Effects of current density on preparation of grainy electrolytic manganese dioxide

Grainy electrolytic manganese dioxide was prepared by electrodeposition in a 0.9 mol/L MnSO4 and 2.5 mol/LH2SO4 solution. The structure, particle size and appearance of the grainy electrolytic manganese dioxide were determined by powder X-ray diffraction, laser particle size analysis and scanning electron micrographs measurements. Current density has important effects on cell voltage, anodic current efficiency and particle size of the grainy electrolytic manganese dioxide, and the optimum current density is 30 A/dm2. The grainy electrolytic manganese dioxide electrodeposited under the optimum conditions consists of γ-MnO2 with an orthorhombic lattice structure; the grainy electrolytic manganese dioxide has a spherical or sphere-like appearance and a narrow particle size distribution with an average particle diameter of 7.237 μm.

Effects of temperature and concentration of sulfuric acid on the electrodeposition of grainy electrolytic manganese dioxide

The effects of temperature and the concentration of sulfuric acid on the cell voltage, the anode current efficiency of electrodeposition and the particle size of grainy electrolytic manganese dioxide （EMD） were investigated. The structure, particle size and appearance of grainy EMD were determined by powder X-ray diffraction, laser particle size analysis and scanning electron micrograph measurements. As the concentration of sulfuric acid increases, both the cell voltage and the average anode current efficiency decrease. With the increase of electrolysis temperature in the range of 30-60℃, the cell voltage, average anode current efficiency and particle size decrease. The optimum temperature of 30℃ and concentration of sulfuric acid of 2.5 mol/L for electrodeposition of the grainy EMD were obtained. XRD patterns show that the grainy EMD electrodeposited under the optimum conditions consists of γ-MnO2 and has an orthorhombic lattice structure. According to the results of SEM, the grainy EMD has a spherical or sphere-like appearance and a narrow particle size distribution with an average size of about 7μm. The grainy EMD is a promising cathode of rechargeable alkaline batteries for high energy density and a prospective precursor for production of the LiMn2O4 cathode of lithium ion batteries.

Flexible Zinc-Manganese Dioxide Alkaline Batteries Based on Kelp Electrolytes

Flexible energy-storage devices play a critical role in the development of portable, flexible and wearable electronics. In addition, biological materials including plants or plant-based materials are known for their safety, biodegradability, biocompatibility, environmental benignancy, and low cost. With respect to these advances, a flexible alkaline zinc-manganese dioxide (Zn-MnO2) battery is fabricated with a kelp-based electrolyte in this study. To the best of our knowledge, pure kelp is utilized as a semi-solid electrolyte for flexible Zn-MnO2 alkaline batteries for the first time, with which the as-assembled battery exhibited a specific capacity of 60 mA·h and could discharge for 120 h. Furthermore, the as-assembled Zn-MnO2 battery can be bent into a ring-shape and power a light-emitting diode screen, showing promising potential for the practical application in the future flexible, portable and biodegradable electronic devices.

Preparation of MnO_2 and calcium silicate hydrate from electrolytic manganese residue and evaluation of adsorption properties

Electrolytic manganese residue(EMR), a high volume byproduct resulting from the electrolytic manganese industry, was used as a cheap and abundant chemical source for preparing MnO2 and EMR-made calcium silicate hydrate(EMR-CSH). The MnO2 is successfully synthesized from the metal cations extracted from EMR, which can effectively recycle the manganese in the EMR. By the combination of XRD, SEM and EDX analysis, the as-prepared MnO2 is found to exhibit a single-phase with the purity of 90.3%. Furthermore, EMR-CSH is synthesized from EMR via hydrothermal method. Based on the detailed analyses using XRD, FT-IR, FE-SEM, EDX and BET surface area measurement, the product synthesized under the optimum conditions(p H 12.0 and 100 °C) is identified to be a calcium silicate hydrate with a specific surface area of 205 m2/g incorporating the slag-derived metals(Al and Mg) in its structure. The as-synthesized material shows good adsorption properties for removal of Mn2+ and phosphate ions diluted in water, making it a promising candidate for efficient bulk wastewater treatment. This conversion process, which enables us to fabricate two different kinds of valuable materials from EMR at low cost and through convenient preparation steps, is surely beneficial from the viewpoint of the chemical and economical use of EMR.

