Three waste treatments for cockroaches and cockroaches
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And commonly used non-ferrous metal production compared to tantalum and niobium production plants generally smaller. A factory producing 150-200 tons of tantalum powder (already a large-scale factory in the industry), the raw material concentrate used in each year is generally in the range of 400-600t, and the absolute amount of waste gas and waste residue generated is small. Up to now, there is still a lack of efficient and economical processing methods in China. For a general exhaust gas (e.g., with an active adsorbent such as aluminum oxide adsorption) and condensation absorption method (the HF-containing gas through the first condenser graphite absorbed, and then the spent caustic lime drops or absorbed) by a conventional adsorption method. The amount of waste residue containing radioactive elements is not very prominent, and it is mainly concentrated in centralized storage. The following mainly introduces the treatment process of HF acid containing wastewater.
Nb - Ta smelter waste water treatment process and are generally treated with a combined two methods. For the wastewater containing both fluorine and uranium , the combined treatment is used, and the wastewater containing a certain amount of useful substances is treated separately.
   First, the merger process
The combined treatment has two kinds of adsorption methods and precipitation methods. Adsorption with an adsorbent can adsorb fluorine such as bentonite, marsh iron ore and uranium adsorbable adsorbents such as calcium phosphate, magnesium phosphate, coke, soft manganese ore adsorbing and removing fluorine, uranium and the like through physical adsorption and chemical Harmful Substance. The precipitation method uses a fluoride precipitating agent such as calcium oxide, aluminum sulfate, superphosphate, magnesium hydroxide, polyaluminum chloride, polyacrylamide or the like to precipitate fluoride (such as CaF 2 , Ca 5 F(PO 4 ) 3 ), The CaU 2 O 7 or the like is precipitated with a uranium precipitating agent such as calcium oxide, aluminum hydroxide, and fresh iron hydroxide.
  Second, separate processing
There are many treatment methods for various waste liquids.
(1) Quartz sand treatment raffinate recovers sodium fluorosilicate and sodium sulfate
The raffinate containing primarily F 1 - 150 ~ 200g / L , SO 4 2 - 460g / L, W2.9g / L, (Ta + Nb) 2 O 5 <1g / L, Fe18g / L and the like. The process flow is shown in Figure 1. The process is to add silica (an industrial quartz containing 97% SiO 2 ) to the raffinate to precipitate tungsten:
H 2 WO 2 F 4 +2HF+SiO 2 =H 2 WO 4 ↓+H 2 SiF 6
Filter out the H 2 WO 4 precipitate (the crude tungstic acid is dissolved by ammonia, evaporatively crystallized to produce ammonium paratungstate, and then calcined to obtain chemically pure tungsten trioxide), then add sodium base or sodium sulfate. Precipitating sodium fluorosilicate:
H 2 SiF 6 +2NaOH = Na 2 SiF 6 ↓ + 2H 2 O
Or H 2 SiF 6 +Na 2 SO 4 =Na 2 SiF 6 ↓+H 2 SO 4
Fig.1 Schematic diagram of recovery of sodium fluorosilicate by raffinate treatment
After recovering the sodium fluorosilicate, the solution was neutralized with NaOH to form sodium sulfate and crystallized by evaporation.
(2) Raffinate ammonia precipitation to recover cryolite
The process flow is shown in Figure 2. The process is to neutralize the raffinate with ammonia water to pH=7-8, so that tungsten precipitates as ammonium paratungstate (the solubility of ammonium paratungstate is only 0.064% when pH=7.3 and 17 °C); the solution after recovering ammonium paratungstate, adding aluminum sulfate The formation of ammonium fluoroaluminate, and then reacted with sodium chloride or sodium sulfate to form cryolite (sodium fluoroaluminate):
Al 2 (SO 4 ) 3 +12NH 4 F=2(NH 4 ) 3 AlF 6 +3(NH 4 ) 2 SO 4
(NH 4 ) 3 AlF 6 +3NaCl=Na 3 AlF 6 +3NH 4 Cl
2(NH 4 ) 3 AlF 6 +3Na 2 SO 4 =2Na 3 AlF 6 +3(NH 4 ) 2 SO 4
Figure 2 Schematic diagram of ammonia precipitation mother liquor treatment process
The mother liquor after recovering the cryolite can be evaporated to recover ammonium fluoride or ammonium sulfate.