Preparation of cryolite from smelting fluorine-containing waste acid as raw material

Preparation of cryolite from smelting fluorine-containing waste acid as raw material

Cryolite is sodium fluoroaluminate, and its molecular formula is Na3AlF6. The excellent performance of cryolite is not only an indispensable co-solvent in the aluminum smelting industry, but also widely used in other industries, such as opacifiers in the enamel industry, wear-resistant fillers in the rubber and grinding wheel industries, and sunscreens in the glass industry.
  There are many methods for preparing cryolite, which can be divided into fluorite method, phosphate fertilizer by-product method, and fluorine-containing waste method according to different sources of fluorine.
  Using smelting fluorine-containing non-acid as raw material, cryolite is prepared through processes such as neutralization and removal of impurities, synthesis reaction, washing and drying. Under the optimal conditions of neutralization and impurity removal pH of 7.5, reaction pH of 8.0, feed ratio of Na:Al:F of 4:1:6, reaction temperature of 80℃, and reaction time of 60min, the fluorine recovery rate can be Up to 98.9%, the residual fluoride ion concentration can be reduced to 200mg·L-1; the quality of the produced cryolite product meets the requirements of GB/T4291-2007, and the sodium-aluminum substance ratio is 2.5, which belongs to the middle-molecular-weight cryolite.
  The process is simple in operation and low in cost. Treating 1m³ of smelting fluorine-containing waste acid, about 30kg of cryolite product can be obtained. The resource utilization of smelting fluorine-containing waste acid is realized, the difficulty in subsequent treatment of waste acid is reduced, and the environmental pollution caused by smelting waste acid is reduced.