Reductive recovery of manganese from low-grade manganese dioxide ore using toxic nitrocellulose acid wastewater as reductant

The hydrometallurgical strategy of extracting Mn from low-grade Mn ores has attracted attention for the production of electrolytic manganese metal(EMM). In this work, the reductive dissolution of low-grade Mn O2 ores using toxic nitrocellulose acidic wastewater(NAW) as a reductant was investigated for the first time. Under the optimized conditions of an Mn O2 ore dosage of 100 g·L-1, an ore particle size of-200 mesh, concentrated H2 SO4-to-NAW volume ratio of 0.12, reaction temperature of 90°C, stirring speed at 160 r·min-1, and a contact time of 120 min, the reductive leaching efficiency of Mn and the total organic carbon(TOC) removal efficiency of NAW reached 97.4% and 98.5%, respectively. The residual TOC of 31.6 mg·L-1 did not adversely affect the preparation of EMM. The current process offers a feasible route for the concurrent realization of the reductive leaching of Mn and the treatment of toxic wastewater via a simple one-step process.

单膜双室电沉积金属锰联产EMD的影响因素

针对传统膜电解法单独电解金属锰或电解二氧化锰(EMD)工艺存在资源利用率低、污染环境的问题,采用单膜双室电解法将金属锰与EMD进行同槽电解,且在阳极回收硫酸,并考察了阴极液硫酸铵浓度、电解液Mn^(2+)浓度、阳极液初始硫酸浓度、电流密度4个因素对电沉积效果的影响。结果表明:在阴极液硫酸铵浓度为120 g/L、电解液Mn^(2+)浓度为40 g/L、阳极液初始硫酸浓度为0.6 mol/L、阴阳两极的电流密度分别为400 A/m^(2)和800 A/m^(2)的条件下,进行6 h电解,得到阴极锰产率可达78.22%,酸回收率为62.41%,EMD产率为23.7%,电能消耗仅为5675 kW·h/t,槽电压为5.86 V。同时发现对锰产率影响最显著的因素是电流密度,对EMD产率及酸回收率影响最显著的因素是阳极液初始硫酸浓度和电流密度。在最佳实验条件下的阴极产品金属锰板表面光洁密实、具明显银白色金属光泽、晶粒分层聚集、颗粒粒度均一、并呈现蜂窝状组织,整体形态良好。

电解二氧化锰(EMD)粉体流动性试验研究

以EMD粉体为研究对象,借助HORIBA粒度分布测试仪、BT-1001粉体流动性能测试仪,进行粉体流动性表征评价。通过表征得到粉体物性参数与流动性参数之间的函数关系,发现粉体物性对压缩性、流动性的影响规律不同,构建了不同流动性参数间的关联式,获得了休止角、流动性指数和喷流性指数的线性关系式,以期为EMD流动性和产品加工性能提供一种表征评价手段,对生产实践具有一定的指导作用。

电解二氧化锰(EMD)铜阴极结晶发黑的机理分析和改善方法

电解二氧化锰(EDM)广泛应用于一次电池和二次电池,作为二次电池固相法工艺的锰源,EMD不仅对纯度与杂质有要求,同时还对颗粒形状、比表面积等有要求,整体工艺技术门槛较高,生产中出现的问题也较多。研究发现在EMD生产过程中,铜阴极易结晶发黑,结合EMD的电解生产工艺,分析铜阴极结晶发黑的原因,提出并实施相应的处理措施,改善铜阴极结晶发黑的现象。

锰氧化物正极材料的低温焙烧制备及电化学性能

以电解锰阳极泥(EMAM)为原料,利用焙烧活化法制备了水系锌离子电池(AZIBs)锰氧化物正极材料,通过XRD、TGA、SEM及电化学性能测试考察了氮气氛围下,不同焙烧温度(300、425、575℃)对锰氧化物正极材料的结构、形貌及电化学性能的影响。结果表明,氮气氛围下焙烧提高了锰氧化物正极材料的衍射峰强度和结晶度,材料呈现出片状和颗粒状形态,团聚现象减少,空隙增加;随着焙烧温度的提高,锰氧化物正极材料物相逐渐从α-MnO_(2)转变为Mn_(2)O_(3)与Mn_(3)O_(4);焙烧使锰氧化物正极材料的首次放电比容量、倍率性能和循环性能得到提升,材料具有较小的瓦尔堡系数和更快的Zn^(2+)扩散速度。其中,焙烧温度300℃制备的锰氧化物正极材料(300-EMAM)表现出更好的电化学性能,在5 C倍率下,300-EMAM的初始放电比容量为232 mA·h/g,循环100圈后仍能保持190 mA·h/g的放电比容量;300-EMAM电极具有较低的接触电阻(33.6Ω)和电荷转移电阻(816.3Ω)。

