Molecular engineering for synthesizing flocculation /extraction bifunctional polymer and one-way liquid–liquid mass transfer at oil/water interfaces

The production of high-quality reclaimed water is a highly desirable goal in wastewater treatment. Rational design of bifunctional polymer with both superior flocculation and extraction performance was achieved according to the molecular engineering strategy. Leveraging its bifunctional nature, a flocculation/extraction coupled process was constructed for reducing residual polymer content in reused water. Color removal of about 99.0 % is achieved while maintaining low residual polymer content (less than 3.0 %) by a combination of flocculation with extraction process. The self-cleaning mechanism of the polymer relies on one-way liquid–liquid mass transfer at oil/water interfaces. The polymers preferentially partition into the oil phase when extraction acts as post-treatment control due to the increased partition coefficient at the oil/water interface. Importantly, the intermolecular hydrophobic interaction among bifunctional polymer plays an important role in inhibiting the retro-diffusion of extract-phase polymers to the raffinate phase, resulting in minimal residual polymer concentration in the recycled water. The wastewater with high salinity (60 g/L) can be directly recycled and reused for three-times as new dyeing baths, minimizing the environmental impact of reactive dyeing systems. A new resourcezation strategy of wastewater has been proposed to address challenges of self-cleaning residual wastewater treatment agents by bifunctional polymer.