Seawater desalination by gas hydrate process and removal characteristics of dissolved ions (Na~+,K~+, Mg~(2+), Ca~(2+), B~(3+),'Cl~-, SO4~(2-))

摘要

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~+, Mg~(2+), Ca~(2+), and B~(3+)) and anions (CI- and SO4~(2-)) 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~+ RsMg~(2+) ?Ca~(2+) >B~(3+)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.