Journal of Science: Advanced Materials and Devices xxx (2017) 1e7 Contents lists available at ScienceDirect Journal of Science: Advanced Materials and Devices journal homepage: www.elsevier.com/locate/jsamd Original Article Surface modification of cellulose isolated from Sesamun indicum underutilized seed: A means of enhancing cellulose hydrophobicity Adewale Adewuyi a, b, *, Fabiano Vargas Pereira b a b Department of Chemical Sciences, Faculty of Natural Sciences, Redeemer's University, Ede, Osun State, Nigeria ^nio Carlos, 6627, Pampulha, CEP 31270-901 Belo Horizonte, MG, Brazil Department of Chemistry, Federal University of Minas Gerais, Av Anto a r t i c l e i n f o a b s t r a c t Article history: Received 25 May 2017 Received in revised form 10 July 2017 Accepted 20 July 2017 Available online xxx Cellulose (SC) isolated from sesame seed (SS) was surface modified with the introduction of an ester functional group via a simple reaction to produce the modified product (SA) SS, SC and SA were characterized using Fourier transform infrared (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TG), particle size distribution (PSD), zeta potential and scanning electron microscopy (SEM) SC and SA were evaluated for their water holding capacity (WC), oil holding capacity (OC), swelling capacity (SW) and their ability to adsorb heavy metals The FTIR revealed peaks corresponding to the formation of the ester functional group at the surface of SA The crystallinity of SC was 28.02% but after the modification it increased to 77.03% in SA The PSD of SC and SA was both monomodal with sizes of 10.1305 mm in SC and 10.2511 mm in SA The adsorption capacity of SC towards Pb (II) and Cu (II) ions was higher than that of SA However, SA was unable to adsorb Cu (II) ions SA exhibited the lower WC and SW values as compared to SC which suggested an improved hydrophobicity after the modification This study has shown that hydrophobicity can be improved in cellulose via surface modification © 2017 Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) Keywords: Cellulose Hydrophobicity Modification Sesamum indicum Underutilized seed Introduction With the recent increase in demand for products made from renewable and sustainable non-petroleum based resources, cellulose is gaining significant recognition for diverse applications due to its renewability, biodegradability, non-toxicity and molecular structure It represents the most abundant renewable polymer which is mostly used in the form of fibers or derivatives Cellulose has been reported from a number of conventional sources, which are of both plant and microorganism origins [1] However, there is still a need to search for better alternatives as most of the previously identified conventional sources are expensive On the other hand, these sources have found other applications Sesame seed (Sesamum indicum) is an underutilized plant material in Nigeria which can serve as a source of cellulose This plant belongs to the Pedaliaceae family [2] It is about 60e120 cm tall and the fruit is a dehiscent capsule held close to the stem When ripe, the capsule shatters to release a number of small seeds The seeds * Corresponding author Department of Chemical Sciences, Faculty of Natural Sciences, Redeemer's University, Ede, Osun State, Nigeria E-mail address: walexy62@yahoo.com (A Adewuyi) Peer review under responsibility of Vietnam National University, Hanoi are ovate, slightly flattened and thin The seed oil has been reported as an important source of phytonutrient for applications in food and pharmaceutical industries [3] The seed is an important source of oil and after oil is extracted from the seed, the seed cake left is usually discarded as waste Presently, the seed cake is considered as waste with no specific use The essence of this work is to find application for this discarded seek cake in Nigeria Due to the wide range of potential applications and important inherent properties of cellulose, there is a continuous effort on how to improve and optimize the properties of cellulose-based natural fibers Among these important inherent properties of cellulose, the hydrophobicity plays an important role in water repellency, selfcleaning, corrosion prevention, friction reduction and antifouling [4] The poor hydrophobicity of cellulose has limited its application in a few areas of research such as in waste water treatment or purification Previous studies have shown that the properties of cellulose can