Selective Sorption of Heavy Metals by Renewable Polysaccharides

Area of Science:

• Materials Science
• Environmental Chemistry
• Biopolymers

Background:

• Renewable polysaccharides are valuable for heavy metal ion sorption due to acidic functional groups.
• Alginate, iota-carrageenan, and lambda-carrageenan possess carboxylic and sulfate ester groups, enhancing their adsorption capabilities.

Purpose of the Study:

• To evaluate the efficacy of alginate and carrageenans in recovering heavy metal ions from aqueous solutions.
• To compare the sorption performance and selectivity of these polysaccharides, individually and in mixtures.

Main Methods:

• Utilized alginate, iota-carrageenan, and lambda-carrageenan as sorbents for heavy metal ions (Eu³⁺, Sm³⁺, Er³⁺, UO₂²⁺).
• Employed X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and Fourier-transform infrared spectroscopy (FTIR) for material characterization and confirmation of adsorption.

Main Results:

• All tested polysaccharides successfully adsorbed tested heavy metal ions.
• Alginate demonstrated the highest sorption yields for all metal ions, whether used alone or in mixtures.
• Carrageenans exhibited greater selectivity for lanthanides (e.g., Eu³⁺, Sm³⁺, Er³⁺) compared to uranyl ions (UO₂²⁺).

Conclusions:

• Alginate is a highly effective biosorbent for heavy metal removal.
• The functional groups (carboxylic vs. sulfate ester) on polysaccharides dictate their adsorption selectivity.
• Polysaccharide-based sorbents offer a promising route for heavy metal remediation from contaminated water sources.