Normal-sized beads

Normal-Sized Beads Incorporating Short Diffusion Paths.100... 

Bolto et al. > have constructed normal-sized beads by including both the required types of groups within one particle so that the diffusion paths for proton transfer are much shorter. Amphoteric resins and snake-cage resins can be considered for use as thermally regenerable resins for the reason stated above, however, their practical disadvantage is their lower performance due to the interaction between carboxyl and amino groups which are in very close proximity to one another. 

The rates of salt uptake by mixed-bed normal-bead resins, mixed-bed microtesins, and snake-cage resins are compared in Fig. 7. The rate for tire original mixed bed of normal-sized resins is the slowest. A slight but inadequate improvement occurs if a macroporous amine resin is used instead of a gel-type resin. Rapid rates have been achieved for the mixed-bed microresins of size 10-20 pm and the snake-cage resin of normal bead size comprising a linear poly(acryhc acid) within a macroporous amine... 

In other sulfur recovery operations, better control of product particle size is obtained. The molten sulfur is chilled on a steel belt to produce a roughly 0.5-in.-thick flake sulfur, or sprayed into water or even tumbled in drums to obtain granulated sulfur. Pelletized sulfur, similar in particle size range to the granulated variety, is also obtained when a melt is sprayed into the top of a tower to form droplets of molten sulfur which harden into shot-sized beads as they fall through a current of air. In this form, it is referred to as prills [20]. The narrow size range of particles of prilled sulfur, as well as the negligible dust content in this form, makes it more convenient to use. It normally commands a price premium. 

Physical and chemical structure of resins. The basic material requirements for ion-exchange beads are insolubility, bead size, and resistance to fracture. The resin must be insoluble under normal operating conditions. The beads must be in the form of spheres of uniform dimension normal size range is between 16 and 50 U.S. Mesh. The swelling and contraction of the resin bead during exhaustion and regeneration must not cause the beads to burst. Also, an important property of ion-exchange resins is that the active site is permanently... 

Figure 1. Schematic diagram showing a TRU-spec extraction chromatography method for separation of uranium, thorium, protactinium, and radium from a single rock aliquot. Further purification for each element is normally necessary for mass spectrometric analysis. Analysis of a single aliquot reduces sample size requirements and facilitates evaluation of uranium-series dating concordance for volcanic rocks and carbonates. For TIMS work where ionization is negatively influenced by the presence of residual extractant, inert beads are used to help remove dissolved extractant from the eluant.

The kinetics of the reaction of solid sodium iodide with 1-bromooctane were studied with a 95 % RS graft of polyethylene oxide) 6-mer methyl ether on 3 % CL polystyrene as catalyst (51)176). The rates were approximately first order in 1-bromooctane and independent of the amount of excess sodium iodide. The rates varied with the amount of the solid catalyst used, but there was not enough data to establish the exact functional dependence. All experiments employed powdered sodium iodide, magnetic stirring, and 75-150 pm catalyst beads. Thus the variables stirring speed and particle size, which normally are affected by mass transfer and intraparticle diffusion, were not studied. Yanagida 177) favors a mechanism of transfer of the sodium iodide by dissolution in the solvent (benzene) and diffusion to the catalyst particle... 

Dispersed Powders. The principal use of dispersed powders is in pad—dry—chemical pad—steam dyeing techniques. They are normally made from press cake by ball or bead milling to microparticle size in the presence of dispersing agents. The drying is stricdy controlled and is carried out in the presence of anticoagulants to prevent aggregation of the dispersed dye particles. 

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