Selective Removal of Calcium Ions from a Mixed Solution using Membrane Capacitive Seionization System

막결합 축전식 탈염장치를 이용한 혼합용액에서 칼슘이온의 선택적 제거

  • Kim, Yu-Jin (Department of Chemical Engineering, Kongju National University) ;
  • Choi, Jae-Hwan (Department of Chemical Engineering, Kongju National University)
  • Published : 2012.10.10


Possibility of the selective removal of $Ca^{2+}$ ions from a mixed solution of $Na^{+}$ and $Ca^{2+}$ ions using membrane capacitive deionization (MCDI) was investigated. Adsorption equilibrium experiments were conducted to determine the selectivity of the CMX cation-exchange membrane toward $Ca^{2+}$ ions. In addition, desalination experiments for a mixed solution (5 meq/L NaCl + 2 meq/L $CaCl_{2}$) were performed using an MCDI cell. The adsorption equilibrium of CMX membrane showed that the equivalent fraction of $Ca^{2+}$ ions in the solution and the CMX membrane were 28.6 and 87.2%, respectively, which indicates the CMX membrane's high selectivity toward $Ca^{2+}$ ions. Desalination experiments were performed by applying a constant current to the MCDI cell until the cell potential reached 1.0 V. The amount of ions adsorbed did not significantly change as the applied current was changed. However, the equivalent fractions of $Ca^{2+}$ ions among the adsorbed ions were inversely proportional to the applied currents: 81.4, 78.4, 77.0, and 74.5% at 200, 300, 500, and $700\;A/m^{2}$ of applied current density, respectively. This result is attributed to the increased fraction of $Ca^{2+}$ ions adsorbed by the CMX membrane at lower applied current densities.


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