Work

Integrated Chitosan-based coagulation and microbubble pre-treatment for improved microplastic fibre removal from water

Year: 2025

Type: article

Abstract: Microplastic fibres (MPFs) dominate treatment plant influents but are difficult to remove due to their morphology, composition and low density, limiting the effectiveness of coagulation flocculation pre-treatment. Integrating coagulation-flocculation with microbubble introduction offers a sustainable route to improve MPF removal, yet conventional inorganic coagulants often require high dosages, show strong pH dependence, and pose environmental risks. Chitosan is a biodegradable and non-toxic green alternative, but its application is limited due to its low solubility and pH sensitivity. In this study, two amphoteric derivatives of Chitosan have been successfully developed: CMC-CTA, produced by modifying carboxymethyl Chitosan (CMC) with 3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CTA); and CMC-g-PDMC, obtained by grafting poly[(2-methacryloyloxyethyl) trimethyl ammonium chloride] (PDMC) onto the CMC backbone. MPF removal was evaluated in a deionised (DI) water matrix containing sodium dodecyl benzene sulphonate (SDBS) surfactant using a tailored turbidity measurement approach. To broaden the investigation, additional matrices were explored, including humic acid (HA) alone and HA combined with MPF (HA + MPF) at varying HA concentrations. In the DI water + SDBS matrix, the highest MPF removal was achieved using 1 mg/L CMC-CTA at pH 7. Zeta potential measurements indicated that charge patching occurred during the coagulation process, where microbubble attachment to MPF flocs appeared to facilitate the removal mechanism. The same system was also effective in reducing over 50% of the turbidity caused by 20 mg/L HA in both the HA-only and HA + MPF matrices. The outcomes provide great insights into the hybrid pre-treatment approaches targeting MPFs' removal. • First demonstration of coagulation-flocculation-microbubble introduction hybrid system for MPF removal • CMC-CTA outperformed Chitosan and CMC-g-PDMC at neutral pH and 1 mg/L dose • Simultaneous MPF-Humic acid turbidity removal was achieved at low coagulant dosage. • Zeta potential confirmed synergistic charge neutralisation, charge patching and microbubble attachment.

Source: The Science of The Total Environment

DOI: 10.1016/j.scitotenv.2025.181039

Authors: Nimesha Thathsarani, Mohadeseh Najafi, Mehdi Khiadani, Muhammad Rizwan Azhar, Masoumeh Zargar

Institution: Edith Cowan University

Language: English

Topic: Microplastics and Plastic Pollution

Subfield: Pollution

Field: Environmental Science

Domain: Physical Sciences

SDGs: Clean water and sanitation, Responsible consumption and production

Open Access status: hybrid

Estimated APC paid: $4,250