# Modified Kapok Fibers (_Ceiba pentandra_ ([PERSON]) for Oil Spill Remediation
## 2 Materials and Methods
### Surface Treatments  
Activation processes were developed based on thermal, acid, and alkali treatments as shown in the flowchart in Figure 1.  
Figure 1: Preparation flowchart. Initial collection and preparation stage, with thermal, acid, and alkali activations and applications.  
To perform the acid and alkaline treatments, a specific apparatus was prepared using a 250 mL Erlenmeyer flask to keep the material submerged, since it is exceptionally hydrophobic and, hence, floats, hampering a homogenous contact between fibers and each treatment solution. Briefly, a helicoidal galvanized wire was placed on top of the flask (Figure 2a) to hold the kapok fiber in place and submerged in the solution, assuring that the whole surface of the material remains in contact with the solutions, even with the soft stirring applied (Figure 2b).  
A kapok sample of 0.1 g was weighed on a Shimadzu ATX224 scale (Kyoto, Japan) and placed on a previously cleaned and dried Petri dish. The sample was then heated under applied air circulation in a 7 LAB lab oven, model SEDi-C 40L (Rio de Janeiro, Brazil), for 8 h. After the heating period, the samples were taken out of the oven, cooled down for approximately 10 min, and their sorptive capacities were promptly measured. The temperature treatments were performed at 60, 70, 80, 90, 100, and 120 \({}^{\circ}\)C, and the experiments were conducted in duplicates.  
For the acid activation, kapok fibers were submitted to an acidic medium using hydrochloric acid (37% P.A. ACS Q. Moderna) at room temperature (20 \({}^{\circ}\)C), based on an adjusted version of the method proposed by [PERSON], [PERSON], and [PERSON] (2012). A 0.1 g kapok sample was placed in the apparatus described in Figure 2a, submerged in a 200 mL solution of HCl at different concentrations (0.01, 0.1, 1.0, and 2.0 mol.L\({}^{-1}\)), and the system was fixed onto a stirring table (SOLAB model SL-180/DT (Piracicaba, SP, Brazil)) and stirred at 150 rpm for 50 min. The experiment time was chosen, following the work of [PERSON], [PERSON] and [PERSON] (2012), because according to these authors, this was the best time granted to guarantee an increase in sorption, since after this value, the extensive degradation of the fiber by the treatment agents was observed [22]. After the reaction time, the fibers were filtered and washed with distilled water six times (filling the volume of the filter and emptying it--20 mL) to remove residual acid and any dissolved impurities, and then placed inside the oven at 50 \({}^{\circ}\)C until a constant mass was reached. Sequentially, the material was taken out of the oven, cooled down for 10 min, and the sorptive capacity was measured in duplicate.  
The alkaline treatment was performed using sodium hydroxide (NaOH, P.A., Dinamica) at room temperature (20 \({}^{\circ}\)C). The same methodology applied to the acid experiment was followed here, using 200 mL solutions of NaOH at concentrations of 0.01, 0.1, 1.0, and 2.0 mol.L\({}^{-1}\). After 50 min of contact with the basic solution, the fibers were washed with distilled water (6 times, 20 mL each) and dried in an oven at 50 \({}^{\circ}\)C. The assays were conducted in duplicated.  
Figure 2: (a) Apparatus used to hold the kapok fibers inside an Erlenmeyer flask; (b) Kapok sample forcibly kept in contact with treatment solution (acid or alkaline).