be improved by surface modification [5] So, replacing the hydroxyl functional groups at the surface of cellulose via surface modification might be an effective means of improving on its hydrophobicity In this regard, the present study is aimed at finding a cheap source of cellulose, which can be surface modified in order to improve its hydrophobicity This was achieved by isolating, http://dx.doi.org/10.1016/j.jsamd.2017.07.007 2468-2179/© 2017 Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/) Please cite this article in press as: A Adewuyi, F.V Pereira, Surface modification of cellulose isolated from Sesamun indicum underutilized seed: A means of enhancing cellulose hydrophobicity, Journal of Science: Advanced Materials and Devices (2017), http://dx.doi.org/10.1016/ j.jsamd.2017.07.007 A Adewuyi, F.V Pereira / Journal of Science: Advanced Materials and Devices xxx (2017) 1e7 characterizing and surface modifying cellulose from a sesame seed To the best of our knowledge, there is no report on the isolation and surface modification of cellulose from the sesame seed source from Nigeria Experimental acetic acid, diluted to L of distilled water) and aqueous sodium chlorite (1.7 wt% NaClO2 in deionized water) The mixture was then stirred at 80 C for h The resulting fibers were washed repeatedly in deionized water until the pH of the fiber became neutral The bleaching step was repeated twice until the fiber became completely white and dried in an air-circulating oven at 50 C for 24 h giving rise to SC of an estimated yield of about 25% 2.1 Materials 2.3 Modification of SC SS was obtained from a local market in Ibadan, Oyo state, Nigeria This was later identified at the Department of Botany and Microbiology, University of Ibadan, Ibadan, Oyo state, Nigeria The seeds were air dried, ground in an industrial mill and stored in an airtight container Sodium chlorite, sodium hydroxide, acetic acid, chloroacetic acid, suberic acid, thionylchloride, ethylenediamine and all other chemicals used in this study were purchased from SigmaeAdrich (Brazil) 2.2 Isolation of cellulose from SS The isolation of cellulose from SS was achieved following the method described by Flauzino Neto et al [6] Briefly, 200 g of SS was transferred into a L beaker containing alkali solution (2 wt% NaOH) This was heated at 80 C for h with continuous stirring using a Fisatom mechanical stirrer The beaker with its content was cooled, filtered, washed continuously with deionized water several times until alkali free and oven dried at 50 C The residue obtained was bleached with a mixture of solution, which was made up of equal volumes (1:1) of acetate buffer (27 g NaOH and 75 mL glacial Chloroacetylchloride was synthesized by stirring a mixture of chloroacetic acid (0.03 mol), thionylchloride (0.04 mol) and chloroform at 75 C for 30 SC (7.50 g) was added to the chloroacetylchloride (after the removal of excess thionylchloride under reduced pressure); this was allowed to react for h under constant stirring at 80 C and finally cooled in ice Suberic acid (50 mL) was added and stirred for h at 80 C under reflux Cold distilled water was added to the mixture and centrifuged thrice for 10 at 8500 rpm to remove excess suberic acid The final product was dried at 50 C for 24 h giving rise to an SA yield of about 80% 2.4 Characterization The functional groups in SS, SC and SA were determined using FTIR (Perkin Elmer, spectrum RXI 83303) SS, SC and SA were blended with KBr, pressed into pellets and analyzed in the range of 400e4500 cmÀ1 The X-ray diffraction pattern was obtained using X-ray diffractometer (XRD-7000X-Ray diffractometer, Shimadzu) with filtered Cu Ka radiation at 40 kV and 40 mA XRD pattern was Fig FTIR spectra of the sesame seed (a), the sesame cellulose (b) and the modified sesame cellulose (c) Please cite this article in press as: A Adewuyi, F.V Pereira, Surface modification of cellulose isolated from Sesamun indicum underutilized seed: A means of enhancing cellulose hydrophobicity, Journal of Science: Advanced Materials and Devices (2017), http://dx.doi.org/10.1016/ j.jsamd.2017.07.007 A Adewuyi, F.V Pereira / Journal of Science: Advanced Materials and Devices xxx (2017) 1e7 recorded from 10 to 80 C of 2q/s with a scanning speed of 2.00 / Thermal stability and fraction of volatile components of SS, SC and SA were monitored by DTA-TG apparatus (SHIMADZU, C30574600245) under nitrogen atmosphere, while the surface morphology was studied using FEI quanta 