Enhanced Mn^(2+)solidification and NH_(4)^(+)-N removal from electrolytic manganese metal residue via surfactants

Electrolytic manganese metal residue(EMMR)harmless treatment has always lacked a low-cost and quick processing technology.In this study,surfactants,namely tetradecyl trimethylammonium chloride(TTC),sodium dodecyl benzene sulfonate(SDBS),sodium lignin sulfonate(SLS),and octadecyl trimethylammonium chloride(OTC),were used in the solidification of Mn^(2+)and removal of NH_(4)^(+)-N from EMMR.The Mn^(2+)and NH_(4)^(+)-N concentrations under different reaction conditions,Mn^(2+)solidification and NH_(4)^(+)-N removal mechanisms,and leaching behavior were studied.The results revealed that the surfactants could enhance the Mn^(2+)solidification and NH_(4)^(+)-N removal from EMMR,and the order of enhancement was as follows:TTC>SDBS>OTC>SLS.The NH_(4)^(+)-N and Mn^(2+)concentrations were 12.3 and 0.05 mg·L^(-1)with the use of 60.0 mg·kg^(-1)TTC under optimum conditions(solid–liquid ratio of 1.5:1,EMMR to BRM mass ratio of 100:8,temperature of 20℃,and reaction duration of 12 h),which met the integrated wastewater discharge standard(GB8978-1996).Mn^(2+)was mainly solidified as Mn(OH)_(2),MnOOH and MnSiO_(3),and NH_(4)^(+)-N in EMMR was mostly removed in the form of ammonia.The results of this study could provide a new idea for cost-effective EMMR harmless treatment.

Metallic Reserves of Submarine Manganese Nodules to be Estimated and Harnessed Prudently: Evidence from China's Jiaolong Manned Submersible

Since the discovery of oceanic manganese nodules during the expedition of the British ocean-going ship Challenger from 1872 to 1876, research and development for seabed manganese nodules have never ceased owing to the huge economic inducements. Manganese nodules are the black or dark brown, spherical or massive Mn-bearing ores, deposits of which are found on the sea bottom. The nodules are a mixture of silicate and insoluble potassium permanganates （also with sub-Ti, Fe and Na permanganates） that contain more than 30 kinds of metallic elements, among which those of greatest economic interest are Mn （27-30%）, Ni（1.25-1.5%）, Cu（1- 1.4%）, Co（0.2- 0.25 %）, Fe, Si, and AI, with minor amounts of Ca, Na, K, Ti, B, H and O.

Desulfurization of rejected electrolytic manganese metal by electroslag remelting furnace with a water-cooled electrode

Remelting rejected electrolytic manganese metal (EMM) scrap was investigated by electroslag remelting (ESR) process through industrial experiment. The results indicated that the ANF-6 slag (70 wt.% CaF_(2) + 30 wt.% Al_(2)O_(3)) and deoxidizer could promote the desulfurization of ESR manganese in an air atmosphere. Under an air atmosphere, the sulfur in the ingot decreased to 0.0534 wt.% with a desulfurization ratio of ESR manganese of 53.2% by using ANF-6 slag and water-cooled copper electrode electroslag remelting rejected EMM scrap, suggesting its efficient removal. The electroslag ingots exhibited uneven chemical composition in an air atmosphere and cooling condition of the ESR process. The metal manganese could be oxidized by electroslag remelting of rejected EMM scrap in an air atmosphere with MnO content in the final slag of 21.9 wt.%. Besides, the activity of MnO in slag increased with increasing remelting temperature, resulting in a reduction in the slag–manganese sulfur partition ratio and desulfurization ratio. Moreover, with the accumulation of sulfur in slag and the oxidation of metallic manganese liquid, the slag showed a lower cleanliness and more oxidation, leading to an increase in sulfur and oxygen content in the electroslag ingot with the increase in ingot height.

Effects of slag composition and additive type on desulfurization of rejected electrolytic manganese metal scrap by Na2O-containing electroslag

