# Modified Kapok Fibers (_Ceiba pentandra_ ([PERSON]) for Oil Spill Remediation
## 3 Results and Discussion
### Characterization of Natural and Treated Materials  
#### 3.2.1 FTIR  
The FTIR spectra of the fibers submitted to temperatures of 90 and 120 \({}^{\circ}\)C (Figure 4a) show larger absorption stretches at 3410 cm\({}^{-1}\) linked to the presence of free hydroxyl groups, indicating a reduction in the layer covering the surface of the material, the breakage of hydrogen bonds of hemicellulose and cellulose, and increasing the hydrophilic character of the material. The 60 \({}^{\circ}\)C treatment decreased this band, reinforcing the statement that this temperature merely dries the material, reducing the free water content without altering its surface structural integrity. For the same treatment, it is noteworthy that the stretches at 2914-2918 cm\({}^{-1}\), related to CH\({}_{2}\) and CH\({}_{3}\) groups, remain unaltered for the low-heat assay, whereas for 90 and 120 \({}^{\circ}\)C temperatures, these signals slightly increased, suggesting the exposure of internal carbonic chain layers. This is also stressed out by the enlargement of the signal at 1736 cm\({}^{-1}\), which was consistent with the increase in temperature. These results imply that the proportion of esters, ketones, and carboxylic acids on the surface of the system increased due to the heat; hence, this indicates that part of the lignin may have been uncovered. The intensity of the signals between 1505 and 1602 cm\({}^{-1}\) was reduced; this region concentrates the Csp\({}^{2}\) bond of both aromatic and aliphatic compounds, which were likely vaporized during the process. The C-O stretching bands between 1300 and 1000 cm\({}^{-1}\) greatly expanded, once again confirming the exposure of the internal cellulosic material, which is coherent with the decrease in oil sorption observed in Figure 4a. Thus, the FTIR analyses suggest the prevalence of a higher concentration of carbon chains on the surface, probably caused by the ascension of internal layers, as well as the exposure of cellulosic material, which are the reasons for the new array. The effects of these morphological modifications of the surface non-polar layer can be seen by comparing the SEM micrographs in Figure 4, showing that the temperature alters two main characteristics of the material: the lumen disposition and the surface roughness. Analogous to the thermal treatment, the results of Figure 4b show an enhancement in the absorption peaks centered at 3410 cm\({}^{-1}\), coherent with the rise in acid concentration, denoting those acidic conditions either degraded or removed the surface hydrocarbons and lead to breakages of the hydrogen bonds, exposing the OH-rich cellulosic structure. It is also noteworthy that the intensification of the peaks at 2914 cm\({}^{-1}\), corresponding to hydrocarbon chains, and at 1736 cm\({}^{-1}\), related to carbonyl groups, coincided with the elevation of acidity of the media, suggesting this treatment may change the distribution and arrangement of these groups on the fiber surface, in addition to the exposure of lignin and reduction in surface wax. This is corroborated by the increase in the carbon-oxygen stretch at 1245 cm\({}^{-1}\), commonly associated with ester moieties. Lastly, the most prominent signal of the spectra is the 1050 cm\({}^{-1}\) C-O stretch, which denotes the disclosure of the polysaccharides, such as glucose, which is a negative effect that may lead to a loss in structural capacity in terms of rigidity whilst the acid concentration is increased. This result also indicates a new arrangement of species on the surface or the removal of non-polar compounds. The next step consisted in the analysis of the effect of the acidic media on the topography of the fibers, comparing the SEM micrographs shown in Figure 5, which presents the materials treated with lowest, 0.1 mol/L, and highest, 2.0 mol/L, acid concentrations. The FTIR spectra, Figure 4c, of the fibers treated with the NaOH solution were also analyzed to evaluate the effect of the alkaline treatment on the surface functional groups.