Chen GZ, Fray DJ, Farthing TW
Department of Materials Science and Metallurgy, University of Cambridge, UK.
Nature. 2000 Sep 21;407(6802):361-4. doi: 10.1038/35030069.
Many reactive metals are difficult to prepare in pure form without complicated and expensive procedures. Although titanium has many desirable properties (it is light, strong and corrosion-resistant), its use has been restricted because of its high processing cost. In the current pyrometallurgical process--the Kroll process--the titanium minerals rutile and ilmenite are carbochlorinated to remove oxygen, iron and other impurities, producing a TiCl4 vapour. This is then reduced to titanium metal by magnesium metal; the by-product MgCl2 is removed by vacuum distillation. The prediction that this process would be replaced by an electrochemical route has not been fulfilled; attempts involving the electro-deposition of titanium from ionic solutions have been hampered by difficulties in eliminating the redox cycling of multivalent titanium ions and in handling very reactive dendritic products. Here we report an electrochemical method for the direct reduction of solid TiO2, in which the oxygen is ionized, dissolved in a molten salt and discharged at the anode, leaving pure titanium at the cathode. The simplicity and rapidity of this process compared to conventional routes should result in reduced production costs and the approach should be applicable to a wide range of metal oxides.
许多活性金属若不采用复杂且昂贵的工艺，就难以制备出纯净的形态。尽管钛具备诸多优良特性（质轻、强度高且耐腐蚀），但其应用却因加工成本高昂而受到限制。在当前的火法冶金工艺——克罗尔法中，钛矿物金红石和钛铁矿通过碳氯化反应去除氧、铁及其他杂质，生成四氯化钛蒸气。接着，用镁金属将其还原为金属钛；副产物氯化镁则通过真空蒸馏去除。此前预测该工艺将被电化学方法取代，但这一预测尚未实现；从离子溶液中电沉积钛的尝试，因难以消除多价钛离子的氧化还原循环以及处理极具活性的树枝状产物而受阻。在此，我们报告一种直接还原固态二氧化钛的电化学方法，其中氧被电离，溶解在熔盐中并在阳极放电，而在阴极留下纯钛。与传统方法相比，该工艺的简便性和快速性应能降低生产成本，且此方法应适用于多种金属氧化物。
