Piperazine-triazine incorporated calix[4]pyrrole polymers with high nitrogen content by Mannich reaction for rapid and efficient iodine adsorption from water

The rapid and efficient removal of radioiodine from water is a challenging and meaningful task to safeguard human health. Herein, two calix[4]pyrrole-based polymers were prepared through Mannich reaction between nitrogen-rich 2,4,6-tri(piperazin-1-yl)-1,3,5-triazine (TPT) and two configurational isomers of tetra- meso resorcinol-functionalized calix[4]pyrrole (2α2β-CP and 4α-CP), referred as 2α2β-CP-TPT and 4α-CP-TPT, respectively. The nitrogen contents of 2α,2β-CP-TPT and 4α-CP-TPT were as high as 15.11 % and 14.84 %, respectively. Accompanied by the bowl-shaped calix[4]pyrroles, the CP-TPTs showed high vapor iodine uptake, especially 4.82 g/g for 4α-CP-TPT. More importantly, the CP-TPTs exhibited rapid adsorption kinetics for capture iodine from aqueous phase, with the 2α,2β-CP-TPT at 1 mg/mL level showing a k 2 value as high as 7.374 × 10 −3 g/(mg min). In addition, high iodine adsorption capacity for 2α,2β-CP-TPT and 4α-CP-TPT were achieved to be 1989.6 and 2812.6 mg/g from water, respectively. Even more impressive was the removal efficiency above 98 % in flow-through applications even at flow rate as high as 10 mL/min and in simulated seawater conditions. The CP-TPTs could also exhibit high dynamic iodine adsorption capacity from water as well as excellent stability and outstanding reusability. Adsorption mechanism study discovered the foundational role of the charge transfer interaction on the excellent adsorption performance of the CP-TPTs. All these features demonstrated promising application prospects of the CP-TPTs for iodine removal from water.