Three-dimensional fluorinated pyrazinium-based cationic organic polymers with high charge density for enhanced ReO4- removal

Ultrafast separation of hazardous and radioactive anions from strongly alkaline nuclear wastewater is urgently needed for both the public health and environment, but also extremely challenging. Herein, we report a 3D fluorinated pyrazinium-based cationic organic polymer (TBPM-Fpz) with high charge density for ultrafast and selective removal of ReO4-. Using fluorinated pyrazine as the linker and rigid tetraphenylmethane as the building block, a high charge density and relatively hydrophobic diamond-like topology skeleton of TBPM-Fpz was constructed, which is beneficial to improve the affinity for ReO4- and promote thorough exposure of active sites. Batch sorption experiments revealed that TBPM-Fpz is a rare example that can integrate ultrafast sorption kinetics (equilibrium within 3 min), high capacity (833.01 mg g(-1)), and excellent selectivity towards ReO4- (92.34% in 1000 times excess of SO42-) in one adsorbent. In addition, TBPM-Fpz achieve high ReO4- removal efficiency in simulated Savannah River Site High-Level Waste stream (95.32%, solid-to-liquid ratio: 40:1) and simulated Hanford Low Activity Waste wastewater (89.76%, solid-to-liquid ratio: 1:1). Experimental and computational results indicate that the superior performance is attributed to fluorination that increases charge density and decrease the steric hindrance. This study shows the enormous potential of fluorinated cationic organic polymer for enhanced ReO4- removal from strongly alkaline wastewater, providing valuable insights into designing high-performance cationic organic polymers for alkaline nuclear waste treatment.

Automated summary

This study reports a rare 3D fluorinated pyrazinium-based cationic organic polymer (TBPM-Fpz) that can selectively remove hazardous and radioactive anions from nuclear wastewater at an ultrafast rate. The polymer exhibits fast sorption kinetics, high capacity, and excellent selectivity towards ReO4-. It also shows high removal efficiency in simulated high-level and low activity waste streams.