Synthesis and characterization of modified lignin flocculants for Congo red and methylene blue removal

Authors

  • Mr. Mark Xavier Bailon Department of Science and Technology, Philippine Science High School – Central Luzon Campus and Department of Environmental Science, School of Science and Engineering, Ateneo de Manila University Author https://orcid.org/0000-0001-7900-1695
  • Bianca Marie Lim Department of Science and Technology, Philippine Science High School – Central Luzon Campus and College of Medicine, University of the Philippines – Manila Author https://orcid.org/0009-0000-3484-8737
  • Gian Margarette Villadarez Department of Science and Technology, Philippine Science High School – Central Luzon Campus and Department of Physics, School of Science and Engineering, Ateneo de Manila University Author https://orcid.org/0009-0005-2759-3736

DOI:

https://doi.org/10.46488/

Keywords:

dye removal, grafted flocculant, METAC, sulfonic acid

Abstract

This study aimed to synthesize lignin-based flocculants by grafting sulfonic acid (SA) and [2-(methacryloyloxy) ethyl] trimethylammonium chloride (METAC) using potassium persulfate as initiator. The flocculants were characterized for particle size, thermal stability, surface morphology, and functional group analysis. Their dye removal performance was tested against Congo red and methylene blue at different pH levels. FTIR analysis confirmed successful grafting of METAC and SA groups on the lignin backbone for the lignin-METAC, lignin-SA, and lignin-METAC-SA. Particle size analysis showed an increase in particle size only with the Lignin-METAC-SA. Lignin modification leads to increased folding and the presence of raised structures in the modified flocculants. Compared to unmodified lignin (384°C), maximum thermal degradation occurs at relatively higher temperatures (400-500°C) for all modified lignin flocculants. Lignin modification enhanced the dye removal performance of the flocculant, with lignin-SA showing the highest removal efficiencies for both dyes. All lignin-based flocculants performed better against methylene blue at all pH levels, with lignin-SA (82.9%) and lignin-METAC-SA (82.3%) achieving the highest reduction efficiencies at pH 10. Higher removal efficiency (46-69%) was observed for Congo red in more acidic solutions (pH 4) for all lignin flocculants. These results highlight the potential of grafted lignin-based flocculants for dye wastewater treatment.

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September 2026 (Forthcoming Issue)

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Articles