Granulometry,cluster analysis and spatial distribution of manganese contaminated soils,Kgwakgwe, southeastern Botswana

The particle size distribution (PSD) of 400 Mn contaminated soil samples was established, and generated data were statistically analysed and spatially presented. The PSD for the 53 µm – 4 µm size fraction soil samples ranged from 11.05 to 100 wt %, whereas that for < 4 µm was from 0.3 to 30 wt %. Texturally, samples were dominantly silt loam, although silt and sandy loam were also present, as well as loam, loamy sand and clay classes. Six clusters were identified with cluster one being the most dominant occurring in sandy loam, silt loam and loamy sand. The < 53 µm fraction had three dominant areas, and the < 4 µm fraction had several unevenly presented populations as reflected in the maps. Because of its spatial distribution, the < 4 µm fraction may pose hazards to human health. Furthermore, predominance of Mn limits land use to subsistence agriculture with possibly low crop yield.     

Experimental investigations of the structural transformations induced by the heat treatment in manganese ferrite synthesized by ultrasonic assisted co-precipitation method

Manganese ferrite powder has been synthesized by ultrasonically assisted co-precipitation method using Fe(NO₃)₃·2H₂O and Mn(NO₃)₂·H₂O as precursors. The precipitate was washed and dried in oven at 80 °C for 2 h to obtain the initial MnFe₂O₄ powder (denoted by sample S1). Subsequently, other three samples (denoted by S2, S3 and S4) were prepared starting from the initial powder, which was subjected to heat treatment (for 2 h in air) at 400 °C (for sample S2), 700 °C (for sample S3) and 1000 °C (for sample S4). The structural and morphological analysis of samples has been studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). From the XRD analysis of samples one finds that the samples S1 and S2 consist of MnFe₂O₄ with cubic spinel structure, whilst the samples S3 and S4 consist of FeMnO₃ with perovskite structure and Fe₂O₃; meaning that the thermal treatment of MnFe₂O₄ induces chemical and structural transformation. The complex impedance measurements, over the frequency range 20 Hz–2 MHz and magnetic measurements have confirmed the structural transformation in the samples subjected of heat treatment.     

Fenton技术中残余组分对COD测定的干扰和消除研究

Fenton试剂与水样中难降解有机物反应后,残余组分会对后续水样COD测定产生干扰。实验表明,Fenton试剂残余组分中H_2O_2对COD测定产生的干扰较大,其对水样COD测定产生的影响值与H_2O_2浓度成良好的线性关系,而残余组分Fe~(2+)对COD测定产生的干扰与H_2O_2相比,影响值较小,可忽略其影响。通过对比分析掩蔽剂法、催化分解法对H_2O_2干扰消除试验得出,掩蔽剂Na_2SO_3能够迅速的与H_2O_2发生反应,消除H_2O_2的干扰,但掩蔽剂Na_2SO_3也会对水样COD产生一定的干扰,测量结果偏差较大;MnO_2催化分解H_2O_2的效率较高,很好的消除H_2O_2的干扰,但MnO_2分解后水样COD测定值需乘以折减系数0.89,满足试验精度的要求;过氧化氢酶可以将H_2O_2完全分解,分解效率较高,干扰消除效果较好。     

多金属结核矿浆电解的浸出机理研究

围绕多金属结核的矿浆电解,对多金属结核矿和MnO2在矿浆电解过程中锰的行为规律进行了研究。通过对不同条件下石墨阴极极化曲线的测定和纯二氧化锰矿浆电解浸出行为的研究,查明了多金属结核矿浆电解的阴极浸出反应机理。浸出过程中,阴极上发生的主要是FeCl(3-n)n的还原反应,多金属结核的浸出主要由FeCl(2-n)n,FeCl(3-n)nn来完成。阴极生成的FeCl(2-n)n被结核氧化成FeCl(3-n)又在阴极被还原为FeCl(2-n)n,如此反复。多金属结核的浸出可通过三种途径实现:阴极还原、化学还原和化学溶解,其中多金属结核与阴极碰撞发生的阴极还原反应对锰浸出的贡献率小于5%,多金属结核的浸出主要由FeCl(2-n)n完成。     

