Biomass-Derived Flocculants for Wastewater Treatment

The selective extraction and recovery of different molecules of interest from lignocellulosic materials from forestry residues are increasing every day, driving society towards more sustainable approaches and materials. For this purpose, the development of new sustainable and ecologically benign extraction methodologies has grown significantly. Deep eutectic solvents (DESs) appear as a promising alternative for the processing of biomass [1, 2]. In the present study, cellulose-rich fractions obtained from the fractionation of Acacia wood, an invasive species in Portugal, were used to prepare cationic and hydrophobically modified cationic bioflocculants used for wastewater treatment with a focus on microplastics removal [3].

On the other hand, Eucalyptus bleached pulp was also used to prepare anionic and cationic bioflocculants used to treat effluents from the textile industry [4]. The bioflocculant preparation route follows a two-step process, with the introduction of reactive aldehyde groups in the cellulose molecules, followed by cationization or anionization. The hydrophobic variation was obtained by a third step, by esterification of the C₆ OH groups of cellulose with fatty acids obtained from vegetable oils.

All the obtained bioflocculants revealed high performance, according to the results obtained in Laser Diffraction Spectroscopy, at the same level as or even superior to synthetic alternatives, cationic and anionic polyacrylamides, with lower environmental impact.

1. Magalhães, S., et al., Enhancing Cellulose and Lignin Fractionation from Acacia Wood: Optimized Parameters Using a Deep Eutectic Solvent System and Solvent Recovery. Molecules, 2024. 29(15): p. 3495.
2. Magalhães, S., et al., Acacia Wood Fractionation Using Deep Eutectic Solvents: Extraction, Recovery, and Characterization of the Different Fractions. ACS Omega, 2022. 7(30): p. 26005-26014.
3. Magalhães, S., et al., Tailored cellulose-based flocculants for microplastics removal: Mechanistic insights, pH influence, and efficiency optimization. Powder Technology, 2025. 456: p. 120838.
4. Grenda, K., et al., Environmentally friendly cellulose-based polyelectrolytes in wastewater treatment. Water Science and Technology, 2017. 76(6): p. 1490-1499.