Recovery of NaCl and Na2SO4 from high salinity brine by purification and evaporation

High salinity brine is the main resource for NaCl and Na2SO4 . An industrial production test and application for Na2CO3-NaOH brine purification methods were carried out and operated for different periods. The total concentration of Ca2+ and Mg2+ was reduced from 513.49 mg/L to 12.01 mg/L at the optimal doses of NaOH = 0.25 g/L and Na2CO3= 1.3 g/L. This extended the production periods from 60 to 70 days to 90-100 days during the industrial application. In addition, the degree of CO32- accumulation in the circulating feed brine was decreased, and the deposition of CaCO3 was inhibited. Narrow NaCl and Na2SO4 crystals with good anti-caking properties were prepared from high salinity brine by regulating the evaporation temperature and pressure in a multi-effect evaporation system. Moreover, the crystal growth direction of NaCl and Na2SO4 was observed by optical microscopy at different supersaturation degrees. The long-term, low-energy operation of brine purification and evaporative crystallization industrial production were realized, which are of great significance to the treatment of salinity wastewater in the chemical industry and metallurgy fields.