浅谈云南高炉锰铁的开发

分析了云南锰矿资源优势及焦炭资源状况，根据云南锰矿石特点与冶炼加工的关系，讨论了高炉锰铁生产的特点及优点，由此表明，在云南开发高炉锰铁比生产电炉锰铁具有更好的经济效益。     

用液膜技术分离模拟海洋锰结核浸出液中的钴和镍

本文研究了采用以EHPNA(P507)为流动载体的Span—80表面活性刺膜分离Co(Ⅰ)、Ni(Ⅰ)的最好效果,其分离系数βCo╱N_1=133,并且讨论了该液膜分离Co(Ⅰ)、Ni(Ⅰ)的条件以及从模拟海洋锰结核漫取液中提取Co(Ⅰ),Ni(Ⅰ)的效果。     

H2O2—水杨基荧光酮指示反应体系动力学光度法测定痕量锰

在碱性介质中，痕量锰（Ⅱ）能显著催化H2O2氧化水杨基荧光酮的反应。本文据此建立了测定痕量锰的催化动力学分析法，测定条件为：4．0×10－5mol／L水杨基荧光配（SAF）0．012／H2O2，2．4×10-2mol／LNaOH，60℃。线性范围为0．1～2．0μg／L，方法检测限为0.02μg／L。测得反应表现活化能为20．78kJ／mol。测定了土壤、碳素钢及铝合金等样品中锰的含量，结果满意。     

锌试剂褪色光度法测定茶水中锰含量

锌试剂是一种测定锌的常用显色剂。将锌试剂用于锰的测定未见报道。本文研究了锌试剂褪色光度法测定茶水中锰含量的方法。结果表明:在一定条件下,锰含量在2.7～32.0μg/L范围内遵守比耳定律,检测限为0.14μg/L,方法的表观摩尔吸光系数为8.2780×10~5L/mol·cm。经用于茶水样品分析,精密度(RSD)为2.0%～6.5%,回收率为90%～102%。结果令人满意。     

Hierarchical manganese sillenite Bi12MnO20 microparticles assembled by nanocubes with microwave absorption enhancement

Pure manganese sillenite (Bi₁₂MnO₂₀) microparticles with average sizes of 11.5–16.8 μm were prepared via an oxidation-precipitation method assisted by microwave-heating. Their microstructures are characterized by the shapes of single or multiple intersecting tetrahedrons and the massive nanocubes in ordered arrays on each tetrahedron surface. Such hierarchical Bi₁₂MnO₂₀ microparticles have not been reported so far, while their growth mechanisms may include the formation of active centers, the selective nucleation on active center surfaces and the growth of nanocubes along certain orientations. In electromagnetic determination, noticeable resonances both in permittivity and permeability were revealed beyond relaxations. A cone-like reflection loss peak was obtained with the minimum value of −39.1 dB and a broad effective microwave absorption bandwidth covering 12.7–14.6 GHz. Moreover, the reflection loss peak stagnates at the same frequency regardless of the absorbent thickness variations, suggesting a high performance in microwave attenuation.     

Sulfur resource recovery based on electrolytic manganese residue calcination and manganese oxide ore desulfurization for the clean production of electrolytic manganese

An environmentally friendly and resource-conserving route to the clean production of electrolytic manganese was developed, in which the electrolytic manganese residue(EMR) was initially calcined for cement buffering;then the generated SO_2-containing flue gas was managed using manganese oxide ore and anolyte(MOOA) desulfurization; at last, the desulfurized slurry was introduced to the electrolytic manganese production(EMP). Results showed that 4.0 wt% coke addition reduced the sulfur of calcined EMR to 0.9%, thereby satisfying the cement-buffer requirement. Pilot-scale desulfurization showed that about 7.5 vol% of high SO_2 containing flue gas can be cleaned to less than 0.1 vol% through a five-stage countercurrent MOOA desulfurization. The desulfurized slurry had 42.44 g·L~(-) Mn~(2+) and 1.92 g·L~(-1) S_2 O_6~(2-), which was suitable for electrowinning after purification, and the purity of manganese product was 99.93%, satisfy the National Standard of China YB/T051-2015.This new integrated technology fulfilled 99.7% of sulfur reutilization from the EMR and 94.1% was effectively used to the EMP. The MOOA desulfurization linked the EMP a closed cycle without any pollutant discharge, which promoted the cleaner production of EMP industry.