Valorization of orange peel pectin for efficient polyethylene microplastic removal: A circular bio-flocculation process

Microplastics (MPs) have emerged as pervasive pollutants posing significant risks to ecosystems and human health. Current removal strategies, such as filtration, coagulation, and biological degradation, are limited by material specificity, operational costs, and incomplete capture of smaller MPs. This study presents an innovative bio-flocculation approach employing pectin extracted from orange peel to enhance the removal of polyethylene (PE) MPs (0.5–125 µm) through synergistic interactions with Fe³⁺ ions. Response surface methodology (RSM) and ANOVA confirmed the goodness of fitting of the developed quadratic model (F = 109.21, p < 0.0001, R² = 0.94), with pectin dosage identified as the most influential parameter (F = 130.17, p < 0.0001). The process exhibited strong quadratic dependence on both dosage and pH, indicating an optimal pH near neutrality and diminishing returns at higher dosages. Under optimized conditions (pectin = 25–30 mg, pH ≈ 7, time ≈ 90 min), the removal efficiency ranged from 94.0–96.1 ± 0.6%. The results demonstrate that pectin effectively bridges MPs and Fe³⁺ via electrostatic and hydrogen-bonding interactions, enabling rapid, energy-efficient aggregation. The use of pectin from oranges could provide a scalable, low-carbon solution for mitigating MP pollution, valorize agricultural waste streams, and contribute directly to the United Nations Sustainable Development Goals (SDGs) through the advancement of circular and green chemistry practices.