Preparation of mineral source water from deep sea water: reduction of sulfate ion using Selemion ASV membrane

• Main Authors: Hsiang-Yung Lu, 呂翔詠
• Other Authors: Sung-Hwa Lin
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/34979792300144194006

碩士 === 國立宜蘭大學 === 化學工程與材料工程學系碩士班 === 99 === Preparing the regulated, potable mineral water from the deep sea water (DSW) becomes more and more prevailing in the recent decades, for DSW is of purity, free from the pollutant from the land, and rich in the vital ions, like the magnesium ion and the calcium ion. However, the high concentration of sulfate ion in DSW limits considerably its potable use. In this study, using a laboratory-scale electrodialysis (ED) apparatus, we investigate the performance of a commercial monovalent anion permselective membrane, Selemion ASV anion-exchange membrane, which is seldom studied in the literature, in the reduction of sulfate ion for the produced mineral source water. For efficiency, we use the highly concentrated brine from DSW, which has a salinity of about 15%, as the raw material water in ED process. The emphasis of present study is put on the interrelation between the separation of sulfate ion from the chloride ion, and both ED duration and the applied direct current (DC) voltage. The experimental results show that: (1) after an ascending stage (about 60 minutes), the electrical current (also ions flux) reaches a lower/higher plateau for lower/higher voltage, and it may approach to zero before the end of ED process for higher voltage; (2) the liquid volume change during ED process is dominated by both the ions transport and the electroosmosis for higher voltage; (3) the transport of chloride ions is approximately a linear function of ED duration; (4) the chloride ions show almost complete blocking effect for the transport of sulfate ions, and it is presumed that, the pore size of permselective layer coating on the Selemion ASV membrane surface is quite close to the size of sulfate ion, and hence, when the ions travel in these pores of permselective layer, the smaller, predominant chloride ions are very likely to block the sulfate ions from their entrance; (5) using the optimization, the optimal operational conditions of ED process can be determined under some criteria, including high chloride ion production, low sulfate ion content, and low electrical energy consumption.