Removal of yttrium (III) ions from water solutions by alginate compounds

The presence of radioactive substances in wastewaters poses a problem for public health due to the lack of the radioisotope-binding materials. In the present study, the yttrium-binding activity of sodium and calcium salts of alginic acid was investigated in a batch sorption system. The results showed that both polymers are able to form complexes with yttrium ions. The effects of contact time, initial concentration of the metal and pH of the media on the yttrium-binding processes were experimentally investigated. The equilibrium time was found to be at least 60 min required for adsorption of yttrium by alginate compounds regardless of the initial metal concentrations. Langmuir and Freundlich sorption models were applied for description of the binding processes. The results showed that the Langmuir model is best fit within the whole range of pH values used in the studies. The maximum adsorption capacity of calcium and sodium alginates was found to be 99.01 and 181.81 mg/g, respectively, at pH 6.0. Kinetic studies showed that reactions between alginate compounds and yttrium are corresponding to the pseudo-second-order model. These results obviously show that alginate salts may be successfully used as materials for elimination of radioisotopes from water disposals.

Keywords
Alginate; Yttrium; Biosorption; Adsorption isotherm; Equilibrium; Kinetics