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Polysaccharide-based green flocculants: A systematic and comparative study of their coagulation-flocculation
Simon Leonhartsberger1, Pierre Carmona1, Bernhard Seidl2
1Institute of Applied Synthetic Chemistry, TU Wien, Vienna, Austria.
Carbohydrate Polymers
|May 18, 2025
Summary
Eco-friendly cationized polysaccharides show enhanced flocculation efficiency for water treatment. This study introduces a flocculation score and compares six polysaccharides, finding cationic pullulan and starch most effective among modified options.
Area of Science:
- Green Chemistry and Environmental Science
- Polymer Science and Engineering
- Water Treatment Technologies
Background:
- Growing demand for sustainable flocculants to replace synthetic options.
- Limited systematic comparative analyses of cationized polysaccharides for coagulation-flocculation.
- Need for robust evaluation metrics in flocculation studies.
Purpose of the Study:
- To evaluate and compare the coagulation-flocculation efficiency of unmodified and cationized polysaccharides.
- To introduce a novel flocculation score for robust evaluation and comparison.
- To investigate the influence of molecular weight, charge density, and viscosity on flocculation performance.
Main Methods:
- Characterization of six polysaccharides (starch, chitosan, inulin, guar gum, pullulan, hydroxyethyl cellulose) using AsFlFFF-MALS, NMR, PCD, rheology, SEM, image analysis, and zeta potential.
- Assessment of flocculation efficiency in kaolin suspension and industrial starch sludge.
- Comparison with synthetic flocculants like cationic polyacrylamide (cPAM) and Poly(Diallyldimethylammonium Chloride) (pDADMAC).
Main Results:
- Cationized polysaccharides demonstrated significantly enhanced flocculation compared to their unmodified counterparts.
- Higher charge density improved flocculation in kaolin suspensions; higher molecular weight benefited industrial sludge.
- Chitosan was the leading unmodified polysaccharide, while cationic pullulan and starch excelled among modified versions.
Conclusions:
- Cationized polysaccharides offer a promising eco-friendly alternative to synthetic flocculants.
- Flocculation efficiency is influenced by polysaccharide molecular weight and charge density.
- The study provides valuable insights for optimizing water treatment processes using biopolymers.
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