, even the ultrafine grained ferrite/austenite duplex structure with about 30% austenite could be obtained af- ter long time ART-annealing in all cases. Austenization in the intercritical region （between Ad and At3） gave a duplex structure after quenching, which was nearly not affected by followed annealing process. However, high temperature austenization （above A^3） resulted in a full martensite structure after quenching, which gradually transformed into a ferrite/austenite duplex structure during the following anneal- ing process. Based on the analysis of austenite fraction and carbon concentrate, it was found that not only carbon partitioning but also manganese paxtitioning in the austenite affected the stability of austenite and even dominated the development of lamellar ferrite and austenite duplex structure during intercritical annealing with different times. At last an austenite lath nucleation and thickening model was pro- posed to describe the microstructure evolution of medium mangenese steel during ART-annealing.

Synthesis of MnxOy@C hybrid composites for optimal electromagnetic wave absorption capacity and wideband absorption

The fabrication of high-performance electromagnetic(EM)wave absorption(EMA)materials is an effective strategy to deal with ever-increasing EM pollution.In this work,a series of manganese oxides/porous carbon(Mn_(x)O_(y)@C)hybrid composites are obtained by a two-step process.It is revealed that different manganese oxides play various influence on the dielectric properties of absorbers.Owing to the moderate complex permittivity of MnO@C hybrid composites,the optimal reflection loss could reach as high as-76.0 dB at the matching thickness of 2.0 mm with 5.2 GHz of effective absorption bandwidth at thickness of 2.1 mm.We demonstrated that the addition of porous carbon is vital for enhancing EMA performance of composites,which not only coordinates impedance matching allowing more EM waves enter the absorber,but also provides the path for electron movement,thus profiting conductive loss.Besides,different heterogeneous interfaces including porous carbon,manganese oxide and so on,are conducive to contribution of interface polarization.The most noteworthy is ingenious design of composite materials and systematic research of EM energy attenuation mechanism in this work will provide the possibility to realize high-performance EMA.

Enhanced performance triboelectric nanogenerator based on porous structure C/MnO_(2)nanocomposite for energy harvesting

Triboelectric nanogenerator(TENG)can realize a variety of mechanical energy collections in the environment,which has great potential in the field of wearable energy.However,many TENGs could rarely be satisfactory to wearable electronics promotion because of their expensive raw materials and complex manufacturing processes.In this study,a type of porous structure carbon powder/manganese dioxide(C/MnO_(2))nanocomposite is introduced.The material adopts low-cost,high-yield carbon powder,can be prepared in one step through a simple,economical,and environmentally friendly hydrothermal preparation process,and has high economic practicality.Superior power generation performance was obtained by modulating the charge trapping ability and storage capacity of polydimethylsiloxane@C/MnO_(2)(PDMS@C/MnO_(2))film based on variations in the weight-loading of C/MnO_(2).The maximum output voltage of carbon powder/manganese dioxide TENG(CM-TENG)is 63 V,which is 2.1 times that of PDMS-TENG and 1.86 times that of carbon powder TENG(C-TENG)and can easily light up 53 LEDs.Furthermore,CM-TENG can convert biological motion energy into electrical signals to detect human hand movements.The CM-TENG self-powered system can successfully drive various microelectronic devices,such as electronic watches,liquid crystal displays(LCDs),and calculators.This study provides a reliable,low-cost,high-performance,and widely applicable electronic system that shows great potential in future fields such as wearable devices and micro-sensing systems.