Adsorpcija uranijum(VI)-jona na modifikovanom hejlanditsko/klinoptilolitskom zeolitskom tufu

Abstract

U radu je ispitivana adsorpcija uranijum(VI)-jona na površinski modifikovanom hejlanditsko/klinoptilolitskom zeolitskom tufu (organozeolitu). Organozeoliti su dobijeni jonskom izmenom neorganskih katjona sa površine zeolita sa heksadecil trimetil amonijum (HDTMA) jonima. Dobijeni rezultati su pokazali da je adsorpcija uranijum(VI)-jona na nemodifikovanom zeolitskom tufu niska (indeks adsorpcije 35% odnosno 0,34 mg uranijum(VI)-jona/g adsorbenta), dok kod organozeolita, adsorpcija uranijum(VI)-jona raste sa porastom sadržaja HDTMA na površini hejlandita/klinoptilolita. Najviši indeksi adsorpcije su dobijeni na organozeolitu od kojeg su svi katjoni sa spoljašnje površine zamenjeni sa HDTMA(OA.-10). Ispitivanja adsorpcije uranijum(VI)-jona na organozeolitu OA-10, na različitim pH su pokazala da adsorpcija raste sa porastom sadržaja adsorbenta u suspenziji. Kako oblik uranijum(VI)-jona u rastvoru, zavisi od pH sredine, isti oblik adsorpcionih izotermi na pH 6 i 8 (Langmuir-ov tip izoterme), ukazuje da se uranijum(VI)-jon u istom obliku apsorbuje na površini zeolitskog tufa. Adsorpcija uranijum(VI)-jona pri pH 3 odgovara Tipu III adsorpcione izoterme.

The adsorption of uranium(VI) on heulandite/clinoptilolite rich zeolitic tuff modified with different amounts (2, 5 and 10 meq/100 g) of hexadecyltrimethyl ammonium (HDTMA) ion was investigated. The organozeolites were prepared by ion exchange of inorganic cations at the zeolite surface with HDTMA ions, and the three prepared samples were denoted as OA-2, OA-5 and OA-10. The maximal amount of HDTMAin the organozeolite OA-10 (10 meq/100 g) was equal to the external cation exchange capacity of the starting material. The results showed that uranium( VI) adsorption on unmodified zeolitic tuff was low (0.34 mg uranium(VI)/g adsorbent), while for the organozeolites, the adsorption increased with increasing amount of HDTMA at the zeolitic surface. The highest adsorption indexes were achieved for the organozeolite OA-10, in which all the surface inorganic cations had been replaced with HDTMA. An investigation of the adsorption of uranium(VI) ions onto organozeolite OA-10 at different pH values (3, 6 and 8) showed that the adsorption index increased with increasing amount of adsorbent in the suspension. Since uranium(VI) speciation is highly dependent on pH, from the adsorption isotherms, it can be seen that uranium(VI) adsorption on organozeolite OA-10 at pH 6 and 8 is well described by a Langmuir type of isotherm, while at pH 3, it corresponds to a Type III isotherm.