# Integrated Process for Ballot Bin Waste Vaporization for High-Quality Cellulose Acetate Recovery
## 3 Results and Discussion
### Acetone Precipitation of Cellulose Acetate and Characterizations  
The final stage in cellulose acetate purification was based on the dissolution/precipitation strategy. It should be mentioned that cellulose acetate (CA) is soluble in different organic solvents depending on the number of hydroxyl moieties substituted by acetyl groups, i.e., the degree of substitution (DS). Generally, when the DS is larger than two (like in  
Figure 3: FT-IR spectrum of ethanol extractives form BBW. the case of WCBs), common solvents such as tetrahydrofuran, acetone, or dioxane can be used [63]. On the contrary, when DS < 2, CA can be dissolved in fewer solvents, for example, acetic acid [43]. In the present study, CA was dissolved in acetone, since it is a greener, cheaper, and more commercially available solvent compared to the others listed above. The insoluble material (removed by centrifugation) was a dark brown heterogeneous material composed mostly of burned filter parts and other residues, and it was not further investigated. The cellulose acetate was then precipitated by putting the clear solution in water as an antisolvent. Finally, 30 \(\pm\) 4 g of cellulose acetate was recovered by filtration and drying as a white, fluffy material from 35 g of clean filter (Figure 2). The final product, CA, was characterized by the means of different analytical tools. The precipitation from acetone strongly reduced the metal concentrations (Table 1, row 7), probably due to a double mechanism, as follows: either during the water precipitation or by removing insoluble parts where heavy metals were chelated. The levels of heavy metals in the final cellulose acetate were generally quite low. The cellulose acetate recovered (from five experiments) was also deeply chemically characterized by \({}^{1}\)H-NMR, GPC, FT-IR, and UV and compared to the cellulose acetate present in an unsmoked filter (Figure 4). The FT-IR spectrum (Figure 4, panel A) confirms that the recovered material was cellulose acetate. This was evidenced by the appearance of peaks related to acetate groups, i.e., those at 1740 cm\({}^{-1}\) and 1220 cm\({}^{-1}\), referring to the C=O stretching and C-O stretching in acetyl esters, and those at 1369 and 1420 cm\({}^{-1}\), peaks arising from the symmetric bending vibration of C-H in the methyl groups, respectively [64; 65]. The signals located at ca. 2950 and 1030 cm\({}^{-1}\), resulting from the C-H stretching vibrations of sp\({}^{3}\) hybridized C atoms and the C-O stretching of alcoholic and etheric bonds, respectively, are related to the structure of the cellulosic backbone [61]. Finally, the presence of the broad band at 3000-3600 cm\({}^{-1}\) refers to O-H stretching and, therefore, enlightens us that there is a partial substitution of -OH with acetyl acetate groups. The \({}^{1}\)H-NMR spectrum (Figure 4, panel B) further confirms the structure of the cellulose acetate through the appearance of strong signals within the chemical shift range of 1.8-2.2 ppm assigned to methyl hydrogens in acetate groups. Moreover, the presence of many superimposed peaks in the chemical  
Figure 4: Typical analyses of the final CA recovered. Panel (**A**): FT-IR; panel (**B**): \({}^{1}\)H-NMR; panel (**C**): Gel Permeation Chromatography (GPC); and panel (**D**): UV-Vis. The structure of diacetylcellulose in used as a reference. shift range of 3.5-5.5 ppm, which refers to the protons belonging to the anhydride glucose units (AGUs) of the cellulose chain, was detected [52]. The peak at ca. 2.8 ppm is due to water traces, as reported by [PERSON] et al. [63]. The data regarding the degree of substitution determined by the FT-IR analysis, the molecular weights, and the dispersity index (D) achieved by the GPC analysis are reported in Table 2. The data from the unsmoked filter (used as a reference), in terms of the DS, molecular weights, and dispersity index, confirmed that the purification procedure retained the chemical properties of pristine cellulose acetate.