Preparation of alginate fibers coagulated by calcium chloride or sulfuric acid: Application to the adsorption of Sr2

Abstract

The adsorption behavior of Sr²⁺ over alginate (Alg) fibers prepared by wet spinning was investigated. Different grades of sodium alginate (Alg-Na) were chosen. The Alg fibers were obtained by coagulation of 1% H₂SO₄ (Alg-acid) or 5% CaCl₂ (Alg-Ca) solutions. In addition, the Sr²⁺ adsorption percentages of the spherical Alg-Ca beads with a 0.672-mm-diameter was 70.64% which was significantly lower than that Alg-Ca fibers (79.49%). These results suggested that the fibrous shape is more suitable than the spheres as an adsorbent from sea water. For Sr²⁺ adsorption capacities using different Alg fibers, the Alg-acid fibers obtained from 12% IL-2 and 8% I-2 grade solutions reached adsorption equilibrium at 99.88 and 99.27%, respectively, within 3 min. However, the Alg-Ca fiber obtained from 8% I-2 grade solution reached equilibrium at 80.01% within 30 min. Moreover, the Alg-acid fiber obtained from 8% I-2 grade solution adsorbed up to 34 mg/g of Sr²⁺ at an initial concentration of 1700 mg/L solutions. However, when Sr²⁺ co-existing cations (Ca²⁺, Na⁺, and mixtures of them) the adsorption capacity of the Alg-Ca fiber obtained from 8% I-2 grade solution slightly decreased since the egg-box structure of Alg-Ca fiber favored the selective Sr²⁺ adsorption and subsequent ion exchange with Ca²⁺.

Keywords: Absorption; Alginate fiber; Strontium.