200 (model EDAX EDS) that operates on Genesis software (version 5.21) The PSD was carried out using a zeta potential analyzer (DT1200, Dispersion technology) at 25 C, while observing a general calculation model for irregular particles Several measurements were taken using Dispersion technology-AcoustoPhor Zetasize 1201 software (version 5.6.16) 2.5 Water holding capacity A known weight (0.5 g) of SC and SA was separately dispersed in 10 mL of distilled water in a pre-weighed, clean centrifuge tube (W) placed in a water bath at 37 C for 30 These were centrifuged for 15 at 4000 rpm; the supernatant was removed and the centrifuge tube with the distilled water soaked SC and SA was weighed (W2) WC was estimated as [7]: ðW À W ỵ W ịị WC g g1 ¼ W1 (1) 2.6 Oil holding capacity This was determined by weighing 0.2 g (W) of SC and SA separately into a calibrated centrifuge tube containing mL (V1) of Picralima nitida seed oil The mixture was properly stirred for 10 after which it was centrifuged for 30 at 5000 rpm The supernatant oil (V2) was gently removed, while the absorbed oil was estimated as the difference between V1 and V2 OC was calculated as described by Lu et al [8]: V ÀV OC mL gÀ1 ¼ W (2) 2.7 Swelling capacity SW was determined by placing 0.5 g (W) of SC and SA in a calibrated tube, the initial bed volume (V1) was measured, mixed with 10 mL of distilled water and shaken vigorously The tube with its content was placed in a water bath at 25 C for 24 h and the final volume (V2) measured SW was calculated as [9]: V ÀV SW mL gÀ1 ¼ W (3) 2.8 Heavy metal adsorption capacity Lead nitrate (Pb(NO3)2) and copper sulfate (Cu(SO4).5H2O) salts were used in the preparation of the salt solutions in de-ionized water Metal adsorption study was carried out by separately shaking 0.1 g of SC and SA with a 50 mL solution (100 mg/L) of metal in different beakers at 25 C and 200 rpm for h This was later centrifuged for 10 at 5000 rpm, and the metal concentration before and after adsorption were determined using Atomic Fig TG curves of the sesame seed (a), the sesame cellulose (b) and the modified sesame cellulose (c) Please cite this article in press as: A Adewuyi, F.V Pereira, Surface modification of cellulose isolated from Sesamun indicum underutilized seed: A means of enhancing cellulose hydrophobicity, Journal of Science: Advanced Materials and Devices (2017), http://dx.doi.org/10.1016/ j.jsamd.2017.07.007 A Adewuyi, F.V Pereira / Journal of Science: Advanced Materials and Devices xxx (2017) 1e7 Absorption Spectrometer (Varian AA240FS) The metal ions adsorption capacity of SC and SA was calculated as qe ¼ ðCo À Ce ÞV M (4) where qe is the adsorption capacity in mg/g, Co and Ce are initial and final concentrations (mg/L) of adsorbate (Pb and Cu) in solution respectively; while V and M are volumes (L) of metal ion solution and weight (g) of SC and SA used Results and discussion 3.1 Characterization The FTIR result is presented in Fig The spectra revealed peaks corresponding to the OH functional group at 3320 cmÀ1 The band at 1745 cmÀ1 only found in SS was assigned to the C]O stretching of the acetyl group and the uranic ester groups of the hemicellulose, which may also be due to the ester linkage of the carboxylic group in the lignin and hemicelluloses The band at 1745 cmÀ1 disappeared in SC which may be due to the removal of hemicellulose and lignin from SS but reappeared in SA which suggests the formation of the ester functional group in SA Bands corresponding to the amorphous characteristics of the cellulosic materials were seen at 354 cmÀ1 in SS, SC and SA while the band at 2911 cmÀ1 was assigned to the CeH stretching of CH2 in SS, SC and SA The peaks at 1094 and 1155 cmÀ1 was attributed to the deformation of the CeH rocking vibration and the CeOeC pyranose ring skeleton, while the peak at 894 cmÀ1 was assigned to the symmetric CeOeC stretching of the b-1,4-glycosidic linkages of the glucopyranose units of the cellulose in SS, SC and SA Cellulose and its derivatives tend to carbonize under heating through dehydration and cross-linking reactions, which can be described as the rearrangement of a cellulose structure that promotes the final production of char residue SS, SC and SA were pyrolyzed in order to investigate their effects of temperature and thermal stability as shown in Fig Loss in mass was first noticed in the temperature range of 85e115 C, which was attributed to the loss of internal water molecules in SS, SC and SA There