A method based on equilibrium theory for a correct choice of a cationic resin in sea water softening

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

“…Curve 1 corresponds to (K ˜Mg Ca ) 2 ) R Mg Ca ) 2.85 reported by Klein et al 16 The point (+) on this curve corresponds to K ˜Na Ca (s) ) 1.4, which is also known from the literature. 16 The points on curves 2, 3, and 5 correspond to the following R Mg Ca and K ˜Na Ca (s) values: 4.9 and 2.0, 12.7 and 2.4, and 28.2 and 2.05, respectively, as reported by Barba et al 19 Estimation of the economic aspects of the selfsustaining seawater decalcification process permits the conclusion that an economically reasonable process can be designed at E ω > 8/(3φ -1) (h -1 ). For example, at φ ) 0.75, E ω must be >6.4.…”

“…The curves shown in Figure 2 are the cross sections of three-dimensional surfaces that pass through the points corresponding to the selectivity coefficients of the sorbents proposed earlier and developed in this work. Thus, curves 1 (Dowex-50 × 8), 2, 3, and 5 (activite resins) in Figure 2 correspond to the sorbents that were suggested for use in the seawater decalcification process by Klein et al 16 and Barba et al 19 Curve 4 refers to the modified zeolite (MZ) of type A developed in this work. Curve 1 corresponds to (K Mg Ca ) 2 ) R Mg Ca ) 2.85 reported by Klein et al 16 The point (+) on this curve corresponds to K Na Ca (s) ) 1.4, which is also known from the literature.…”

“…Specially synthesized IE resins, namely, activite cationic resins, which are analogous to sulfonated poly(styrene-divinylbenzene) (PS-DVB) copolymers but contain more than one (1.5-2.0) sulfonic acid group per aromatic ring in their structure, were proposed for this purpose. 19 These sorbents exhibit selectivity factor (R Mg Ca ) values from several tens to 100. However, these ion exchangers still remain quite costly and scarcely available.…”

Mixed Anion Exchange Resins for Tunable Control of Sulfate–Chloride Selectivity for Sustainable Membrane Pretreatment

“…In this study, we present a synergy between the anion exchange and the RO process where no external regenerant is necessary and the precipitation of calcium sulfate can be completely avoided even with an increase in product water recovery. In the past, researchers tried to use cation exchange resins to avoid precipitation by controlling Ca/Na selectivity while achieving self-regeneration. − However, that goal has not been achieved as yet. Commercially available anion exchange resins have appropriate composition variables, namely, functional group, matrix, and basicity to tailor sulfate/chloride selectivity as needed.…”

Investigation of cyclic self-sustaining ion exchange process for softening water solutions on the basis of mathematical modeling

“…Ion exchange resins, namely, Activite and Taylor-made cationic exchangers were proposed for this purpose. These cationic exchangers contained more than one sulfonic acid group per aromatic ring in their structure [6], as well as specially modified inorganic polymers like artificial zeolites of A-type [7]. Further computation of successive cycles of SS-process with the use of a general dynamic model at a different variety of parameters allowed clarification of the requirements to sorbent characteristics and operation conditions [7][8][9].…”