The recycling rate of rejected electrolytic manganese metal(EMM)scrap can be increased by inhibiting the manganese metal(MM)vaporization during the remelting process with electroslag.However,if the latter is achieved by reducing the remelting temperature,the desulfurization behavior will deteriorate.Therefore,Na_(2)O-containing electroslag and metallic additive were used to increase the rejected EMM scrap recovery ratio.The respective high-temperature experiment was conducted in a MoSi_(2) electrical resistance furnace filled with fluid argon at 1673 K using five different types of electroslag with the Na_(2)O content ranging from 5.81%to 15.71%.High-purity metallic magnesium and magnesium calcium alloy additives were used as deoxidizers.The addition of Na_(2)O and metallic additives effectively promoted the desulfurization and deoxidization of MM.The removal of sulfur and oxygen by the interaction between Na_(2)O-containing electroslag melt and molten MM with metallic additive was analyzed from the thermodynamic and kinetic standpoints.The effect of Na_(2)O-containing electroslag volatilization on desulfurization and deoxidization was considered.With an increase in Na_(2)O content in the slag,the mass loss rates of Na_(2)O and electroslag rose,as well as the final sulfur partition ratio.If the Na_(2)O content volatilized in the slag melt did not exceed 10.44%,the sulfur removal ratio was increased by high sulfide capacity and CaO activity in all slags due to the addition of Na_(2)O.The rejected EMM scrap deoxidization ratio grew with the increased activity of CaO and reduced activity of Al_(2)O_(3) in the molten slag,caused by the increased Na_(2)O content in the molten slag.The addition of metallic Mg and Mg-Ca alloy indirectly promoted desulfurization and deoxidization by reducing the MnO content in the rejected EMM scrap and growing slag oxidability.The Mg-Ca alloy could also react with dissolved sulfur and oxygen,directly promoting desulfurization and deoxidization processes.The Na_(2)O content in slag should not exceed 10.44%to ensure the high desulfurization and deoxidization abilities,fluidity and low volatilization of slag.

Near-unity quantum yield in zero-dimensional lead-free manganese-based halides for flexible X-ray imaging with high spatial resolution

Low-dimensional luminescent lead-free metal halides have received substantial attention due to their unique optoelectronic properties.Among them,zero-dimensional(0D)manganese(II)-based metal halides with negligible self-absorption have emerged as potential candidates in X-ray scintillators.Herein,we for the first time report a novel lead-free(TBA)_(2)MnBr_(4) single crystal synthesized via a facile solvent evaporation method.In this crystal,[MnBr_(4)]^(2-)units are isolated by large TBA^(+)organic cations,resulting in a unique 0D structure.The prepared manganese-based crystals exhibit a bright-green emission centered at 512 nm with a high photoluminescence quantum yield(PLQY)of 93.76%at room temperature,originating from the ^(4)T_(1)–^(6)A_(1) transition of Mn^(2+).Apart from their outstanding optical performance,the crystals also show excellent stability and can maintain 94.4%of the initial PLQY even after being stored in air for 90 days.Flexible(TBA)_(2)MnBr4 films prepared as X-ray imaging scintillators exhibit a low detection limit of 63.3 nGyair/s,a high light yield of 68000 ph/MeV,and a high spatial resolution of 15.4 lp/mm.Thus,this work not only enriches the family of lead-free metal halides but also expands the application of manganese(II)-based halides in flexible X-ray scintillators.

Removal of Pb(Ⅱ) from aqueous solution by hydrous manganese dioxide:Adsorption behavior and mechanism

Hydrous manganese dioxide （HMO） synthesized by redox of potassium permanganate and hydrogen peroxide was used as an adsorbent for Pb（Ⅱ） removal.The specific surface area,pore volume and BJH pore diameter of the HMO were 79.31m2/g,0.07cm3/g and 3.38 nm,respectively.The adsorption equilibrium at 298K could be well described by the Langmuir isotherm equation with q max value of 352.55mg/g.The negative values of G and the positive values of H and S indicated the adsorption process was spontaneous and endothermic.The pseudo second-order equation could best fit the adsorption data.The value of the calculated activation energy for Pb（Ⅱ） adsorption onto the HMO was 38.23 kJ/mol.The uptake of Pb（Ⅱ） by HMO was correlated with increasing surface hydroxyl group content and the main adsorbed speciation was PbOH＋.The final chemical state of Pb（Ⅱ） on the surface of HMO was similar to PbO.HMO was a promising candidate for Pb（Ⅱ） removal from aqueous solution.

Manufacturing of Long Products Made of Innovative Lightweight Materials

The processing of innovative lightweight materials to sheet metal components and assemblies with globally or locally defined properties is the object of this work. It takes a load-dependent design of components and assemblies, for example, based on the composition of different construction materials or a targeted setting of component areas with specified characteristics to fully exploit the lightweight potential when substituting conventionally used materials. Different process chains for the manufacturing of roll-formed long products made of magnesium alloys and high-strength steels with locally defined properties will be presented in this paper. Depending on the kind of material to be formed and the desired product characteristics, different temperature managements are needed for capable processes. Due to limited formability at room temperature, magnesium alloys require a heating of the forming zones above 200–225 °C throughout the bending process in order to activate additional gliding planes and to avoid any failures in the radii. The realization of local hardening effects requires at least one process-integrated heat treatment when roll forming manganese–boron steels. For both processes, it is imperative to realize a heating and cooling down or quenching appropriate for the manufacturing of long products with the required quality. Additionally, proper line speeds that allow a continuously operated economical production have to be considered. Research results including design, FEA, realization and experimentation of the mentioned process chains and strategies will be described in detail.