## 3 Results and Discussion
Indeed, the highest content of aliphatic \(\mathbf{C}\) is found for Sample 3, which is the sample obtained with the lowest amount of H\({}_{2}\)O\({}_{2}\) (0.0006 %wt), while the highest content of linked to heteroatoms is obtained for the Sample 1, in which the quantity of H2O2 was the highest (0.002 %wt). These results indicate that: a) the Fenton treatment is able to make changes in the initial OFMSW matrix; b) HR-MAS 13C NMR spectroscopy is effective in appreciating the variations that individual families of compounds undergo following the different treatments, in terms of reagent concentrations used. \begin{table}
\begin{tabular}{c c c c c} \hline  & _Caliph (\%)_ & \(\mathcal{C}_{X}\) (\%) & \(\mathcal{C}_{unsat}\) (\%) & \(\mathcal{C}_{curb}\) (\%) \\ \hline
**Sample 0** & \(54\pm 1\) & \(32\pm 3\) & \(9\pm 1\) & \(5\pm 1\) \\
**Sample 1** & \(43\pm 1\) & \(44\pm 1\) & \(9\pm 1\) & \(4\pm 1\) \\
**Sample 2** & \(53\pm 2\) & \(28\pm 5\) & \(13\pm 1\) & \(6\pm 1\) \\
**Sample 3** & \(56\pm 1\) & \(31\pm 1\) & \(8\pm 1\) & \(5\pm 1\) \\
**Sample 4** & \(60\pm 1\) & \(26\pm 1\) & \(5\pm 1\) & \(9\pm 1\) \\ \hline \end{tabular}
\end{table} 
Table 2: Integral values, in percentage, of different carbon type, aliphatic (\(\mathcal{C}_{aliph}\)), heteroatoms-linked (\(\mathcal{C}_{X}\)), unsaturated (\(\mathcal{C}_{unsat}\)) and carbonylic (\(\mathcal{C}_{curb}\)), calculated for the Samples 0, 1, 2, 3, and 4 at 12 h.  
Figure 2: (**a**) HR-MAS 13C\(-\)[1H] NMR spectrum of Sample 0 (in blue) compared with CP-MAS 13C NMR spectrum of OFMSW sample reported in the literature (in black) [26]; (**b**) HR-MAS 13C NMR spectrum of Sample 0 and signal assignment. In the box, the comparison with the CP-MAS spectrum of starch in the same region is shown [31]. The experiments just described show that the NMR HR MAS method provides relevant information on the composition variations of the organic fraction of the waste subjected to the Fenton treatment. In order to better understand what happens to the various families of compounds during the oxidative process and to investigate the best reaction conditions, the HR-MAS NMR technique was applied to the study of two oxidative processes, A and B, carried out in different reaction conditions, as described in Section 2.1. A total of nine samples were collected for the two processes, four for process A and five for process B. For these samples, no alterations were observed in the profile of the \({}^{13}\)C HR-MAS NMR spectra, but there are marked variations in the areas of the values associated with each region of the spectra. The results for process A are reported in Table  
* **Process A. ** From the data reported in Table 3 and Figure 4, it can be deduced that the reaction proceeds according to two main steps. The first stage, stage I, goes from 0 up to 9 h: during this time, as the reaction proceeds, a decrease in the content of carbon atoms linked to heteroatoms is observed. Since the data present in the literature on organic waste show that the amount of carbons linked to oxygen (C-O) is greater than the amount of any other C-X [23], it is probable that this also occurs for our samples and, therefore, this decrease can be attributable, for example, to the oxidation of alcoholic groups, mostly present in sugars, to carbonyl groups. On the other hand, however, there is no substantial variation in the areas related to the carbon atoms of the carbonyl groups and this suggests that probably, in this period of time, further oxidation of carbonyl groups with loss of CO2 occurs. It should be emphasized that it cannot be deduced in any way from the recorded spectra as to whether the CO2 produced comes from the newly formed or pre-existing carbonyl groups. Stage II occurs around 12 h: at this time, there is an evident increase in the area of carbon atoms linked to heteroatoms due, probably, to an oxidation of aliphatic carbons and, to a lesser extent, to the unsaturated ones. As evidence of this, a decrease in the areas due to these carbon groups can be appreciated. * **Process B.