DESALINATION BEHAVIOR OF NATURAL ZEOLITE IN SEAWATER

Abstract

In recent years, it has been considered to secure water and food using seawater desalination
technology, and a new simple desalination material for reducing high concentration sodium chloride in
seawater is required. In this study, desalting agents were prepared from natural zeolite with addition of calcined
Ca-Fe type layered double hydroxide (LDH) to desalinate seawater for agricultural use. Mordenite type natural
zeolite from Fukushima, Japan was used. The salinity and pH of seawater used in this study were 3.61% and
8.0, respectively. When more than 250 g/L of natural zeolite was added, the salinity decreased from about
3.56% to about 2.92% (reduction : about 18.0%) after stirring for 1 h. With higher dosage of calcined Ca-Fe
LDH, the reduction time of salinity and the increase of pH became faster, while the reduction rate of salinity
was almost same and pH value increased. When the mixture was used at the mixing ratio of natural zeolite and
calcined Ca-Fe LDH was 5:4, the salinity decreased to 1.0% (reduction : about 70.0%) after stirring for 1 h,
and the pH of the solution increased to 9.0 - 9.7. Radish sprouts could be harvested using seawater treated with
a mixture of natural zeolite and calcined Ca-Fe LDH (5 : 4), while it was not possible to harvest using seawater
and seawater treated with natural zeolite with lower addition of calcined Ca-Fe LDH.