Fluffy ball-like magnetic covalent organic frameworks for adsorption and removal of organothiophosphate pesticides

Organothiophosphate pesticides (OPPs) are the most commonly used pesticides, and their environmental migration brings serious water pollution and significant danger to human health, and thus it is urgent to develop effective technologies for removal of OPPs from water. Herein, magnetic covalent organic framework (COF) with a triazine skeleton was fabricated for enhanced adsorption and removal of OPPs from water. Magnetic COF has a fluffy ball-like structure, high crystallinity, large BET surface area (1543 m2 g-1), and regular mesopores (~3.1 nm). Therefore, it displayed high adsorption rates and large adsorption capacities for four typical OPPs, pyridafenthion, phoxim, pyrimitate, and phorate. Based on adsorption kinetic and isotherms investigations, the batch experimental data of magnetic COF was effectively modeled by pseudo-second-order kinetics and the Freundlich isothermal model. The equilibrium adsorption capacities of magnetic COF composite for OPPs ranged from 163.9 to 178.6 mg g-1, which were about 10 times higher than the amorphous magnetic composite. The adsorption mechanism was further explored to verify the contributions of π-π, CH⋯π, and CH⋯S interactions to the adsorption of OPPs on the crystalline magnetic COF. Furthermore, the high removal rate of OPPs from the environmental water and reusability further indicated its potential in real applications as an effective adsorption material.