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Nano porous alkaline earth metal silicates as free fatty acid adsorbents from Crude Palm Oil (CPO)

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Nano porous alkaline earth metal silicates as free fatty acid adsorbents from Crude Palm Oil (CPO)

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  1. Nano porous alkaline earth metal silicates as free fatty acid adsorbents from Crude Palm Oil (CPO) Indra Masmur, Seri Bima Sembiring, Nimpan Bangun, Jamaran Kaban, and Nabila Karina Putri Citation: 1803, 020052 (2017); doi: 10.1063/1.4973179 View online: http://dx.doi.org/10.1063/1.4973179 View Table of Contents: http://aip.scitation.org/toc/apc/1803/1 Published by the American Institute of Physics

  2. Nano Porous Alkaline Earth Metal Silicates as Free Fatty Acid Adsorbents from Crude Palm Oil (CPO) Indra Masmur1,a) Seri Bima Sembiring2,b), Nimpan Bangun2, Jamaran Kaban3 and Nabila Karina Putri2 1Doctoral Chemistry Program, University of Sumatera Utara, Medan, Indonesia 2Laboratory of Inorganic Chemistry, Faculty of Mathematic and Sciences, University of Sumatera Utara, Medan, Indonesia 3Laboratory of Organic Chemistry, Faculty of Mathematic and Sciences, University of Sumatera Utara, Medan, Indonesia Corresponding author: intar76@yahoo.coma) bima_depari@yahoo.comb) Abstract. Free fatty acids(FFA) from Crude Palm Oil (CPO) have been adsorbed by alkaline earth metal silicate (M- silicate : M = Mg, Ca, Sr and Ba) adsorbents in ethanol using batch method. The adsorbents were prepared from the chloride salts of alkaline metals and Na2SiO3. The resulting white solid of the alkaline earth metal silicates were then heated at 800oC for 3 hours to enlarge their porosities. All adsorbents were characterized by SEM-EDX, XRD and BET. The EDX spectrum of SEM-EDX showed the appearance of all elements in the adsorbents, and the XRD spectrum of all adsorbents showed that they have crystobalite structure. The porosity of the adsorbents calculated by BET method showed that the porosities of the adsorbents range from 2.0884 - 2.0969 nm. All the adsorbents were used to adsorb the FFA from CPO containing 4.79%, 7.3%, 10.37% and 13.34% of FFA. The ratio of adsorbent to CPO to be used in adsorption of FFA from CPO were made 1:1, 1:2 and 1:3, with adsorption time of 1 hour. We found that the maximum adsorption of FFA from CPO was given by Ca-Silicate adsorbent which was between 69.86 – 94.78%, while the lowest adsorption was shown by Mg-silicate adsorbent which was 49.32 -74.53%. INTRODUCTION Indonesia is the largest CPO producer in the world [1], where in 2015 it was produced about 32.500.000 tons and about26.400.000 tons is exported[2]. All the exported CPO must fulfil The Indonesian National Standard (SNI). The quality of CPO is determined by its free fatty acid (FFA), and it must be less than5% [3]. The quality of the CPO is also determined by the quality of the Fresh Fruit Bunch (FFB), to be milled. The FFB are generally suppliedfrom 3 (three) sources i.e. from government’s plantations, private’s plantations and small holder. The FFB from government and private plantations are generally milled at the day of the crop, and the obtained CPO hasthe FFA content about 1 - 2,3% of FFA, while the CPO obtained from the people’s plantations are generally contain higher FFA content which can reach >5% [4]. Since the area of small holder’s plantationsare about 42% of the total area of palm oil plantations in Indonesia, they will give a potential contribution to the CPO export. In order to improve the quality of that CPO, especially from the small holder’s plantation, it is needed to reduce the FFA content from the CPO. There are at least 2 (two) methods that have been introduced to reduce the FFA content from CPO i.e.by esterification and adsorption.From these 2 methods, adsorption is likely to be more interesting because it is simple, low cost and the adsorbent can be recovered and regenerated [5]. Recently, Mg-silicate and Ca-silicate have been used to adsorb FFA from CPO[6,7].Clowutimonet.al. [7]haveused Mg-silicate prepared from rice husk and Na2SiO3 to adsorb FFA from CPO. They found that the adsorbent with SiO2/MgO ratio of 1.99 had the high adsorptioncapacity of 185 mg of FFA per gram of adsorbent. Justamanet.al. [8] used 4 adsorbents, M-PSS (M= Mg, Ca, Sr and Ba; PSS = polystyrenesulfonate) to adsorb carotenoids from CPO and they reported that empty d-orbital of the alkaline earth metals (Mg, Ca, Sr and Ba) can International Symposium on Applied Chemistry (ISAC) 2016 AIP Conf. Proc. 1803, 020052-1–020052-7; doi: 10.1063/1.4973179 Published by AIP Publishing. 978-0-7354-1471-6/$30.00 020052-1

