The construction of flocculation-to-extraction coupled system with a novel dual-functional polymer for dye wastewater treatment and reuse

The construction of novel materials with multiple functions for water treatment has received wide attention in the field of environmental science. Herein, a dual-functional polymer (DFP) was prepared through the etherification reaction of starch with isopropyl glycidyl ether and 2-chloro-4-dimethylamine-6-diethylamine-[1,3,5]-triazine. DFP exhibited controlled thermo-irreversible on/off properties, and the changes in water solubility could be observed in response to slight stimuli from the external environment. This made DFP a promising candidate for the treatment of dye wastewater through flocculation or extraction. The results showed that the maximum dye uptake capacity and the decoloration efficiency reached 976 mg/g and 97.2 %, respectively, under the optimal flocculation conditions. Moreover, the extraction rate was 94.5 % under the optimal extraction conditions. Excitingly, the heat-triggered flocculation-to-extraction behavior of DFP could be realized with a coupled system, which then minimized the drawbacks of a single unit. In this coupled system, the extraction mechanism changed from chemical extraction to physical extraction, which avoided unnecessary loss of decolorization rate. Furthermore, the recycling and reuse of waste resources could be achieved through stripping and the next round of direct dye baths. Therefore, this work provided a new methodology for the development of novel pollutant removal systems with dual-functional materials, achieving the reuse of waste resources and improving the quality of treated water.