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JM Fell AP Reynolds N Meadows K Khan SG Long G Quaghebeur WJ Taylor PJ Milla 《Canadian Metallurgical Quarterly》1996,347(9010):1218-1221
BACKGROUND: In patients receiving long-term parenteral nutrition (PN), cholestatic disease and nervous system disorders have been associated with high blood concentrations of manganese. In such patients, the normal homoeostatic mechanisms of the liver and gut are bypassed and the requirement for this trace element is not known; nor has it been certain whether hypermanganesaemia causes the cholestasis or vice versa. We explored the direction of effect by serial tests of liver function after withdrawal of manganese supplements from children receiving long-term PN. We also examined the relation between blood manganese concentrations and brain lesions, as indicated by clinical examination and magnetic resonance imaging (MRI). METHODS: From a combined group of 57 children receiving PN we identified 11 with the combination of hypermanganesaemia and cholestasis; one also had a movement disorder. Manganese supplements were reduced in the first three and withdrawn in the remainder. MRI was done in two of these children. We also looked at manganese concentrations and MRI scans in six children who had received PN for more than 2 years without developing liver disease. FINDINGS: In the hypermanganesaemia/cholestasis group, four of the 11 patients died. In the seven survivors baseline whole-blood manganese was 615-1840 nmol/L, and after 4 months it had declined by a median of 643 nmol/L (p < 0.01). Over the same interval total bilirubin declined by a median of 70 mumol/L (p < 0.05). Two of these children had movement disorders, one of whom survived to have an MRI scan; this showed, with T1 weighted images, bilateral symmetrically increased signal intensity in the globus pallidus and subthalamic nuclei. Such changes were also seen in five other children--one from the hypermanganesaemia/cholestasis group and four of six in the long-term PN group without liver disease (in all of whom blood manganese was above normal). INTERPRETATION: The cholestasis complicating PN is multifactorial, but these results add to the evidence that manganese contributes. In view of the additional hazard of basal ganglia damage from high manganese levels in children receiving long-term PN, we recommend a low dose regimen of not more than 0.018 mumol/kg per 24 h together with regular examination of the nervous system. 相似文献
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Exposure to elevated levels of Manganese (Mn) can result in an irreversible brain disease characterized by extrapyramidal signs and symptoms resembling Parkinson's disease. To identify the neuronal target of Mn neurotoxicity, MnCl2 was added to serumless dissociated mesencephalic-striatal cultures from rat embryo on day 4 in vitro. High affinity 3H-dopamine (DA) and 14C-GABA uptakes were assessed as specific functional markers of DAergic and GABAergic cell viability, respectively. After 60-min exposure, MnCl2 at 0-200 microM did not modify the morphologic appearance of the cultures, specific DA and GABA uptakes, or the number of DA neurons visualized by immuno-cytochemical staining with tyrosine hydroxylase. In contrast, culture exposure to 20 microM MnCl2 for 24 h selectively reduced specific GABA uptake without affecting specific DA uptake or the number of DA neurons. The exposure to a higher MnCl2 concentration was accompanied by signs of general toxicity. Striatal GABA neurons seemed to be more susceptible to Mn toxicity than mesencephalic GABA neurons. Overall, our data suggest that striatal neurons rather than mesencephalic DA neurons may be the main target of Mn neurotoxicity. 相似文献
