Neutralization and precipitation method
This is a waste water treatment method commonly used in tungsten smelting at present. By adding alkaline substances (such as sodium hydroxide, lime, etc.) to neutralize the acidic substances in the wastewater, the heavy metal ions (such as Pb2+, Cd2+, etc.) in the wastewater form insoluble precipitates, thus achieving the purpose of purifying the wastewater. However, although this treatment method can remove most of the heavy metal ions in the wastewater, the treated wastewater will still contain a large amount of C1-, which may form secondary pollution.
Evaporation and crystallization method
This method is especially suitable for treating wastewater from the production of APT (ammonium paratungstate) and ammonium metatungstate (AMT). By means of evaporation crystallization, solutes (such as sodium sulfate, etc.) in the wastewater are precipitated out in the form of crystals, thus realizing the purification and recovery of wastewater. The evaporation crystallization method can efficiently remove solutes from wastewater and recover valuable substances at the same time, which has high economic and environmental benefits.Sodium sulfate in APT wastewater is crystallized at working conditions higher than 32.6°C, which is convenient for subsequent packaging and storage.
Ion exchange method
Ion exchange method is mainly used to recover sodium tungstate in wastewater. The sodium tungstate in wastewater is adsorbed by specific resin, and then drenched with sodium hydroxide solution, so that the sodium tungstate is drenched down to the next purification process. This method can effectively recover sodium tungstate in wastewater, reduce the production cost, and also reduce the pollutant content in wastewater.
Reverse osmosis process
Reverse osmosis process is a highly efficient wastewater treatment technology that can remove most of the dissolved substances and ions in wastewater. For APT production wastewater, which is a highly concentrated saline wastewater, the reverse osmosis process suffers from low recovery rate and high operating pressure, and the treated wastewater may contain high concentrations of inorganic salts that require further treatment.
The wastewater treatment of ammonium metatungstate usually adopts the methods of neutralization and precipitation, evaporation and crystallization, ion exchange and reverse osmosis process. Among them, the evaporation crystallization method is widely used in the treatment of APT production wastewater because of its high efficiency and environmental friendliness. In practical application, it is necessary to choose the appropriate treatment method according to the specific composition of the wastewater and the treatment requirements in order to achieve the best wastewater treatment effect.
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