Highly-porous uniformly-sized amidoxime-functionalized cellulose beads prepared by microfluidics with N-methylmorpholine N-oxide

Uniformly-sized porous cellulose beads functionalized with amidoxime groups were prepared for the first time using a microfluidic method with N-methylmorpholine N-oxide (NMMO) monohydrate as a cellulose solvent. The molten state cellulose dope in NMMO monohydrate (cell/NMMO dope) as a disperse phase and hot mineral oil as a continuous phase were used in a T-junction microfluidic chip to produce uniformly-sized cell/NMMO droplets. Coagulation of the molten state cell/NMMO droplet at high temperature and amidoxime functionalization could prepare the highly-porous spherical amidoxime-functionalized cellulose beads with a uniform fibrous open internal structure. The prepared amidoxime-functionalized cellulose beads showed excellent metal adsorption properties with a maximum adsorption capacity of ~ 80 mg g⁻¹ in the case of Cu²⁺/phthalate ions. The newly developed highly-porous cellulose beads can open many new applications with other proper functionalization at the reactive hydroxyl groups of the cellulose. Graphic abstract: [Figure not available: see fulltext.]