Seawater desalination by gas hydrate process and removal characteristics of dissolved ions (Na+, K+, Mg2+, Ca2+, B3+, Cl-, SO42-)

In order to evaluate hydrate-based desalination (HBD), experiments with seawater samples were carried out at various conditions (i.e. hydraulic pressure, washing step, and hydrate-forming gas). Before and after the hydrate process, cations (Na+, K+, Mg2+, Ca2+, and B3+) and anions (Cl- and SO42-) were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) and ion chromatography (IC). In a single stage of CO2 hydrate process without any pretreatment, 71%-94% of each cation was removed in the following order: K+ > Na+ approximate to Mg2+ approximate to Ca2+ > B3+ and 73%-83% of each anion was removed. When the brines on the surface of hydrate pellets were removed, the ion removal efficiency increased above 4%. It was also found that the desalting efficiency depended on the hydrate-forming gas (CO2 > CH4) and the hydraulic pressure (6-10 MPa) to produce hydrate pellets. In this study, the removal efficiency of cations and anions in a real seawater sample using HBD processes were reported for the first time. (C) 2014 Elsevier B.V. All rights reserved.