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

Abstract

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.