Thermally regenerable ion-exchange resins. I the encapsulation of polyamine microparticles in a polyacid matrix

Study of a new process for the efficient regeneration of ion exchange resins

“…This process was originally based on the use of a physical mixture of weakly basic and weakly acidic ion-exchange resin beads. It was later employed for resins containing both weak acid and weak base components within each bead in the so-called 'plum pudding' structure [7,8]. These resins are thermally regenerable, that is, they are capable of removing salts from an aqueous solution by sorption at ambient temperatures and at higher temperatures their sorption capacity is significantly reduced [11].…”

“…The "Plum pudding" resin structure, which is prepared by embedding microparticles of polyamines and microparticles of polyacids in a water and salt permeable matrix, has been discussed by Bolto and Jackson [8]; who also described the disadvantage of the presence of a high proportion of inert polymeric matrix material, which tends to limit the thermally regenerable capacity of a particular resin. Studies have been carried out by Hatch [25], Bolto and Jackson [8] and Chanda et al [16] to overcome this issue.…”

“…Because of this such desalting processes result in high operating costs and create substantial volumes of by-product saline waste and require high levels of acid and base consumption. To overcome these issues new methods to regenerate ion exchange resins by other means, such as heat energy (Sirotherm process), electrical energy (electrodialysis) or mechanical energy (piezodialysis) have been studied [6][7][8][9][10]. The "Sirotherm" process [6] was developed by the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Melbourne, Australia.…”

A thermally regenerable composite sorbent of crosslinked poly(acrylic acid) and ethoxylated polyethyleneimine for water desalination by Sirotherm process

“…According to Bolto and Jackson,6 “thermally regenerable ion‐exchange resins must be composed of discrete acidic and basic domains grouped together in a porous particle of the conventional size for ion‐exchange resins of 0.3–1.2 mm”. Depending on the method of manufacture, two extreme types of structure for such composite resins may be envisaged.…”

“…A so‐called “mosaic structure” consisting of a mosaic of acidic and basic domains of 0.01–5‐μm size would be expected to result from the polymerization of a mixture of monomers 7. In such a structure, a larger amount of internal salt formation ( CO··· + NH) between the carboxylate and protonated amino groups, which is detrimental to the Sirotherm process, would be expected 6…”