C/W emulsion-templated macroporous anionic monolith: Application for dye removal

A clean, sulfonated, highly adsorptive macroporous monolith was constructed using a carbon dioxide-in-water (C/W) high internal phase emulsion template. The random copolymerization of N-hydroxyethyl acrylamide and sodium styrene sulfonate in the water phase was initiated with persulfate. The chemical composition of the novel sulfonated monolith was confirmed by Fourier transform infrared spectroscopy and energy-dispersive X-ray spectroscopy, and the interconnected pore structure was confirmed by scanning electron microscopy (SEM). Results showed that the void sizes were 47-92 mu m and that the interconnected pore throats were approximately 10-30 mu m. Such a hydrophilic, anionic macroporous material exhibited excellent adsorption properties for cationic dyes. The maximum adsorption capacity of the monolith for methylene blue (MB) and malachite green (MG) reached 1,316 and 2,624 mg/g, respectively, in 500-800 mg/L dye solution at 25 degrees C. Furthermore, the kinetics and thermodynamic parameters of the adsorption process were examined. Experimental data exhibited that adsorption kinetically followed the pseudo-second-order model. The removal rates of MG and MB both exceeded 90% after six regenerations. The adsorption mechanism of the adsorbent was demonstrated preliminarily. The dynamic adsorption operation of MB was conducted in a fixed column, and the breakthrough curve data were fitted using the Thomas and bed depth service time models. All these findings indicated the potential industrial applications of adsorptive sulfonated macroporous monolith.