(453e) Calcium Alginate Thin Films Derived from Sargassum Natans for the Selective Adsorption of Cd2+, Cu2+, and Pb2+ Ions

Calcium alginate is biopolymer, well known for its ion exchange characteristics and has often been exploited for heavy metal sequestration using spherical beads with high surface area per unit volumes. Thin-films, however, also have large surfaces for mass transfer due to their effective thicknesses (<100 µm) and thus allow for enhanced mass transfer properties. Furthermore, calcium alginate thin films have not been utilized or fabricated for heavy metal sorption, and thus presents the novel contribution in this research. Hence, this study aims to investigate the adsorption capacities of Pb²⁺, Cu²⁺ and Cd²⁺ions for calcium alginate thin films. Adsorption characteristics was investigated using Sigma-Aldrich, Protanal, Manugel and sodium alginate extracted from native Sargassum Natans. The Langmuir isotherm successfully modeled the adsorption phenomena of Pb²⁺ and Cu²⁺ with a maximum monolayer adsorption capacities of 4701 to 8475 mg/L for Pb²⁺ and 4292 to 6494 mg/L for Cu²⁺. While the Freundlich isotherm indicated that Cd²⁺ binds heterogeneously with the alginate surface. Furthermore, it was found that process was predominantly governed by ion exchange whereby bidentate chelating coordination resulted in the respective ion binding affinity. Kinetic studies into adsorption behavior showed that the heavy metals followed the pseudo-second-order model with a maximum adsorption capacity of 1819 to 4489 mg/L for Pb²⁺, 1805 to 3136 mg/L for Cu²⁺ and 1556 to 1781 mg/L for Cd²⁺. Also, NMR characterization revealed that an increase in G-block monomer units followed an increase in adsorption capacity and kinetic rate constant. Insights into, the selectivity of the different ions revealed that the metal affinity for calcium alginate was as follows, Pb²⁺ > Cu²⁺ > Cd²⁺. The results of this study successfully shows the potential of calcium alginate thin-films as effective adsorbents for heavy metal ions.