Separation Of Calcium And Magnesium Ions In The Brine By Dual Carriers Emulsion Liquid Membrane

Desalination brine contains high concentration of calcium and magnesium. However, the direct discharge can not only pollute the surrounding environment, but also the waste of resources in the sea. Due to the similar physical and chemical properties of calcium and magnesium ions, the current technology can not effectively separated of them. Because of its high selectivity and fast mass transfer and so on, the technology of the emulsion liquid membrane, which is considered as an effective separation technique, is widely concerned in the separation of metal ions. This paper chose D2EHPA and DB18C6 as the mobile carriers, constructed a dual-carriers emulsion system, and collaboratively separated Ca2+ and Mg2+ in brine by selectivity of them. Meanwhile, the study verified the separation of two kinds of ions by dual carriers emulsion with multiple factors.Through the comparison with demulsification ratio of emulsion and preliminary extraction, this study chose dichloromethane as the oil phase, sodium oxalate solution as the internal phase. Based on viscosity and demulsification ratio of emulsion, this paper had studied the effects of ratio of oil to water, the content of surfactant, the concentration of internal phase and two kinds of carrier on the stability of emulsion. The results show that, with the decreasing ratio of oil to water, the demulsification ratio and change of viscosity were enlarged during 30 min, while the viscosity of emulsion with the oil to water of 1:1 reduced 23 mPa·s, and the demulsification ratio was 0.45%. The higher the surfactant content, the smaller the demulsification ratio, the better the stability of emulsion. With the concentration of Na2C2O4 decreased, the stability of emulsion increased, and demulsification ratio reduced to 1.7%(0.18 M Na2C2O4) from 2.5% (0.2 M Na2C2O4). Compared with DB18C6, the demulsification ratio of emulsion with D2EHPA as the single carrier slightly increased 0.8%, but the extractive process was not obvious effected. The optimized emulsion stability condition:O/W was 1:1, the content of Span80 was 6%, D2EHPA was 4%, and the concentration of DB18C6 was 0.015 mol/L.In the study, the extraction and separation effect of Ca2+ and Mg2+ were analyzed in two kinds of emulsion liquid system which D2EHPA and DB18C6 respectively as single carrier and both as the carriers of emulsion. The highest extraction ratio of calcium was 92.12% when D2EHPA was the carrier, while the extraction ratio only 66.72% when DB18C6 was the single carrier. In the dual carrier emulsion the extraction ratio of Ca2+ reached 70% at 3 minute, and reached 99.37% after 30 minutes. The synergistic factor of dual carriers of Ca2+ reached to more than 11, while that of Mg2+ was only 17.89% and the synergistic factor was less than 0.7. The calcium was almost completely separated. The operating conditions of the optimized results were:pH of the external phase was 9.5, the composition of emulsion was: 90% CH2Cl2,6% Span80,4% D2EHPA,0.017 mol/L DB18C6,0.18 mol/L Na2C2O4, ratio of oil to water was 1:2.