  3. interact with the olefin bond of carotenoids bypolar-polar interaction. In the same way, it is also possible that the adsorption of FFA by alkaline earth silicates by polar-polar interaction through empty d-orbitals of the alkaline earth metals with the oxygen atom of the FFA. Bangunet.al. have also demonstrated that nano porous MgSiO3 and CaSiO3 can be used to adsorb FFA from extracted carotenoids CPO containing 4.47 % of FFA. They reported that MgSiO3 and CaSiO3 can adsorb the FFA in that CPO about 68-72% and 77-87%, respectively. However, they have not reported the role of the other two elements in the group i.e. strontium and barium, therefore it is also interesting to further study of the adsorption properties of strontium and barium silicates. In this paper we report our finding on the study of nano porous alkaline earth metal silicates, M-silicates (M = Mg, Ca, Sr and Ba) as free fatty acid adsorbents from crude palm oil (CPO). EXPERIMENTAL Materials and Instruments MgCl2, CaCl2, SrCl2, BaCl2,ethanol and water glass (Na2SiO3) were purchased from E-Merck, Crude Palm Oil (CPO) was obtained from PT. Perkebunan Negara III, Medan in 4 containers, after keeping in the Laboratory for about 3-4 years theFFA content of the CPO were 4.79% (A), 7.35% (B), 10.37% (C) and 13.34% (D).The FFA contents were determined by gas chromatography (Agilent type 7890 B; column type DB5HT). Surface areas and porosities were determined by Surface Area Analyzer (Micromeritics Tristar II 3020, N2 gas carrier), SEM image and elemental analysis were recorded by SEM-EDX, (Carl Zeiss EVO MA Oxford EDS X-Max 50 mm2),the Crystal structures were determined by X-Ray Diffraction Spectrometer(6100Shimadzu). Preparation of adsorbents The adsorbents, alkaline metal silicate, MgSiO3, 1, CaSiO3,2, SrSiO3,3, BaSiO3, 4, were prepared from MCl2 (M=Mg, Ca, Sr, Ba) and Na2SiO3 in water. The solution mixture of MCl2 and Na2SiO3was stirred at RT for 3 h and the resulting white precipitate was filtered, washed with ethanol and placed in afurnace at 800ºC for 3 h.Surface morphology of theadsorbents were characterizedby tandem SEM-EDX, Crystalline Structures by X-Ray Diffraction Spectrometer,and Surface Areas and Porosities were determined by Surface Area Analyzer followed by Burnaeur- Emmet-Teller (BET) and Barret-Joyner-Hallenda (BJH) calculation. Adsorption of FFA Every adsorbent, 1, 2, 3 and 4, was divided into parts: 0.5 g, 1.0 g and 1.5 g each, and the amount of CPO weighted for A, B, C and D were 0.5 g each and dissolved in of ethanol (15 ml). Adsorbent 1(0.5 g) was added to ethanolic solution of CPO,A, (0.5 g; 15 ml) and the mixture was stirred for 30 min., then the adsorbent and the filtrate was separated in a centrifuge. The FFA content in filtrate was determined by Gas Chromatography. The same procedure was applied to adsorb FFA from A by adsorbent1 using 1.0 g and 1.5 g, respectively. This was repeated for CPO solution of B, C and D. Again, this procedure was repeated to adsorb FFA from CPO solution of A, B, C and Dusing adsorbents 2, (0.5 g, 1.0 g, 1.5 g), adsorbent 3 (0.5 g, 1.0 g, 1.5 g) and adsorbent 4 (0.5 g, 1.0 g, 1.5 g). RESULTS AND DISCUSSION Adsorbents 1, 2, 3and 4have been prepared from MgCl2, CaCl2, SrCl2 and BaCl2 respectively with Na2SiO3 in water. All adsorbents were characterized as follows: SEM image. The SEM images of 1, 2, 3 and 4 with 3000 times magnification are shown in Figure 1. The SEM image of 1 shows a rough surface with some little holes, while the SEM image of 2 shows beside a rough surface there are also some needle like shape. On the other hand the SEM image of 3 shows a rough surface with agglomeration, while the image of 4 shows a big slab with a rough surface. 020052-2

