Preparation and optimization of porous regenerated cellulose microspheres from cellulose tetraethyl-ammonium/urea solution for adsorption of cationic methylene blue dye

Porous regenerated cellulose microspheres (RCMs) have attracted increasing attention due to their wide range of applications from medical carriers to environmental remediation. Here, porous RCMs were synthesized for adsorption of cationic methylene blue dye using a simple emulsification–acid coagulation–oven-drying technique after dissolving pulp cellulose with a degree of polymerization (DP) of approximately 1500 in tetraethylammonium hydroxide (TEAOH)/urea solvents at room temperature. The RCMs with controllable size (20 to 224 µm) and high pore volume (8.24 to 10.20 mL/g) were prepared by varying the dosage of the surfactant polyoxyethylene sorbitan monooleate (polysorbate 80). Moreover, the viscosity of the cellulose solution steadily decreased with storage time due to the decrease in cellulose DP, but the effect on the particle size and morphology of RCMs was negligible, which could be advantageous to the scalable production of RCMs. When used as an adsorbent for cationic methylene blue dye removal, it showed high adsorption efficiency (1 h to achieve equilibrium, 24.5 mg/g), stability, recyclability, and reusability.