Cationic Surfactant-Modified Covalent Organic Frameworks for Nitrate Removal from Aqueous Solution: Synthesis by Free-Radical Polymerization.

Development of efficient adsorbents for nitrate removal is vital for tackling increasing nitrate contamination. We report a free-radical polymerization strategy to prepare a cationic surfactant-modified covalent organic framework (DhaTab-S) for removing nitrate ions from aqueous solution. DhaTab-S was prepared by grafting a cationic surfactant diallyldimethylammonium chloride solution on vinyl-containing COF (DhaTab-V). The adsorption capacity for nitrate was pH-dependent with the maximum at pH 6, and the adsorption process was largely influenced by ionic strength. The adsorption equilibrium for nitrate on DhaTab-S was reached within 40 minutes and followed pseudo-second-order kinetics. DhaTab-S showed a nitrate adsorption capacity of 108.8 mg g-1 , which is about 15 times that of COF before surfactant modification. The large adsorption capacity makes DhaTab-S a promising candidate for nitrate removal from aqueous media.