ABSTRACT
According to the new regulations of Ministry of Environmental Protection in China, sewage zero discharge is enforced in tungsten smelting. Howerver, the major process of tungsten smelting[3-6] is high alkali decomposition combined with ion exchange, which brings many environmental problems. On the one hand, there are 21,300 tons of caustic soda and 10,200 tons of ammonia nitrogen which are released into the environment, and the pH value and the ammonia nitrogen concentration in the sewage is 13 an 2000 mg ⋅ L−1, which are 10,000 times and 130 times higher than those of the national standard respectively. On the other hand, the solutions
after impurity removed. Thus, the process of ion exchange can be omitted and the above problems can be settled. According to that, some experiments were made 8.0 times Ammonium phosphate dosage to stoichiometry, 3 hours’ reactive time under the temperature of 180 °C, but the the WO3 extraction is only 55%. The possible reason is that, the conditions can not completely overcome the apparent activation energy of scheelite. Therefore, in order to increases the WO3 extraction, strengthening leaching is needed to some extent. Mechanical activation is widely used in intensification of leaching mineral, which can make the distortion of the material microstructure under the action of mechanical force, which thereby increases the chemical activity of the materials. Mechanical activation is also frequently used to strengthen tungsten ores leaching process, and the WO3 extraction can be improved obviously.[9-11]
Therefore, with the help of mechanical activation, a novel process is put forward to decompose scheelite with ammonium phosphate in this paper. The relative experimental parameters such as mechanical activation time, agitation speed, ammonium phosphate dosage, reactive time, temperature, concentration of ammonia water and ratio of liquid to solid on the process would be investigated in the present study.
