Waste treats waste: Facile fabrication of porous adsorbents from recycled PET and sodium alginate for efficient dye removal

Abstract

Dye-contaminated water and waste plastic both pose enormous threats to human health and the ecological environment, and simultaneously solving these two issues in a sustainable and resource-saving way is highly important. In this work, a sodium alginate-polyethylene terephthalate-sodium alginate (SA@PET) composite adsorbent for efficient dye removal is fabricated using wasted PET bottle and marine plant-based SA via simple and energy-efficient nonsolvent-induced phase separation (NIPS) method. Benefiting from its porous structure and the abundant binding sites, SA@PET shows an excellent methylene blue (MB) adsorption capacity of 1081 mg g−1. The Redlich–Peterson model more accurately describes the adsorption behavior, suggesting multiple adsorption mechanisms. In addition to the electrostatic attractions of SA to MB, polar interactions between the PET matrix and MB are also identified as adsorption mechanisms. It is worth mentioning that SA@PET could be recycled 7 times without a serious decrease in performance, and the trifluoroacetic acid-dichloromethane solvent involved in the NIPS process has the possibility of reuse and stepwise recovery. Finally, the discarded adsorbent could be completely degraded under mild conditions. This work provides not only a composite adsorbent with excellent cationic dye removal performance for wastewater treatment, but also an upcycling strategy for waste PET.