Adsorption behavior of Rhodamine B on nanoporous polymers

Abstract

Nanoporous polymers were successfully synthesized by copolymerization of divinylbenzene and 1-vinylimidazolate (PDVB-VI-x, x = 0.2, 0.33, 0.5, in which x stands for the PDVB/VI molar ratio), and used to adsorb Rhodamine B (RhB) from aqueous solution. Characterizations of PDVB-VI were performed using scanning electron microscopy, N₂ adsorption/desorption isotherms, Fourier transform infrared spectroscopy and thermogravimetric analysis. PDVB-VI exhibited a high surface area, large pore volume and oleophilic nature, which is beneficial for organic dye adsorption. To study the adsorption behavior of PDVB-VI for the removal of RhB in detail, PDVB-VI-0.2 was selected as an example. The effects of pH value, adsorbent dosage, contact time and temperature were studied. The results indicated that the maximum adsorption capacity of the adsorbent for RhB was 260.42 mg g⁻¹ at 298 K. The adsorption behavior could be well described by the pseudo-second-order kinetics model, and the experimental data followed the Langmuir isotherm model. The thermodynamics parameters indicated that the adsorption process was spontaneous and exothermic. Remarkably, the adsorbent can be reused four times after treating it with ethanol. Furthermore, PDVB-VI-0.2 was also used as an adsorbent for the removal of other dyes, such as Acid Blue 1 and Ponceau S, with an adsorption capacity of 90.84 mg g⁻¹ and 9.62 mg g⁻¹, respectively. These results demonstrate that PDVB-VI samples are a new kind of potential industrial adsorbent for the removal of organic dye from aqueous solution.