was another loss in mass within the temperature range of 115e162 C that may be assigned to the loss of volatile organic compounds The loss in mass in the range of 189e320 C may be attributed to the loss of hemicellulose Loss in mass at temperatures above 450 C in SS and SC were assigned to losses of lignin and char [10] There was steady loss in mass in SA at temperatures above 320 C, which can be described as the loss in mass at 320e450 C, 450e600 C and 600e715 C This steady loss in mass was considered as being due to the chain length of the suberic acid involved in the modification This increase in the decomposition temperature of SA may be an indication of the thermal stability of the cellulose that was increased with the modification The diffraction pattern presented in Fig with 2q peaks is typical of cellulose I structure The crystallinity index (Ic) was determined using the height of 200 peak (I002, 2q ¼ 21.65 ) and the minimum intensity between the 200 and 110 peaks (IAM, 2q ¼ 17.75 ) which can be expressed as: Fig X-ray diffraction patterns of the sesame seed (a), the sesame cellulose (b) and the modified sesame cellulose (c) Please cite this article in press as: A Adewuyi, F.V Pereira, Surface modification of cellulose isolated from Sesamun indicum underutilized seed: A means of enhancing cellulose hydrophobicity, Journal of Science: Advanced Materials and Devices (2017), http://dx.doi.org/10.1016/ j.jsamd.2017.07.007 A Adewuyi, F.V Pereira / Journal of Science: Advanced Materials and Devices xxx (2017) 1e7 I IAM Ic %ị ẳ 002 100 I002 (5) where I002 represents both crystalline and amorphous materials while IAM represents the amorphous material The crystallinity of SC was 28.02% but after the modification it increased to 77.03% in SA The increase in crystallinity may be due to the introduction of the ester group to the cellulose which may likely have reinforced the crystalline nature of the cellulose The particle size distribution of SC and SA was found to be monomodal The size distribution was found to be 10.1305 mm for SC and 10.2511 mm for SA The zeta potential is presented in Fig The values of the zeta potential increased in SC and SA just as the pH value increased The value of the zeta potential is suggestive that SC and SA are stable materials The SEM micrograph is presented in Fig The surface of SS appears to have irregular shape and size which seemed to be composed of several microfibrils with each fiber having a compact structure Surface of SC is different from that of SS, it appeared smooth and flaky which may be due to the removal of Fig Zeta potentials of the sesame cellulose (a) and the modified sesame cellulose (b) Fig SEM images of the sesame seed (a), the sesame cellulose (b) and the modified sesame cellulose (c) Please cite this article in press as: A Adewuyi, F.V Pereira, Surface modification of cellulose isolated from Sesamun indicum underutilized seed: A means of enhancing cellulose hydrophobicity, Journal of Science: Advanced Materials and Devices (2017), http://dx.doi.org/10.1016/ j.jsamd.2017.07.007 A Adewuyi, F.V Pereira / Journal of Science: Advanced Materials and Devices xxx (2017) 1e7 hemicellulose, lignin and some other non-cellulosic materials while SA appears to be stacked particles of aggregated macromolecules; it exhibited a lumpish structure which may be due to the intramolecular interaction in the molecule The surface of SA is completely different from those of SS and SC 3.2 Water holding, oil holding and swelling capacities of SC and SA The values obtained for WC, OC and SW with respect to SC and SA are presented in Fig WC was found to be 17.0372 g/g for SC and 2.6116 g/g for SA WC estimates the ability of SC and SA to hold water over a period of time, especially when subjected to an external centrifugal gravity or compression forces The values obtained for WC were lower in SA compared to SC, which may be due to the modification that might have improved the hydrophobicity of SA The value of WC for SA is also lower than those reported for the red bean flour [11] and the white lupin [12], but higher than that reported for the standard flour [13] OC can be related to the adsorption of organic compounds to the surface of SC and SA, which can be linked to the porosity of the structure of SC and SA [14] The value obtained for SA (4.0302 mL/g) was higher than that of SC (2.6165 mL/g) These values are lower than those reported for Polythia longifolia [15] but higher than those for