2. Experimental
2.1. Materials
Printed paper waste was used as the raw material. 1-methylimidazole (Sigma Aldrich), allyl chloride (Sigma Aldrich) and sodium hydroxide (NaOH, Merck) were used without further purification. Ultrapure water (∼18.2 MΩ, 25 °C) was prepared using the Water Purifying System (ELGA, Model Ultra Genetic).
2.2. Pretreatment process
Printed paper waste was grounded and macerated by soaking in water and stirred continually at 2000 rpm for 2 h. The filtered sample was treated with 12% NaOH for about 12 h. Treated cellulose pulp was washed with distilled water and dried in an oven at 60 °C until constant weight.
2.3. Synthesis of ionic liquid
AMIMCl was synthesized based on the method as described previously [10]. Typically, 1-methylimizole and allyl chloride at a volume ratio of 1:2 were stirred and refluxed at 50–60 °C for 8 h in a 500 mL round-bottomed flask. Unreacted allyl chloride was removed by a rotary evaporator.
2.4. Preparation of cellulose beads
Cellulose beads were prepared from a homogeneous cellulose solution formed by dissolving cellulose fibers in an ionic liquid, AMIMCl. 200 mg cellulose pulp was dissolved in 5 mL of AMIMCl at 100 °C with stirring to obtain a clear and viscos cellulose solution (4 wt%). Cellulose beads were formed by extruding the cellulose solution through a 5-mL disposable syringe with needle into a coagulation bath of ultrapure water at room temperature. Syringe needles of different diameters (1.20 mm, 0.80 mm, 0.50 mm) were used to produce cellulose beads of different mean sizes. Cellulose beads were solvent exchanged with acetone of different percentages in order to remove water, and subsequently dried using a carbon dioxide supercritical point dryer.
2.5. Sample characterization
Cellulose beads were characterized using a Scanning Electron Microscope (SEM) (JEOL Model JEM-1230). The mean mass and diameter of cellulose beads were determined from at least of 50 beads using electronic balance and micro-gauge respectively. Specific surface areas (SBET) of cellulose beads were measured by the BET Surface Area Analyzer (Quantachrome Autosorb iQ-AG) based on nitrogen gas sorption at 77 K and analyzed by with Quantachrome AS1Win software (Quantachrome Instruments Version 2.01).