| Molybdenum and rhenium both have excellent physical and chemical properties, and they are also significantly strategic material in the21st century. This dissertation focused on separation of molybdenum and rhenium from Mo-Fe alloy dust and spraying waste water of molybdenum incineration. It is both theoretically and industrially significant with the following results:(1) This dissertation firstly studied the determination method of molybdenum by ammonium thiocyanate spectrophotometry detection based on available standard method. The results showed that the molybdenum content obeyed the Beer’s Law in the range of10-300μｇ/25mL. The deviation of the experimental results was±4%, and the recovery rate was between98.3and103.0%by addition of standard substance. Compared with the other similar research, the method was proved to be a simple and rapid method in molybdenum determination with a high accuracy and wide linear range.(2) The best condition of lixiviating Mo-Fe dust was confirmed. After lixiviation by sulphate acid, only a little molybdenum existed in lixiviating solution as molybdenum acid ions, while most of the molybdenum existed in solid molybdenum acid. Total recovery rate of molybdenum was affected by the two sections above. And the best engineering condition of lixiviating molybdenum dust by sulphate acid was confirmed as follows:solid-liquid ratio (ms:Vl) was1:3, H2SO4concentration was9.09%, heating time was3h, temperature was80℃, and recovery rate was99.1%.The dynamic mechanism of the lixiviation process was discussed, which showed the linear relationship of1-(1-α)1/3and time, and the dynamic equation was obtained as follows:1-(1-a)1/3=1.34x102·e-RT·t. The apparent activation energy was calculated as E,=29.01kJ-mol’1. (3) The molybdenum extraction and stripping condition of Mo-Fe alloy dust lixiviation liquid was investigated, and the best condition was obtained as follows: extraction temperature was30℃, phase ratio(Vw/Vo) was3:1, H2SO4concentration was0.13mol·L-1, equilibrium time was5min, extraction serial was3, and extraction rate of Molybdenum was99.35%. In the stripping process, ammonia was taken as Stripping agent in the condition of3serials stripping, with a phase ratio(Vw/Vo) of1:1, temperature of30℃, time of5min, stripping rate of99.56%, it showed high molybdenum selectivity.(4) The extraction kinetics of molybdenum (VI) with trialkyl amine has been investigated by constant interfacial cell with laminar flow. The influences of stirring speed, temperature and concentrations of extractant on the extraction rate were studied. It can be concluded that the mass transfer process was a diffusion controlled when the stirring speed was less than250r-min-1and interfacial chemical reaction chemical when the stirring speed was higher than250r-min-1. The extraction rate equation of Re(VII)-N235in sulfuric acid system was:(5) The preparation condition of ammonia molybdenate was also investigated. The lixiviation rate of molybdenum in molybdenum acid mud rose with the increase of liquid-solid ratio, amount of ammonia and temperature. And the ammonia molybdenate was obtained by mixing stripping solution and ammonia lixiviation of molybdenum acid mud. The impurity of Si, As, P and SO42-can be removed by adding Mg(NO3)2and Ba(OH)2solutions, and the ammonia molybdenate product was obtained by neutralization with nitric acid.(6) The production line of extraction of molybdenum from Mo-Fe alloy dust was built up. On the basis of laboratory results and theoretical research, the new production line was built up with the output of1000t per year, which can also produce271.43t of ammonia molybdenum with a high quality according to GB/T3460-2007, and the recovery rate was increased by10%compared with the existing technique. The research has prominent economical and environmental values. One patent has also been obtained with independent intellectual property rights.(7) The spectrophotometer method of determining rhenium was set up, which can easily determine the rhenium content in specimen. It showed that when m(Mo): m(Re)=100:l, and SnCl2solution (5%) added2.0mL,the concentration of rhenium could be determined. The Beer’s law was obeyed in the range of1-10μg/10mL. The relative equation was as bellows: y=0.0595Cμg10ml+0.1466, with r=0.9991, and recovery rate was between98.7%-102.5%by addition of standard substance.(8) New technology of separation of molybdenum and rhenium has been set up. Also, a new technology of separating molybdenum and rhenium by resin D314was performed in this dissertation. The new technology took CaO as precipitator, which can increase adsorption rate of rhenium to99%. The desorption rate of rhenium in the resin had been increased to98%, using ammonia as a desorption agent. The enrichment of rhenium can reach20times, which have the highest recovery rate. The absorption mechanisms of molybdenum and rhenium in resin D314were investigated, the absorption process was diffusion controlled and the absorption rate constant was1.79mL-mg-1-min-1,0.212mL·mg-1·min-1·respectively. The technology of separation of molybdenum and rhenium was set up in Yangjiazhangzi economic development district, which has produced67.391kg of ammonium perrhenate (46.5kg based on Re). This research has remarkable economical and environmental value. |
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