the cowpea [16] and the white lupin [12] SW estimates the amount of water that SC and SA can absorb at a given time The value was found to be higher in SC (3.6860 mL/g) than in SA (1.9488 mL/g) This once again shows an improved hydrophobicity in SA over SC These values are lower than those reported for the coconut kernel [14] and the cowpea [16] 3.3 Heavy metal adsorption capacity Heavy metals have been known to enter the human body through food chain and most time cause serious harm to human health as a result of the disease they bring Exposure to polluted water is one of the key sources of this problem in developing countries [17,18] This may be caused by contamination from materials with strong affinity for heavy metal adsorption Use of materials with low affinity for heavy metal adsorption is of interest during certain industrial applications like in the case of food and cosmetic industries SC and SA were evaluated for their ability to adsorb Cu (II) and Pb (II) ions from an aqueous solution The Table Comparison of the adsorption of Pb (II) and Cu (II) ions on SC and SA with other adsorbents reported in the literature Adsorbent Pb (II) Cu (II) Reference Adansonia digitata Goethite Rice husks Banana peel Bionanocomposite Cotton fiber Modified polyamineepolyurea Coconut tree sawdust Cicer arietinum ZnO/MMT Chitosan-coated bentonite Modified silica SC SA 54.417 109.20 6.69 89.286 224.97 21.62 109.90 25.00 20.69 88.50 13.49 65.54 20.681 0.888 9.349 37.25 3.25 5.720 169.817 6.12 73.50 3.89 17.77 54.06 12.14 104.12 5.695 Nil [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] Present study Present study Note: Values are in mg/g adsorption capacities varied with SC showing the higher adsorption capacity towards the studied metals The results obtained for the adsorption capacities of SC and SA are presented in Table 1, these are also compared with those reported previously in the literature The adsorption capacity of SC towards Cu (II) was 5.695 mg/g, while SA was unable to adsorb Cu (II) ions from the solution, probably due to the inability of the modified surface to interact with the Cu (II) ions in the solution SA may not be able to interact with Cu (II) ions because of the conversion of the hydroxyl group at its surface to the ester functional groups as a result of the modification Moreover, the ester group lacks hydrogen atoms which could have been exchanged for the Cu (II) ion like in the case of the hydrogen atom in the hydroxyl group This reduction in the metal adsorption capacity of SA suggests that the modification has taken place This suggests that SA may find applications, where interference from Cu (II) is not required or of limited importance SC was also found to have the higher adsorption capacity for Pb (II) ion which was 20.681 mg/g while the value obtained for SA was 0.888 mg/g This also showed that SA has little attraction for Pb (II) ions The value obtained for SA was far lower than those reported in the literature Conclusion Cellulose was isolated from SS with an estimated yield of 25%, thanks to the surface modified using the suberic acid In this case, the hydroxyl group at the surface of SC was found to be converted to the ester functional group The improved hydrophobicity was indicated by the reduced WC and SW after the modification The SA exhibited the low adsorption capacity towards Pb (II) ions, but it was unable to adsorb Cu (II) ions from an aqueous solution This suggests that SA may find potential applications where interference from Cu (II) is not required or of limited importance Acknowledgments This research was supported by TWAS-CNPq The authors are also grateful to TWAS-CNPq for awarding a 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enhancing cellulose hydrophobicity, Journal of Science: Advanced Materials and Devices (2017), http://dx.doi.org/10.1016/ j.jsamd.2017.07.007 ... press as: A Adewuyi, F.V Pereira, Surface modification of cellulose isolated from Sesamun indicum underutilized seed: A means of enhancing cellulose hydrophobicity, Journal of Science: Advanced Materials... press as: A Adewuyi, F.V Pereira, Surface modification of cellulose isolated from Sesamun indicum underutilized seed: A means of enhancing cellulose hydrophobicity, Journal of Science: Advanced Materials... F.V Pereira, Surface modification of cellulose isolated from Sesamun indicum underutilized seed: A means of enhancing cellulose hydrophobicity, Journal of Science: Advanced Materials and Devices