부산대학교 도서관

The sorption of [Cd.sup.2+] from natural seawater, artificial seawater, distilled water and NaCl solution of the same ionic strength as the seawater onto zeolite modified by iron(III) oxide (Fe(III)-zeolite) was investigated. The sorption was found to be time, concentration and pH dependent. The sorption capacity at the initial pH 7 decreased in the following order: distilled water > NaCl solution > artificial seawater > natural seawater. The isotherm study showed that Langmuir isotherm model could be adequately applied for the sorption in distilled water, indicating the homogeneous monolayer coverage at Fe(III)-zeolite surface, while the Freundlich isotherm model showed a better fit than the Langmuir model of the sorption data in saline waters, indicating multilayer heterogeneous coverage at the sorbent surface. The values of Freundlich parameter n suggested that the sorption was a favorable process and bonds between [Cd.sup.2+] and Fe(III)-zeolite surface were stronger in NaCl solution than in natural and artificial seawater. Kinetics analysis showed that the mechanism of [Cd.sup.2+] sorption from natural seawater differed from the sorption mechanism out of distilled water, NaCl solution and artificial seawater. The intra-particle diffusion kinetic model indicated that both boundary layer diffusion and intra-particle diffusion influenced the rate of sorption. Keywords: sorption, cadmium ions, Fe(III)-zeolite, seawater, modeling. U ovom radu je ispitivana sorpcija [Cd.sup.2+] iz prirodne morske vode, laboratorijski pripremljene morske vode, destilovane vode i rastvora NaCl, iste jonske jacine kao morska voda, na zeolitu modifikovanom gvozde(III)-oksidom. Pokazano je da sorpcija zavisi od vremena, pocetne koncentracije [Cd.sup.2+] i pH vrednosti. Sorpcioni kapacitet Fe(III)-zeolita za [Cd.sup.2+] pri pocetnoj pH 7 opada u sledecem nizu: destilovana voda > NaCl rastvor > laboratorijski pripremljena morska voda > prirodna morska voda. Modelovanje rezultata ispitivanja sorpcije u ravnoteznim uslovima je pokazalo da se adsorpcija iz destilovane vode moze opisati Langmirovim modelom, sto ukazuje na homogenu sorpciju i formiranje monosloja na povrsini Fe(III)-zeolita. Rezultati sorpcije iz slanih voda se bolje opisuju Frojndlihovim nego Langmirovim modelom, sto ukazuje na viseslojnu sorpciju na heterogenoj povrsini sorbenta. Vrednosti Frojndlihovog parametra n pokazuju da je sorpcija [Cd.sup.2+] na Fe(III)-zeolitu favorizovan proces i da su veze izmedu [Cd.sup.2+] i povrsine Fe(III)-zeolita jace u NaCl rastvoru nego u prirodnoj i laboratorijski pripremljenoj morskoj vodi. Kineticka analiza sorpcije je pokazala da se mehanizam sorpcije iz prirodne morske vode razlikuje od mehanizma sorpcije iz ostalih ispitivanih tipova vode. Kineticki model unutarcesticne difuzije je pokazao da i difuzija kroz granicni sloj i unutarcesticna difuzija odreduju brzinu sorpcije. Difuzija kroz granicni sloj je u vecoj meri zastupljena kod sorpcije iz morske vode nego u slucaju sorpcije iz drugih ispitivanih tipova vode. Kljucne reci: Sorpcija * Kadmijum jon * Fe(III)-zeolit * Morska voda * Modelo-vanje Available online at the Journal website: http://www.ache.org.rs/HI/
Cadmium is one of the most toxic heavy metals. It tends to accumulate in the body and it has varying degrees of toxicity. Cadmium causes serious diseases such as renal [...]