Porous cellulose beads reconstituted from ionic liquid for adsorption of heavy metal ions from aqueous solutions

Modified porous cellulose beads (MCBs) with typical sizes ranging from 2 to 3 mm were successfully fabricated via acidic precipitation from the cellulose dissolved in ionic liquid, followed by surface-grafting with aminoguanidine hydrochloride using glutaric anhydride as a coupling agent. The nano-sized calcium carbonate (30% wt on dry cellulose) was added to cellulose solution prior to the precipitation in acidic medium in an attempt to promote the formation of the pore structure of cellulose beads. Modified cellulose powders (MCPs) (size 150 μm) were prepared by precipitating the solution of the cellulose which reacted with glutaric anhydride homogeneously in ionic liquid, followed by grafting with aminoguanidine hydrochloride. The pseudo-second-order kinetic model and the Langmuir isotherm model described the adsorption process well. The maximum adsorption capacities of MCBs towards Hg(II) and Cu(II) were 581.4 and 94.88 mg/g; whereas the maximum adsorption capacities of MCPs for Hg(II) and Cu(II) were 625 and 98.52 mg/g, respectively. The results demonstrated that both MCBs and MCPs are highly effective and promising as green-based adsorbents for the removal of heavy metal ions in aqueous systems, Hg 2+ in particular.