Application of Electrochemical Ion Separation System for Removing Sodium Impurity to Produce High Purity KCl

Abstract

Potassium hydroxide (KOH) is widely used in various industrial fields, especially KOH used in electronic fields has a high economic value because it requires a high purity of 99% or more. At present, KOH is commercially mass-produced by an electrolysis process of potassium chloride (KCl), and thus, the purity of KOH produced is directly influenced by the purity of the raw KCl materials. In the case of industrial raw KCl materials, the impurities are removed by crystallization because they contain sodium ion impurities. However, crystallization has a problem in that a pretreatment process is required when the concentration of the sodium ion impurities is high. In this study, an electrochemical system using sodium manganese oxide (NMO) and potassium iron hexacyanoferrate (KFeHCF) which can remove sodium ions selectively from the raw KCl material used in the industrial process for KOH production was proposed. As the main results of this study, the NMO/KFeHCF system selectively removed approximately 36% of the sodium ion impurities in the industrial raw KCl solution after 3 cycles of operation. The purity of KCl was increased to 99.8% or more

thus, it was possible to produce high purity KOH with high economic value.