Adsorbents resins

Polymeric cation-exchange resins are also used in the separation of fmctose from glucose. The UOP Sarex process has employed both 2eohtic and polymeric resin adsorbents for the production of high fmctose com symp (HFCS). The operating characteristics of these two adsorbents are substantially different and have been compared in terms of fundamental characteristics such as capacity, selectivity, and adsorption kinetics (51). 

The 2eohte and the resin adsorbents show different adsorption isotherm characteristics, particularly at higher concentration (51). The resin adsorbent isotherm is slightly concave upward, whereas the 2eohte isotherm is linear, or even slightly concave downward. Resins, therefore, have an advantage in a UOP Sarex operation that involves high feed-soHds concentration. 

Resin adsorbents (macroreticulat polymer resins) generally good for removal of up to 1—2% of stream (often regenerable). 

Base exchange The property of the trading of cations shown by certain in- soluble namrally occurring materials (zeolites) and developed to a high degree of specificity and efficiency in synthetic resin adsorbents. 

Recognizing the need for a more economically and environmentally friendly citric acid recovery process, an adsorptive separation process to recover citric acid from fermentation broth was developed by UOP [9-14] using resin adsorbents. No waste gypsum is generated with the adsorption technique. The citric acid product recovered from the Sorbex pilot plant either met or exceeded all specifications, including that for readily carbonizable substances. An analysis of the citric acid product generated from a commercially prepared fermentation broth is shown in Table 6.2, along with typical production specifications. The example sited here is not related to zeolite separation. It is intent to demonstrate the impact of adsorption to other separation processes. 

Kulprathipanja, S., Oroskar, A.R., and Priegnitz, J.W. (1989) Separahon of citric add from fermentahon broth with a weakly basic anionic exchange resin adsorbent. U.S. Patent 4,851,573. 

The ratio of the distribution coefficients of pertechnetate and perrhenate is about 1.6 to 2, comparable to adjacent rare earth metals. Technetium and rhenium may be separated by ion-exchange chromatography. However, efficient separations require some care and tend to be slow. On the other hand, cation exchange resins adsorb technetiiun only to a negligible extent so that pertechnetate can be rapidly separated from cationic elements . 

XAD-2 and XAD-4 macroreticular resin adsorbents were found to be adequate to accumulate the organic pollutants considered in the present study except for bis(2-ethylhexyl) phthalate. Polyurethane-carbon ad-... 

Figure 19.12. Batch parametric processing of solid-liquid interactions such as adsorption or ion exchange. The bottom reservoir and the bed interstices are filled with the initial concentration before pumping is started, (a) Arrangement of adsorbent bed and upper and lower reservoirs for batch separation, (b) Synchronization of temperature levels and directions of flow (positive upward), (c) Experimental separation of a toluene and n-hcptane liquid mixture with silica gel adsorbent using a batch parametric pump. (Reprinted from Wilhelm, 1968, with permission of the American Chemical Society), (d) Effect of cycle time t on reservoir concentrations of a closed system for an NaCl-H20 solution with an ion retardation resin adsorbent. The column is initially at equilibrium with 0.05M NaCl at 25°C and a = 0.8. The system operates at 5° and 55°C. [Sweed and Gregory, AIChE J. 17, 171 (1971)J.

Fig. 1. Schematic flowsheet of uranium processing (acid leach and ion exchange) operation. Numbers refer to the numbers that appear in the boxes on the flowsheet. Operations (3), (6), (9), and (11) may be done by thickening or filtration. Most often, thickeners are used, followed by filters. The pH of the leach slurry <4) is elevated to reduce its corrosive effect and to improve the ion-exchange operation on the uranium liquor subsequently separated, In tile ion exchange operation (7), resin contained in closed columns is alternately loaded with uranium and then eluted. The resin adsorbs the complex anions, such as UC fSO 4-. in which the uranium is present in the leach solution. Ammonium nitrate is nsed for elution, obtained by recycling the uranium filtrate liquor after pH adjustment. Iron adsoibed with the uranium is eluted with it. Iron separation operation (8) is needed inasmuch as the iron hydroxide slurry is heavily contaminated with calcium sulfate and coprecipitated uranium salts. Therefore, the slurry is recycled to the watering stage (3). Washed solids from 1,6). the waste barren liquor from (7), and the uranium filtrate from (11) are combined. The pH is elevated to 7.5 by adding lime slurry before the mixture is pumped to the tailings disposal area. (Rio Algom Mines Limited, Toronto)...

