Imidazolium-based cationic polymeric nanotraps for efficient removal of Cr2O72-

Two imidazolium-based cationic polymeric nanotraps based on tetraphenylmethane building blocks (CPN-tpm) with different counterions were rationally designed and constructed for the efficient removal of Cr2O72- from wastewater. The influence of counterions on Cr2O72- adsorption performance was studied. With better wettability (contact angle as 28.61°), CPN-tpm-Cl exhibited a higher uptake capacity of 366 mg g−1 for Cr2O72- capture and a faster ion exchange kinetic process in 20 min. While CPN-tpm-Br with a contact angle of 83.16° showed a lower maximum capacity of 324 mg g−1. In addition, CPN-tpm-Cl can work in a wide pH range from 2 to 10 and possess excellent selectivity (such as Cl-, NO3- and SO42-) as well as good reusability for 5 times. Such excellent performances indicated that CPN-tpm-Cl is a promising candidate for the Cr2O72- capture application. Our work not only contributes cationic polymeric nanotraps as a promising candidate for Cr2O72- removal, but also suggests a new approach to develop new type of adsorbents for wastewater treatment.