Rosin-derived porous microspheres with robust selective cationic dye adsorption

The utilization of rosin to fabricate functional polymers has attracted great attention due to its unique structure and property. Herein, we prepared a new type of carboxyl-containing cross-linked rosin microspheres (CCRMs) using a renewable-resource rosin as the raw material through the suspension polymerization. For comparative purpose, vanillin methacrylate (VMA), styrene (St) and isobornyl methacrylate (IBOMA) were separately used to replace DAGMA as monomer for the preparation of microspheres. Our results indicated that the obtained porous CCRMs showed a broad size distribution ranging from mesopores (3–50 nm) to macropores (> 50 nm), whereas the counterparts derived from VMA, St or IBOMA showed a powder state. Moreover, the CCRMs exhibited moderately high thermal stability. The integration of DAGMA into polymer microspheres provided CCRMs with excellent adsorption ability, which exhibited robust selective cationic dye (e.g., methylene blue (MB) and crystal violet (CV)) adsorption from waste aqueous solution. The adsorption process was fitted well with the Langmuir isotherm and the pseudo-second-order kinetic model. The maximum adsorption capacity was observed to be 602.4 mg/g for CV at 40 °C, and 512.8 mg/g for MB at 20 °C. In general, the high dye adsorption properties suggest that CCRMs may be highly efficient in adsorption selectivity for some cationic dyes.