Structural and Sorption Characteristics of Nano-Structured Polysaccharide Biopolymers Derived from Plants of the Asteraceae Family

Abstract

This study investigates the structural and sorption characteristics of nanostructured polysaccharide biopolymers isolated from plants of the Asteraceae family (Dahlia tubers and Helianthus tuberosus) toward Pb²⁺ ions in model aqueous solutions. The biopolymers were obtained by acid extraction at pH 1.5-2.5 and 80-90 °C, followed by ethanol precipitation, with a yield of 10-14%.
Surface morphology examined by scanning electron microscopy revealed a hierarchically organized nano- and micro structured matrix with particle agglomeration and developed interaggregate porosity. The presence of lamellar structures and a porous network promotes diffusion of metal ions to active functional centers.
The interaction mechanism between the biopolymer matrix and Pb²⁺ was studied by FTIR spectroscopy. Shifts and intensity changes of absorption bands corresponding to carboxyl and hydroxyl groups confirmed a coordination-chelate complexation mechanism without destruction of the polysaccharide backbone.
Sorption experiments were performed using model Pb²⁺ solutions prepared from analytical-grade lead (II) acetate. The residual Pb²⁺ concentration after contact with the biopolymer was determined by atomic absorption spectrometry at 283.3 nm using calibration. Additional control measurements were conducted by complexometric titration in acetate buffer medium (pH 5.5) with 0.01 M Trilon B.
Up to 76-77% of Pb²⁺ was removed within the first 10 min, and sorption equilibrium was reached after 60 min. The maximum removal efficiency reached 87%. The Freundlich model best described the process, indicating heterogeneous surface structure and multilayer adsorption. These results demonstrate the potential of Asteraceae-derived polysaccharide biopolymers as environmentally safe sorbents for heavy metal removal from aqueous media.