基于响应面法优化同槽电积锰和二氧化锰工艺研究

针对目前生产锰和电解二氧化锰行业能耗大、污染严重的问题,设计了一种同槽电沉积锰和二氧化锰工艺,在提高阴阳极电流效率的同时使得能耗最低,达到节能降耗的目的。结合响应面法对阴极硫酸铵浓度、阳极硫酸浓度、中隔室硫酸浓度、温度四个因素与阴阳极电沉积效率之间的交互作用进行分析,得到二次回归拟合模型,确定同槽电积的最佳条件为:阴极硫酸铵浓度为107.11 g/L,阳极硫酸浓度投加量为2.8 mol/L,中隔室硫酸浓度为0.516%,温度为40.2℃。阴极电流效率可达到84.79%、阳极电流效率可达到68.43%。分析表明,硫酸铵和温度对阴极电流效率交互影响最大、硫酸浓度和温度对阳极电流效率交互影响最大。电沉积得到的金属锰沉积紧密。电解二氧化锰粒径均一,形貌良好。

EMD与KOH溶液的相互影响

利用滴定分析、热失重分析以及XRD方法研究了EMD和KOH溶液混合后的变化。结果表明:碱与MnO2可以相互作用并导致体系温度的升高,碱浓度的下降,EMD中形成Mn3O4以及MnO2中结合水的损失。相互作用的结果与所加KOH溶液的浓度、EMD中的水含量、二者用量的比例关系以及体系的温度有关。

EMD生产中钛基钛锰合金阳极的电流效率

本文运用正交设计法探讨了电解二氧化锰生产中温度、酸度、电流密度对钛基钍锰合金阳极电流效率的影响,在保证EMD质量前提下,提出适应于新型阳极的最佳工艺参数。

EMD的离子交换行为及其离子筛法提取锂的研究

采用碳电极，在９０～９５℃范围内电解氯化锰溶液，制得纤维态电解二氧化锰，该样品对于氯化物溶液中的单种或混合阳离子具有交换性质。研究结果表明，以该样品为基体所制得的锂型离子筛，可用于从海水中提取微量锂，９０％的锂被选择交换。

FEMD的离子交换行为及其离子筛法提取锂的研究

采用碳电极,在90～95℃范围内,电解氯化锰溶液,制得纤维态电解二氧化锰(简称FEMD)。它是具有纤维态的Y-MnO_2,对于氯化物中的单种或混合阳离子具有交换性质。研究结果表明,以FEMD为基体所制得的锂型离子筛,可用于从海水中提取微量锂,有90％的锂被选择交换。

电池用EMD中不同晶型二氧化锰的定量相分析

用X射线衍射定量物相分析法.测定了不同产地EMD(电解二氧化锰)中不同晶型二氧化锰的含量.结果表明:日本和我国倾生产的EMD中,γ-MnO_2的含量较高,我国广西下田的较低,γ/β两种晶型含量比分别为84:6(日本),82:8(湘潭)和54:36(下田).本实验方法简捷、迅速、可靠,适合在电池工业生产中应用.

FEMD吸附水蒸汽的研究

采用静态吸附重量法研究了几种电解二氧化锰样品对水蒸汽的吸附,实验结果表明,样品经393.2K和523.2K处理2小时后,吸附水蒸汽的等温线外形类似于Ⅲ类吸附等温线。经523.2K处理2小时的样品,吸湿性低于经393.2K处理的样品。FEMD样品在常温下吸附后,并在低于50℃的温度下脱附2小时,反复进行10次,最后一次的吸附量相当于第一次吸附量的65％。

无汞碱锰电池用EMD中砷、锑的测定

用氢化物发生 原子荧光光谱法测定了无汞碱锰电池用电解二氧化锰中砷和锑,对仪器条件、试剂用量等进行了研究。方法的检出限:砷0 062μg/L,锑0 058μg/L;精密度:砷1 6%,锑1 0%;回收率:砷90%～104%,锑92%～102%。

采用TAB快速测定EMD性能

TAB(聚四氟乙烯乙炔黑)是好的导电和粘结合二为一的材料,采用该材料能快速评定EMD的性能。

微粒EMD电化学活性及应用

本文从等酸点pH值、pH—MnO_2电极电位,干电池放电容量等对微粒EMD同其他MnO_2进行比较,肯定了微粒EMD的电化学活性及应用价值。

Pb-Ag-Ca新型合金阳极(PAC阳极)用于电解MnO_2(EMD)的研究(Ⅲ)

根据由PAC阳极电解所得EMD及MnSO_4-H_2SO_4电解液中微量铅的微分脉冲极谱测定数据、所设计实验验证结果及理论分析,可确定EMD中微量铅的价态主要为PbO_2,含铅量为0.19％。用此EMD及配有PbO_2的EMD作成电池,其放电性能:连放时间为590min(负载为5Ω,终止电压为0.9v),开路电压为1.8v。此EMD达到一级品要求。PbO_2含量对电池放电性能无影响。