PREPARATION OF DESALINATION AGENT FROM CA-TYPE CLAY MINERALS

Abstract

The desalination technology of seawater is considered to secure water and food in recent years, and a new simple desalting material to decrease the high concentration of sodium chloride in seawater is desired. In this study, preparation of the desalting agent from two Ca-type clay minerals, natural zeolite and Ca-Fe type layered double hydroxide (LDH), attempted to desalinate seawater for agricultural water[1][2][5]. Natural zeolites used in this study were mordenite-type zeolite from Fukushima prefecture, Japan and clinoptilolite-type zeolite from Kagoshima prefecture, Japan, and raw and Ca-substituted zeolites were used for seawater desalination[1][2][3][4][5]. Regardless of zeolite type, desalination behaviors of Ca-substituted zeolite were almost same as those of raw zeolite. The salinity and pH of seawater were 3.46% and 8.0, respectively, while clinoptilolite decreased the salinity to 3.20%, mordenite decreased to 2.09%, above 5.0 g/L zeolite addition. As increasing the Calcined Ca-Fe LDH addition to seawater, the salinity decreased to 3.3%, and pH of the solution increased to pH 11.5, and then became almost constant above 2.0 g/L addition of Calcined Ca-Fe LDH. As increasing the mixing ratio of Calcined Ca-Fe LDH to raw mordenite, the salinity decreased to 0.8% (79.2% reduction) while pH of the solution was neutral (about 7.6~8.0). Radish sprouts could be harvested using the seawater treated with a mixture of raw mordenite-type natural zeolite and Calcined Ca-Fe LDH, although those could not be harvested using seawater, the seawater treated with natural zeolite or Calcined Ca-Fe LDH.