FTIR Spectroscopy Morphology Results and Discussion 1. Yield of Cellulose Extraction

ISBN : 978-602-17761-0-0 37 © 2013 Published by Center for Pulp and Paper through REPTech2012 Pre-treatment with 2-naphthol can improve the extractability during deligniication step since it was reacted as a carbonium ion scavenger [12]. Previous study [13] explained the mechanism how ionic liquids, 1-allyl-3-methylimidazolium chloride AmimCl dissolve cellulose. It is assumed that a similar mechanism is followed in the case of the dissolution of kapok iber in deep eutectic solvent DES. The mixing of choline chloride and urea at 74 o C results in signiicant depression of freezing point that arises from an interaction between urea molecules and the chloride ion [14].The ion pairs in DES dissociate into individual anion and cation ions. Free anion ions associate with cellulose hydroxyl protons and free cation ions associate with cellulose hydroxyl oxygen groups. These dislocate hydrogen bonding in cellulose and cause its dissolution. Low dissolution of DES compared to AmimCl might be due to the cations of DES relatively reduced the effective anion concentration [15]. However, DES is more preferable because it is inexpensive [10]. Ethanol organosolv process was carried out to isolate cellulose from the kapok iber in the third method. The aims of the process are similar to the other two methods which are to remove hemicellulose, deligniication and recover the cellulose fraction [16]. At the end of the process, a solid and a liquid fraction remain. The solid fraction is rich in cellulose and the liquid fraction contains hemicelluloses and lignin fraction. Aqueous processing in this study used water, kapok iber and sulphuric acid as catalyst for hydrolysis reactions. When these treatments are carried out under mild conditions, hemicelluloses are depolymerized leading to sugar oligomers [11]. Higher yield obtained for cellulose extracted using organosolv treatment method revealing that the cellulose was almost not affected by the autohydrolysis process. Autohydrolysis was performed to achieve fractionation which mainly related to the solubilization of hemicelluloses. Aqueous solution of ethanol 80:20 reacted as reagent to solubilize lignin. A similar behaviour was observed by other researchers using wheat straw [17].

3.2. FTIR Spectroscopy

Fig. 1 shows FTIR spectra for raw kapok, standard cellulose and obtained cellulose of all three extraction methods. The broad band around 3400 cm -1 observed in all the FTIR spectra is attributed to OH group, meanwhile the peaks at 2900 cm -1 shows the C-H stretching of aliphatic =CH 2 and –CH 3 . Fig. 1b shows the FTIR spectra of purchased standard cellulose and was used as comparison. FTIR spectra for raw kapok Fig. 1 a show two peaks at 1739 cm -1 and 1251 cm -1 due to the carbonyl groups of hemicelluloses. This is in agreement with the results reported by previous researches [18]. These two peaks were not observed in Fig. 1 c, d and e indicating that all the three methods used removed hemicelluloses successfully. Aromatic skeletal vibrations of lignin give three strong peaks at 1597, 1505 and 1420 cm -1 at raw kapok FTIR spectra Fig. 1a. These peaks of lignin were disappeared in other FTIR spectra. These results are in line with the results observed by other researchers [19]. The peaks that attributed to cellulose can clearly be observed around 1330 cm -1 O-H in plane deformation, 1160 cm -1 C-O-C asymmetric stretching and 898 cm -1 glucose ring stretching, C 1 -H deformation for all the spectra [19,20].

3.2. Morphology

SEM micrographs of raw kapok, standard and obtained cellulose are shown in Fig. 2. A silky appearance can be seen for raw kapok iber a. Fig. 2 shows that raw kapok iber has smooth surfaces, tubular structure, buoyancy and lufiness. This result Fig. 1. FTIR Spectra of a Raw Kapok; b Standard Cellulose; Cellulose Obtained by c Conventional; d Dissolution in DES; e Organosolv Treatment Methods 38 © 2013 Published by Center for Pulp and Paper through REPTech2012 is similar to previous report by other researchers [7]. There is a total loss of air entrapment inside obtained cellulose Fig. 2 c. The structure became wholly lattened and similar to a lat ribbon-like structure. The surface topography is rougher than before treatment. This is due to the decrease in spiral angle around the iber axis and increase in molecular orientation. A fair amount of randomness is introduced into the orientation of the crystallites due to the removal of non-cellulosic matter [21]. As an example, the obtained cellulose has similar appearance with the standard cellulose in terms of surface topography as shown in Fig. 2.

3.3. Thermal Stability