Page 55 - חוברת תזות הנדסה ירוקה 2023

Removal of Europium from aqueous solutions by renewable polysaccharides
Chanan Yanay1; chanannn@gmail.com
Prof. Adi Wolfson1, Dr. Oshrat Levy-Ontman1, Dr. Ofra Paz-Tal2 1Sami Shamoon College of Engineering
2Nuclear Research Center Negev
During the last decades, the amounts of industrial wastewater, including those containing heavy and radioactive metals, have been increasing. These wastewaters cause land, water, and air pollution, and pose a severe environmental problem. Polysaccharides produced from biological sources are renewable, biodegradable and usually hydrophilic polymers, known to be safe for use. Each polysaccharide has its own characteristics, depending on its functional groups and its structure. These properties, among other things, also allow them to be used very successfully as adsorbents for heavy metal ions. In this study, polysaccharides from a variety of biological sources were used for the adsorption of europium ions )Eu3+, derived from europium chloride or europium nitrate( from aqueous solutions. The tested polysaccharides are: iota )I(, alginate )A(, xanthan )X(, guar gum )G(, kappa )K(, lambda ) (, and a polysaccharide extracted from red algae Porphyridium sp. )P(. All the polysaccharides adsorbed the Eu3+ ions, and the adsorption yields varied across a large range. It was concluded that the amount and the acidic strength of the functional groups in the polysaccharides dictate their adsorption yields. Decreasing the concentration of the metal in the solution or increasing the amount of the polysaccharide, increased the sorption yields. Changing the pH of the solution affected the yields, that were usually higher at higher pH values )up to pH=7(. However, under basic conditions, above pH=7, precipitates of the metal ions were formed. The addition of different salts to the Eu3+ ion solution: NaCl, CaCl2·2H2O, and MgCl2·6H2O, in different amounts, caused a decrease in the sorption yield of the Eu3+ ions. In addition, it was found that the valence level of the ion also affected the adsorption, so the presence of Na+ resulted in the smallest decrease in the sorption yield compared to an addition of Ca2+ ions and Mg2+. Finally, kinetics experiments determined that pseudo-second order is the most suitable for the adsorption of Eu3+ ions on I. Changing the polysaccharide concentration from 1 w/v% to 2 w/v% caused a decrease in adsorption utilization but led to the creation of more stable hydrogels that are easier to separate. Using Eu)NO3(3·6H2O or EuCl3·6H2O resulted in similar sorption yields. Then, I and A were also used to adsorb samarium ions )Sm3+(, and no significant change was observed between the sorption yield of Eu3+ and Sm3+. Moreover, it was found that this adsorption is not selective, and adsorption from a mixture of the two metal ions is similar to the adsorption of ions of each metal separately. In the last stage of this study, the
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