Fast and efficient removal of paraquat in water by porous polycalix[n]arenes (n = 4, 6, and 8)

Abstract

Herbicide paraquat (dimethylviologen) is a major water pollutant threatening ecosystems and human health. Therefore, it is crucial to develop materials to remove it from water. Three calix[n]arene-based (n = 4, 6, 8) porous organic polymers with different cavity sizes of the backbone macrocycle (CX4P, CX6P, CX8P) were synthesized and tested for their potential use in toxic paraquat removal. These polymers reached some of the highest reported maximum uptake capacities (Q_max up to 419 mg g⁻¹) and showed high adsorption rate constants (k_obs up to 0.179 g mg⁻¹ min⁻¹). Importantly, the materials could be easily regenerated by simple washing methods and reused without significant losses in their efficiency while still outperforming commercial activated carbon currently used in water purification.