APT Crystallization Liquor Treatment -- Nano Membrane Filtration
The crystalization method of evaporation and extraction method in the preparation of APT will produce crystallization liquor, leaving about 5% -10% of the WO3 and part of the S, P, As, Mo, K, Na and other impurities.
Since the APT crystallized liquor contains a large number of impurity elements, it can not be directly returned to the process, in order to improve the metal recycle, it is necessary to set the auxiliary process to recycle the of WO3.
Due to the low energy consumption of membrane separation technology, it’s easy to achieve continuous operation and management, the process is easy to enlarge, the equipment is compact, it occupies a limited area and easy to use with other processes. In recent years, it widely attracted by the industry. Nano-Membrane filtration method is based on nano filtration equipment and put forward on the basis of great achievements.
Nano membrane filtration was developed since the 1980 s, a new type of pressure driven membrane, its property between ultra filtration and reverse osmosis membranes, using nano filtration membrane (membrane aperture at the nanoscale range), the price of 2 and multivalent ions and the molecular weight between 200-1000, the characteristics of the substance has a higher removal efficiency of chloride ions from the liquor and containing tungsten ion separation, so as to realize the recycle of tungsten and ammonium chloride in the liquor.
Since the tungsten in the liquor is present as WO42-, in order to allow chloride ions and tungsten ions to be better separated, it is necessary to use tungsten in the acidic conditions in the form of partial tungstate, the liquor is acidified and then ionized. In nano filtration method, concentration, pressure is the key process parameters, the lower the pressure and the concentration, the higher the dechlorination rate, the lower the tungsten loss . But low concentration and pressure will make the nano filtration membrane permeability and dechlorination rate decreased, energy consumption increases. Therefore, from the comprehensive benefits, it should increase the membrane area, and adopt the appropriate material liquid concentration, pressure in order to improve the dechlorination rate.
Nanofiltration has strong adaptability. Compared with other methods, nano membrane filtration method also has the advantages of short process and and small consumption, more importantly, in the process of ammonium paratungstate crystallization liquor treatment, it almost has no additional pollution of waste water.
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