碱熔-水浸法从钼精矿焙烧烟灰中回收铼和钼

Recovery of Rhenium and Molybdenum from Dust of Roasted Molybdenum Concentrate by Oxidized Alkali Fusion Followed by Water Leaching

针对目前采用的沉淀法和直接浸出法从钼精矿焙烧烟灰中回收铼和钼回收率较低的问题，提出通过添加硝酸钠和碳酸钠碱熔实现铼和钼物相的转化，然后采用水浸法回收铼和钼。考察了硝酸钠与烟灰质量比、碳酸钠与烟灰质量比、碱熔时间和碱熔温度对碱熔过程中铼和钼转化率的影响；采用差热分析．热重法（DTA-TG）和x射线衍射（XRD）分析了钼的反应过程和相变行为；探讨了双氧水浓度、浸出温度、浸出时间和液固比对水浸过程中铼和钼浸出率的影响。结果表明，合适的碱熔条件为硝酸钠和碳酸钠加入量均为烟灰质量的60％，碱熔时间3h、碱熔温度500℃，铼和钼的转化率分别达到93．5％和96．3％；随着碱熔温度的提高，产物中钼的物相由Na2Mo2O7向Na2MoO4转变，在500oC时Na2MoO4峰最强，继续提高碱熔温度时，Na2MiO4峰减弱，Si02变得活跃并与氧化钙和氧化钠结合生成硅酸盐；合适的浸出条件是双氧水浓度10％、浸出温度70℃、浸出时间2h、液固比5：1，铼和钼的浸出率分别达到93．2％和95．3％。

In view of low extraction rates of rhenium and molybdenum by precipitation and direct leaching from dust of roasted molybde- num concentrate, a novel process of oxidized alkali fusion with sodium nitrate and sodium carbonate followed by water leaching was pro- posed. The effects of ratios of sodium nitrate and sodium carbonate to dust of roasted molybdenum concentrate, alkali fusion time and al- kali fusion temperature on the transformation rates of rhenium and molybdenum were investigated. The differential thermal analysis-ther- mogratimetry （DTA-TG） and X-ray diffraction （XRD） analysis were adopted to analyze the reaction procedure and reveal phase transfor- mation behavior of molybdenum. Meanwhile, the influences of different process parameters （ such as concentration of hydrogen peroxide, leaching temperature, leaching time and liquid-solid ratio） on leaching efficiency were studied. The results showed that the preferable transformation rates of rhenium and molybdenum were 93.5% and 96.3% , respectively, when ratios of sodium nitrate and sodium car- bonate to dust of roasted molybdenum concentrate were 60% , alkali fusion time was 3 h and alkali fusion temperature was 500 %. Spe- cifically, with the increase of alkali fusion temperature, the phase of molybdenum transformed from Na2 Mo2 07 to Na2 MoO4 , and the XRD peaks of Na2 MoO4 were the most significant at 500 %. However, further increase of temperature weakened the XRD peaks of Na2 MOO4, activated silica, calcium oxide and sodium oxide to form silicates. The leaching rates of rhenium and molybdenum were 93.2% and 95.3%, respectively, when the concentration of hydrogen peroxide was 10%, leaching temperature was 70 ℃, leaching time was 2 h and liquid-solid ratio was 5： 1.