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对氧化锰矿与碳酸锰矿浸出相结合的分段浸出工艺进行研究。考察硫酸浓度、葡萄糖用量、反应温度、时间和液固比等对两段锰浸出率及浸出液余酸的影响。结果表明,在还原浸出氧化锰矿阶段,采用葡萄糖占氧化锰矿的质量比6.33%、硫酸浓度4.37 mol/L、液固比1.5、90℃反应3h,锰浸出率为93.7%;在第二浸出阶段,加入剩余阳极液及1.5倍氧化锰矿质量的碳酸锰矿,在液固比6、90℃继续反应3h时,总锰浸出率达96.1%,浸出液余酸值降为9.4g/L。 相似文献
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Conclusions An investigation was carried out into the kinetics of the process of formation of manganese nitrides in nitrogen and ammonia streams. It was established that the rate of formation of manganese nitrides is higher in ammonia than in nitrogen. The kinetic parameters of manganese nitride formation were calculated.It is shown that in nitrogen the only manganese nitride that can be synthesized in the pure form is MnN. In ammonia, depending on the temperature and duration of the nitriding process, it is possible to obtain MnN, Mn2N, and Mn3N2 in the pure form, free from any other phases.A study was made of the chemical stability of manganese nitrides of compositions Mn4N and Mn3N2 in water and in concentrated and dilute mineral acids. It was established that these two nitrides are stable in water. In mineral acids they dissolve, the rate of dissolution being higher in concentrated than in dilute acids. In nitric acid Mn4N and Mn3N2 decompose with the liberation of part of the nitrogen in molecular form.Translated from Poroshkovaya Metallurgiya, No. 3(171), pp. 65–70, March, 1977. 相似文献
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锰矿石中锰的物相分析是基于各种形式的锰在某种溶剂中溶解度不同这一性质来逐个分离,然后分别进行测定的一类特殊分析方法;锰矿石中锰的物相分析是深入研究有用矿物组成的重要手段。 相似文献
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针对两矿法浸出高铁氧化锰矿存在生成大量单质硫并覆盖在矿物颗粒表面,降低了反应速率的问题,研究采用在浸出过程中添加木炭粉的方法吸附单质硫以改善浸出效果。考察了木炭粉添加量、硫铁矿用量、硫酸浓度、浸出温度和浸出时间对高铁氧化锰矿中锰浸出率的影响。在高铁氧化锰矿用量10.0g、硫铁矿用量5.0g、木炭粉添加量0.1g、硫酸浓度1.36mol/L、浸出温度70℃和浸出时间4h的条件下,锰浸出率达到96.7%。 相似文献
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高硫碳酸锰矿与软锰矿直接浸出实验 总被引:1,自引:0,他引:1
传统电解锰生产中,软锰矿需要经过还原焙烧将其中的Mn4+还原为Mn2+才能被稀硫酸浸出制得MnSO4溶液。利用高硫碳酸锰矿中的硫铁矿成份和浸出时产生的具有还原性的H2S和溶液中的Fe2+,可以直接浸出软锰矿中的Mn4+。经过多次实验对比,总结出了较理想的高硫碳酸锰矿与软锰矿的配矿比,既有利于高硫碳酸锰矿在浸出时产生的H2S的利用吸收,减少尾气中的H2S,给尾气处理减轻负担,又有利于保持较高的浸出率,可为高硫碳酸锰矿和软锰矿的直接浸出提供参考。 相似文献
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广西大新锰矿碳酸锰矿产资源的开发利用 总被引:1,自引:0,他引:1
通过分析广西大新锰矿当前矿山生产经营情况和氧化锰矿保有地质储量逐年减少的趋势,以及对碳酸锰矿地质条件及其矿石可选性试验研究的探讨,论述了开发利用碳酸锰矿的可行性和必要性。 相似文献
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研究了采用一种新型萃取剂A从电解锰阳极液中通过溶剂萃取获得制备电池级硫酸锰的高纯溶液,考察了振荡时间、水相pH、萃取剂浓度、有机相皂化率、相比Vo/Va、硫酸铵浓度对萃取的影响,以及相比Vo/Va和酸度对反萃取的影响.结果表明:在Vo/Va=1.5/1、萃取剂体积分数30%、有机相皂化率30%、水相pH=4.6、25℃条件下萃取15 min,锰萃取率为77.9%,镁萃取率为13.7%;用1 mol/L硫酸溶液,在相比V o/V a=6/1条件下反萃取负载有机相,得到平均锰质量浓度53 g/L、酸度较低的反萃取液;用此反萃取液制得的硫酸锰产品中锰质量分数大于32%,镁质量分数低于1.5×10-5,符合化工行业《电池用硫酸锰》一等品要求. 相似文献
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利用二氧化锰矿粉和硫酸的氧化作用浸出锰金属,再通过调节浸出液pH除大部分的铁,然后在不同pH条件下采用P204萃取剂两步法除钙铁和回收锰,最后经硫酸反萃取后浓缩结晶制备高纯硫酸锰。最佳工艺条件为:在硫酸浓度100g/L、液固体积质量比6mL/g、渣料质量比8、浸出温度90℃、浸出时间180min,锰浸出率可达93.5%;调节浸出液pH=4.0除大部分的铁,除铁率达到了84.8%,溶液浓缩定容至20mL,调节浸出液pH=1.6,加入体积比1∶1、皂化率30%的P204和磺化煤油萃取剂,萃取10min,钙、铁萃取率分别达到了91.2%和80.5%,再次调节浸出液至pH=3.5,加入体积比2∶1、皂化率30%的P204和磺化煤油萃取剂,萃取10min,锰萃取率最高达92.9%,最后经硫酸反萃取后浓缩结晶制备高纯硫酸锰,锰的总回收率达到了82.6%,溶液经浓缩结晶后得到的高纯硫酸锰纯度达到了99.78%,含铁0.0012%、钙0.0023%。 相似文献
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简要概述了国内锰矿资源的分布和特点,从矿产资源量、品位和经济效益3个方面分析了国内锰矿不能满足电解金属锰生产的现状,并指出了进口锰矿在电解金属锰生产应用中的优势与前景。 相似文献
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研究一步法还原浸出低品位氧化锰矿制备硫酸锰工艺。使用亚硫酸盐作为还原剂,采用黄铁矾法除铁,硫化盐法去除重金属离子,最终制备出适用于电解的硫酸锰溶液。结果表明:矿样10g,硫酸用量6mL,亚硫酸钠用量6g,90℃浸出100min,可以获得的96.42%锰浸出率;控制中和调浆终点pH=2.5,铁浸出率0.02%;控制除杂终点pH=4.5时,滤液达到合格电解液的标准。 相似文献