Adsorptive Activity of Cation-exchange Resins for Urea in Aqueous Solutions

FUJITA Yoshie, OKAZAKI Susumu

doi:10.1246/nikkashi.1987.1530

In order to find out an effective adsorbent for removal of urea in blood, the urea adsorption properties of metal oxides, activated carbons, oxidized starch, and ion-exchange resins were examined in aqueous solution. Cation-exchange resins having sulfonic acid groups indicated the highest adsorptive activity for urea (Table 1). Besides commercially available strong acid cation exchangers such as Amberlite IR-120 B and Amberlyst 15, sulfonated p-vinylphenol-divinylbenzene copolymers carrying SO₃H groups exhibited a relatively high adsorptive capacity. For these resins, the amount of adsorbed urea was directly proportional to the ion-exchange capacity (Fig.2). Thus, the sulfonic acid group of the resin might participate in the urea adsorption. The adsorption of urea on Amberly st 15 was found to be of the Langmuir type (Fig.4). The amount of saturated adsorption of urea estimated from the Langmuir equation was close to the value of the ion-exchange capacity of the resin. The apparent heat of urea adsorption on Amberlyst 15 was estimated to be 12.5 kJ.mol^-1 at initial urea concentration of 35.7 mmol.l^-1 and at temperatures from 20 to 50°C. The FT-IR absorptiom spectra (Fig.6) suggested that urea molecules are attached to the ion exchangers through the bond between hydrogen atom of the sulfonic acid group of resin and the nitrogen atom of the urea molecule. Since the hydrogen bond thus formed is weak, the urea adsorption takes place reversibly.

Adsorptive Activity of Cation-exchange Resins for Urea in Aqueous Solutions

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