# Modified Kapok Fibers (_Ceiba pentandra_ ([PERSON]) for Oil Spill Remediation
## 3 Results and Discussion
### Characterization of Natural and Treated Materials
#### 3.2.2 SEM
(2020) attributed the bulkier sorption capacities presented by natural materials to be more associated with the structural features than the functional groups on the surface, as these are more decisive to the initial interaction and assurance of binding [21]. Additionally, the treatment with 2.0 mol/L HCl, according to Figure 6e, shows that the acid may attack the tubular structure of the fiber and, after the partial removal of the wax, reduce the mechanical resistance, which causes bents and fissures, reducing the intratubular retention capacity. Similarly to the thermal treatment, the acid treatment, therefore, is not an economical method, especially considering that the best conditions found merely equaled the behavior seen for the natural untreated fiber, and it is not easily applicable at an industrial scale,given the effort spent during the procedure and the necessity of neutralizing the acid effluent afterwards. The following activation is the alkali activation, where after the treatment at a concentration of 0.1 mol/L, the lumen remains open, with smooth inner walls and an approximate 24.4 um diameter (Figure 7a). The superficial structure at 5000-fold magnification shows low roughness (Figure 7b), resembling the kapok in natura, and the general disposition of the fibers highlights cylindric tubular clusters with a homogenous distribution right above the wax layer (Figure 7c). The micrographs of the fibers treated with NaOH 2.0 mol/L, on the other hand, display flattened structures without defined tubular forms, and even when these are present, they have narrower lumens, with diameters in the range of 16 um and rough inner walls, and what appears to be a structure that confers mechanical resistance, the lignin, exposed within the lumen. With a 5000\(\times\) magnification (Figure 7e), it becomes evident that the material  
Figure 7: Micrographs with different magnifications of kapok fibers treated with NaOH solutions. Treatment with 0.1 mol/L: (**a**) lumen structure (1000\(\times\)), (**b**) surface (5000\(\times\)), (**c**) disposition and condition of the fiber (300\(\times\)). Treatment with 2.0 mol/L: (**d**) lumen structure (2400\(\times\)), (**e**) surface (5000\(\times\)), (**f**) disposition and condition of the fiber (240\(\times\)), (**g**) advanced merecization process on the fiber caused by the alkaline treatment (2.0 mol/L NaOH). suffered extensive deterioration. The roughness observed comes from the lignin and hemicellulose themselves, which are exposed in structural arrays following the direction of the fibrous material. Figure 7f demonstrates a cluster of fibers treated at 2.0 mol/L, which reached a degradation state such that lost their cylindrical character with large portions of flat forms, diverse bent forms, and deformations, were either caused by a shedding that accompanies the loss of wax or by the accumulation of these non-polar compounds from neighboring areas. Focusing on one single fiber mercerized at 2.0 M NaOH, as shown in Figure 7g, it is possible to see the degree of degradation of the surface hydrophobic layers due to the alkaline attack; the more external region accumulates a ragged waxy layer, which presents several gaps in regions that were previously completely covered. The hydrophilic cellulosic region can also be seen, which justifies the negative effect, in terms of oil sorption, observed for the fiber submitted to this condition. Thereby, it is fair to infer that the alkaline treatment is not a viable option to improve the oil sorption capacity of kapok fibers either, since the alterations that the material went through, under the best condition found (1.0 mol/L), balance the beneficial effects with the degradation of the biomass; these effects cancel one another out, and the treated material capacity only equals the natural fiber.