Ion exchange resin particles

Bed A mass of ion-exchange resin particles contained in a column. Bed depth The height of the resinous material in the column after the exchanger has been properly conditioned for effective operation. Bed expansion The effect produced during backwashing when the resin particles become separated and rise in the column. The... 

Kim, H.-B., Habuchi, S., and Kitamura, N., Dynamic fluorescence spectroscopic study on the microstructures in ion-exchange resin particles, Anal. Chem., 71, 842, 1999. 

By administering both sizes of formulation simultaneously, a better discrimination of relative transit of the two phases can be made. In a cohort of 22 healthy young volunteers, an enteric-coated capsule was administered which contained tablets ("mTc-labeled 5 mm or 8.4 mm diameter) together with pellets (mIn-labeled 0.2 mm ion-exchange resin particles). The unit delivered the radiopharmaceuticals simultaneously to the ileocecal junction [44]. Under control conditions, no difference was observed between the rate of transit through the ascending colon of 0.2-mm particles versus 5-mm tablets, or 0.2-mm particles versus 8.4-mm tablets. The mean period of residence of 50% of the administered 0.2-mm particles in the ascending colon was 11.0 + 4.0 h. 

Figures 7 and 8 show this ion-exchange resin particle was very elastic up to a deformation of 46%. The contact radius and lateral extension of the particle were also measured as a function of time (data not shown),...

Figure 7 Images of an ion-exchange resin particle (DOWEX 1X8-200, Sigma-Aldrich, UK) compressed to different deformations (values in brackets) and then released. The particle diameter was 163 pm (images provided by T. Liu, University of Birmingham, UK).

So far, there is only one microparticulate ocular delivery system on the market. Betoptic S is obtained by binding of betaxolol to ion exchange resin particles. Betop-tic S 0.25% was found to be bioequivalent to the Betoptic 0.5% solution in lowering the intraocular pressure [208],... 

A interesting new process for the removal of metallic (Cu(II)) compounds in the treatment of industrial waste waters has been proposed by Flores and Cabassud [2.447, 2.448]. It consists of a membrane reactor with a moving-bed of porous ion-exchange resin particles. These authors have carried out laboratory experiments with this novel membrane reactor process. Prior to the initiation of the experiments a number of cationic resins were screened, and IRP 69, a resin whith a small particle diameter and high exchange rate, was chosen for the study. For these resin particles, the influence of stirring velocity and tern-... 

Moving-bed ion exchange. Ion-exchange resin particles are small spherical beads. These can be readily moved out of an ion-exchange column with up-flowing liquid and pumped with the liquid to another tank or column. Transport of resin is used in two types of uranium extraction processes, (1) the moving-bed type and (2) the continuous RIP type. 

Heterogeneous. Ion-exchange resin particles dispersed in polymer film. 

Example 12.1. Figure 12.3 shows a water softener in which water trickles by gravity over a bed of spherical ion-exchange resin particles, each 0.05 in in diameter. The bed has a porosity of 0.33. Calculate the volumetric flow rate of water. 

BED - A mass of ion-exchange resin particles contained in a column. 

In this section, (i) relationship between formation/extinction of voids and incorporation of ion-exchange resin particles into BR rubber and (ii) effect of fill factor and rotor design on mixing behavior were investigated (Toh et al., 1984 Gondoh et al., 1995). 

Fig. 11 Incorporation and dispersion processes of ion-exchange resin particles into BR rubber observed from the front window of the mixer with the (g) type rotor.

Mass transfer in a fluid flowing around solid particles, e.g., catalyst particles, ion exchange resins, particles of a dissolving solid. 

The distribution equilibrium of a weak electrolyte or a nonelectrolytic solute i between an external solution (w) (generally an aqueous solution) and the ion exchange resin particles (j = fi) is usually described by a distribution coefficient ... 

Often, the concentration Cm is described in terms of moles of species i per unit weight of ion exchange resin particle or per unit weight of solvent in the resin particle. In order to make Km dimensionless, C, should have similar units. Sometimes Km is constant for example, acetic acid has a linear isotherm in styrene-type cation exchangers (Helfferich, 1962, p. 126). In general there are a variety of interactions between the solute and the resin system, leading to a complex behavior. 

Such a scheme was proposed by Boyd et al. (1947). Since step (3) is instantaneous, we need only consider steps (1), (2), (4) and (5). However, there are essentially two types of resistances here steps (1) and (5) account for diffusion through the Uquid film on the outside of the resin particle, whereas steps (2) and (4) describe the diffusion of counterions through the pores of the ion exchange resin particle. When steps (1) and (5) control the exchange rate, the ion exchange is said to be film diffusion controlled. If steps (2) and (4) are the ratedetermining steps, the mechanism is particle diffusion controlled (Helfferich, 1962). 

In a separation process, ion exchange resin particles are generally used in a column. A complex time-dependent differential equation for mass balance in the column has to be combined with the diffusion flux expression for a resin particle, and other appropriate boundary and initial conditions, to determine the extent of separation. It is obvious from the preceding few paragraphs that the diffusion flux expressions are difficult to handle for resin particles. For ion exchange column analysis, practical approaches therefore utilize a linear-driving-force representation of the mass flux to a resin particle (Helfferich, 1962 Vermeulen et ai, 1973) this leads to the use of mass-transfer coefficients in resin particle flux expressions. 

Here, is the bulk density of the resin particle and is the outer particle surface area per unit particle volume. The LDF approximation based expressions are provided next Consider the solute concentration profile in any of the two-phase processes considered earlier specifically, select Figure 3.4.2 with the aqueous phase representing the external solution and the organic phase representing the aqueous solution in the pores of the ion exchange resin particle. The rate of transfer of an ionic species A from the bulk solution ( / = w) to the interface between the solution and the resin particle is given by... 

---