Fabrication of porous copolymer with ionized carboxyl groups for highly efficient removal of crystal violet from water

Development of porous adsorbents tethered with ionic pendent groups is conducive to establish an efficient dye removal strategy in aqueous solution. Herein, a porous copolymer with carboxyl negative ions, termed as Poly(AA-co-DVB), was fabricated via one-step solvothermal copolymerization of acrylic acid with divinylbenzene and subsequent alkali treatment. Characterizations showed that Poly(AA-co-DVB) was rich in mesoporous structure and had a large specific surface area of 473.6 m² g⁻¹. The prominent structural feature endowed Poly(AA-co-DVB) with a high adsorption capacity of 604.5 mg g⁻¹ for targeted contaminant crystal violet (CV) at 298 K. The influences of various factors on adsorption performance of Poly(AA-co-DVB) for CV were studied in detail. The adsorption process conformed to the Langmuir isotherm, pseudo-second-order kinetic and intraparticle diffusion models, in which the CV removal was endothermic and spontaneous in nature. Coexisting ions Na⁺ and Ca²⁺ promoted the CV removal, while Al³⁺ suppressed the CV removal. Notably, after four cycles of adsorption–desorption, a slight increase in adsorption capacity was observed, demonstrating the excellent reusability of Poly(AA-co-DVB). The analysis of FT-TR, zeta potential, and XPS revealed that electrostatic attraction and π-π stacking contributed to the CV removal by Poly(AA-co-DVB).