In an alternative process, frozen cells of S. paucimobilis SC 16113 were used with resin adsorbed (XAD-16 resin) substrate at 5- and 10-g/liter substrate concentrations. In this process, an average reaction yield of 85% and an e.e. of >99% were obtained for product (7). At the end of the biotransformation, the reaction mixture was filtered on a 100-mesh (150-m) stainless steel screen, and the resin retained by the screen was washed with 2 liters of water. The product was then desorbed from the resin and crystallized in an overall 75 M% yield with 91% homogeneity and 99.8% e.e. 

Although the resins adsorbed levulinic, acetic, as well as formic acid, formic acid was released later than acetic and levulinic acid, which typically were eluted similarly. This can be explained by the fact that the pKa of formic acid (3.75) is considerably lower than that of acetic (4.74) and levulinic (4.5) acid. The initial concentrations of levulinic, acetic, and formic acid in untreated hydrolysate were 12,53, and 24 mM, respectively. The total concentration of the three aliphatic acids, 89 mM, is relatively modest considering that previous results indicate that concentrations below 100 mM lead to an increase rather than a decrease in the ethanol yield (11). The effect of the acids is pH dependent, and under anaerobic conditions, the concentration of the undissociated form of acetic acid in the medium should not exceed 5 g/L (80 mM) for growth to occur (29). The low concentration... 

A more selective recovery of nickel from plating wastewater was described by Eom et al. [103].They used a column packed with strongly acidic cation resin through which over 99% nickel ion was removed. In this process, sulfuric acid was employed with a reagent in order to regenerate nickel ions from the resin adsorbed. Moreover, the nickel ions recovered by sulfuric acid were obtainable up to 120 g-Ni L 1 allowing reuse in the plating bath. 

Thus, Kd (uranium) for B-4 is 19900 meq/g and for L-4 it is only 810 meq/g. In general, the IV-methylated resins adsorb more U02 + and less Cu2+ ions than the unmethylated resins. This may be due to the presence of tertiary amino and ammonium groups which are assumed to favor the adduct formation with... 

The resin adsorbs Cu(II), Cd(II) and Hg(II) and shows a selectivity depending on the pH. The thiol groups are stable towards oxidation in the atmosphere for two months. 

On a positive note, the sticky nature of a-factor can also be used to facilitate its purification and concentration. Amberlite X AD resin adsorbs hydrophobic molecules and can effectively capture a-factor from the yeast culture supernatant [18,91]. Elution from this resin can be accomphshed with methanol or... 

Results of adsorption experiments are presented in Table 2. In solution, TNF-a, a polypeptide with MW 17 kD, exists as a trimer with MW 51 kD. The monomeric units are kept together due to the hydrophobic interaction. From the experimental data it is clear that large mesopores play a relatively minor role in adsorption of TNF-a, as both MN resins adsorb it rather efficiently. Isoelectric point of TNFa is similar to that of serum albumin (pi between 4.8 and 5.6) [11], It has been shown that TNFa can be removed from biological media using non-polar cross-linked polystyrene adsorbents of the Amberlite type (XAD-2, XAD-4 and XAD-6) [12], This observation confirms that hydrophobic interactions play an important role in the adsorption of TNFa at neutral pH. Our data support this conclusion. 

In this study, the solvent recovery by PSA with resin adsorbent and high silica zeolite was tested. As a first step, CH2CI2 was chosen as solvent and the following items were examined. 

The product gas and the exhaust gas were measured for dichloromethane-laden air feed by PSA system using a resin adsorbent and a high silica zeolite as adsorbent. The PSA method for solvent recovery with each adsorbent seems to be technically feasible. The high silica zeolite gave better performance than the resin adsorbent, as expected from their isotherms. 

Fig. 1 Comparison between Microwave and Thermal Regeneration of NKA-II Resin. Adsorbate Benzene, N2 Flow Rate 0.16 m /h...

The first example for Method 2 was reported by Nishide and co-workers, who polymerised a metal complex of 1-vinylimidazole with l-vinyl-2-pyrollidone and divinylbenzene [8]. The metal-vinylimidazole complex was copolymerised, cross-linked with l-vinyl-2-pyrollidone by y-ray irradiation and the template metal ion was removed by treating the polymer complex with an acid. These poly(vinyl-imidazole) (PVI) resins adsorbed metal ions more effectively than the PVI resin prepared without the template. The number of adsorption sites and the stability constant of the Ni(II) complex were larger for the PVI resin prepared with the Ni(II) template, as seen by the smaller dissociation rate constant of Ni(II) from the resin. 

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