# Integrated Process for Ballot Bin Waste Vaporization for High-Quality Cellulose Acetate Recovery
## 3 Results and Discussion
### Water Washing  
Water washing has been recognized as an effective method for the cleaning of cigarette butts [35; 47] without the addition of any other chemicals, thus minimizing treatment costs and mainly preserving the chemical properties of the cellulose acetate. Alkaline and acidic conditions have been recognized to help in the purification of cigarette butts [56], efficiently removing heavy metal contaminants and/or organic compounds. Nevertheless, these conditions are likely to promote deacetylation and/or depolymerization reactions on the cellulose acetate polymer [60]. Since the goal of this research was to recover pure cellulose acetate with pristine chemical characteristics, we avoided the use of such conditions. The water washing was also able to remove, besides heavy metals and other inorganics, water-soluble organic compounds (such as glues, plasticizers, and smoke residues) and defibrillate the tipping paper under heating and vigorous stirring. It was possible to recover a fraction called smoked filters with an average weight of 43 \(\pm\) 4 g (starting from 100 g of BBW), along with 21 \(\pm\) 3 g of pulp paper (Figure 2). The total recovery yield was around 90%; the lost parts were likely the water-soluble components reported above. Simple water washing, as reported in Table 1, row 4, was able to remove 91% of Cu, 59% of Cr, 92% of Fe, 100% of Mn, 55% of Ni, 62% of Pb, and 68% of Zn. These findings are consistent with other research reported the literature that was conducted using the same conditions [56; 61]. In fact, as reported by [PERSON] [56], Cu, Fe, and Mn (removal efficiency higher than 90% in this work) have the highest concentrations of metals leached from smoked cigarette material measured after a specified period of soaking. The effect of water washing in the purification of cellulose acetate was also explored by [PERSON] et al. [35]. Factors like pH and ionic strength could affect the amount of metal released [57] and a clear effect of conditions (NaCl vs. sodium acetate vs. sulfuric acid) was observed in terms of metal extraction, with the best results with H2 SO4 0.02%. According to the authors, the acidic solution seemed to be the most efficient for the extraction of Al, Fe, \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline  & **As** & **Cd** & **Co** & **Cu** & **Cr** & **Fe** & **Mn** & **Ni** & **Pb** & **Zn** \\ \hline Ballot bin waste & nd & nd & nd & 5.0 \(\pm\) 3.4 & 0.4 \(\pm\) 0.3 & 351.0 \(\pm\) 328.5 & 39.0 \(\pm\) 26.6 & 2.7 \(\pm\) 1.5 & 0.6 \(\pm\) 0.4 & 7.9 \(\pm\) 5.6 \\ Cigarette butts & nd & nd & nd & 5.0 \(\pm\) 3.4 & 0.3 \(\pm\) 0.2 & 383.6 \(\pm\) 284.4 & 2.4 \(\pm\) 1.4 & 2.3 \(\pm\) 1.5 & 1.3 \(\pm\) 1.4 & 10.9 \(\pm\) 2.2 \\ Ashes & nd & nd & nd & 6.0 \(\pm\) 1.0 & 0.2 \(\pm\) 0.1 & 170.5 \(\pm\) 14.7 & 53.6 \(\pm\) 9.7 & 1.5 \(\pm\) 0.6 & nd & 11.5 \(\pm\) 0.7 \\ Smoked filters & nd & nd & nd & 0.6 \(\pm\) 0.5 & 0.2 \(\pm\) 0.1 & 49.4 \(\pm\) 39.0 & nd & 1.7 \(\pm\) 1.4 & 0.8 \(\pm\) 0.6 & 5.6 \(\pm\) 3.9 \\ Washing waters * & nd & nd & nd & 2.5 \(\pm\) 0.4 & nd & 49.25 \(\pm\) 27.5 & 8.6 \(\pm\) 5.6 & 1.56 \(\pm\) 0.9 & 1.6 \(\pm\) 1.1 & nd \\ Clean filters & nd & nd & nd & 0.7 \(\pm\) 0.5 & 0.3 \(\pm\) 0.2 & 39.6 \(\pm\) 9.9 & nd & 2.0 \(\pm\) 1.4 & 1.8 \(\pm\) 0.2 & 5.9 \(\pm\) 2.2 \\ Cellulose acetate & nd & nd & nd & 1.3 \(\pm\) 0.4 & 0.3 \(\pm\) 0.2 & 9.1 \(\pm\) 0.9 & nd & 2.0 \(\pm\) 0.3 & 0.3 \(\pm\) 0.2 & 2.0 \(\pm\) 0.3 \\ \hline \end{tabular}
\end{table} 
Table 1: Heavy metal content expressed in ug/g (* or mg/L) in the different fractions recovered during the purification process. Data are expressed as an average \(\pm\) interval of confidence (n = 3, \(p\) = 0.05). Cu, and Zn. Our results indicated that, even in neutral conditions (without the addition of any chemicals), a high removal efficiency was obtained; this was explained by the higher temperature of the water, as used by [PERSON] et al. [47].