Use of Ca-containing industrial waste brine for CO2 sequestration and recovery of NaCl and Na2SO4

Carbon dioxide (CO2) capture and sequestration play a vital role in global warming and climate change. The objective of this study was to use Ca-containing industrial waste brine for CO2 sequestration and recovery of NaCl and Na2SO4. The following operating parameters were investigated: pH, NaCl concentration, CO2 injection time, CO2 inflow rate, and temperature. The phi-pH diagrams of the Ca-Mg-CO32--H2O system revealed that the maximum CO2 dissolution efficiency in brine occurred at pH 10.7-14.0. The decalcification efficiency reached 99.0% at the optimal conditions, which were a brine pH of 11.5, a CO2 injection time of 30 min, a CO2 injection velocity of 1.5 L/min, a temperature of 35 degrees C, and a stirrer speed of 300 rpm. The CO2 capture capacity of Ca -containing industrial waste brine was about 1.29 kg CO2 / m3 Ca-containing waste brine. The sediments pro-duced in the CO2 sequestration process are composed of calcite, which is thermodynamically stable and has economic value. Na2SO4 and NaCl crystals with a narrow size distribution and good anti-caking properties were produced from the refined brine using five-effect evaporation crystallization. These observations provide further understanding and guidance for CO2 capture and the utilization of high salinity wastewater.