Clean (“Green”) Ion-Exchange Technologies. 4. High-Ca-Selectivity Ion-Exchange Material for Self-Sustaining Decalcification of Mineralized Waters Process

This paper (the fourth in a series) reports the results of a theoretical and experimental study of the decalcification of seawater on different ion-exchange sorbents by simultaneous use of electroselectivity reversal and ion-exchange isothermal supersaturation (IXISS) effects. A detailed evaluation of the influence of the sorbent properties on the efficiency of the IXISS-based self-sustaining seawater decalcification process was carried out through a series of computer experiments using a mathematical model of the dynamics of ion exchange. It was found that the best sorbent to be used in the process is a modified A-type zeolite. The modification of the zeolite includes sequential treatment of the initial ion exchanger with dilute magnesium-containing solution (or seawater) and concentrated sodium salt solution. The first treatment was carried out at elevated temperature [15−20 °C higher than the temperature at which the modified zeolite (MZ) is expected to be used, Tex], and the second was performed at Tex. The complete regeneration of the MZ after the calcium sorption cycle was carried out with the calcium-free brine produced by the seawater desalination unit. The process is continuous and operates in the closed-cycle mode.Part of this work was supported by Research Grants ND-2000 and ND-2300 from the International Science Foundation and by grants from the Science and Technology Programs of Russian Federation “Global Ocean” (Grant 02.08.1) and the Russian Foundation for Basic Research (Grant 02-03-33144). The Ministry of Science and Technology of Spain is acknowledged with thanks for the financial support of D.M. within the Program “Ramon y Cajal”.Peer reviewe

Clean (“Green”) Ion-Exchange Technologies. 4. High-Ca-Selectivity Ion-Exchange Material for Self-Sustaining Decalcification of Mineralized Waters Process

This paper (the fourth in a series) reports the results of a theoretical and experimental study of the decalcification of seawater on different ion-exchange sorbents by simultaneous use of electroselectivity reversal and ion-exchange isothermal supersaturation (IXISS) effects. A detailed evaluation of the influence of the sorbent properties on the efficiency of the IXISS-based self-sustaining seawater decalcification process was carried out through a series of computer experiments using a mathematical model of the dynamics of ion exchange. It was found that the best sorbent to be used in the process is a modified A-type zeolite. The modification of the zeolite includes sequential treatment of the initial ion exchanger with dilute magnesium-containing solution (or seawater) and concentrated sodium salt solution. The first treatment was carried out at elevated temperature [15−20 °C higher than the temperature at which the modified zeolite (MZ) is expected to be used, Tex], and the second was performed at Tex. The complete regeneration of the MZ after the calcium sorption cycle was carried out with the calcium-free brine produced by the seawater desalination unit. The process is continuous and operates in the closed-cycle mode.Part of this work was supported by Research Grants ND-2000 and ND-2300 from the International Science Foundation and by grants from the Science and Technology Programs of Russian Federation “Global Ocean” (Grant 02.08.1) and the Russian Foundation for Basic Research (Grant 02-03-33144). The Ministry of Science and Technology of Spain is acknowledged with thanks for the financial support of D.M. within the Program “Ramon y Cajal”.Peer reviewe