  4. MgSiO3 CaSiO3 SrSiO3 BaSiO3 FIGURE 1. SEM Image of MgSiO3, CaSiO3, SrSiO3 and BaSiO3 EDX elemental analysis Energy Dispersive X-ray (EDX) spectra of 1, 2, 3 and 4 are shown in Figure 2. All spectra of 1, 2, 3 and 4 are similar and the peaks that appeared in the spectra are consistent with the elements in adsorbents 1, 2, 3 and 4. 020052-3

  5. MgSiO3 CaSiO3 SrSiO3 BaSiO3 FIGURE 2.EDX spectra of MgSiO3, CaSiO3, SrSiO3 and BaSiO3 Surface Area and Porosity Surface areas of the adsorbents 1, 2, 3and 4were determined by Surface Area Analyzer followed by BET and BJH methods and the results are tabulated in Table 1. From Table 1, the surface areas of 1, 2, 3 and 4, as calculated by BET method are 5.1920 m2/g, 3.3185 m2/g, 2.7084 m2/g and 2.5154 m2/g respectively. The surface areasbecome smaller from 1, 2,3 to 4. The same things are happened for the surface areas of pore of 1, 2, 3 and 4 as calculated by BJH method are 2.804m2/g, 2.005m2/g, 1.810m2/g and 1.601 m2/g, respetively. The pore volume are also smaller from1, 2, 3 to 4, On the other hand the particle size of 1, 2, 3 and 4 are larger from 1, 2, 3 to 4, while the pore size are almost the same for all adsoerbents which are between 2.0089 nm to 2.0969 nm, and therefore they are all nano porous adsorbents. TABLE 1. Surface area, pore volume, pore size and particle size of Mg-silicate, Ca-silicate, Sr-silicate and Ba-silicate MgSiO3 BET surface area (m2/g) 5.1920 BJH surface area of pores (m2/g) Pore volume (cm3/g) 0.001470 Pore size (nm) 2.0969 Nanoparticle size (nm) 1155.6337 XRD Analysis X-raydiffractogram of 1, 2, 3and 4are shown in Figure 3.All adsorbents 1, 2, 3and 4show peaks at the angle 2Өof 20º - 25º, due to the presence of SiO2 which resemble to Si-O-Si structure ofcrystobalite. The peaks at the angle of 40º-45º show the presence of MgO, at 45-50 the presence of CaO, at 43-45 the presence of SrO and at 20-40 due to the presence of BaSiO3. CaSiO3 3.3185 2.005 SrSiO3 2.7084 1.810 BaSiO3 2.5154 1.601 2.804 0.00010470 2.0089 1808.0286 0.000945 2.0089 2215.3935 0.000834 2.0844 2385.2880 020052-4

  6. FIGURE 3.XRDdiffractogram of Mg-silicate, Ca-silicate, Sr-silicate, Ba-silicate. FFA analysis The FFA contents in CPO A, B, Cand Dwere determined byGas Chromatography. The chromatogram of all CPOs are very similar, and as a representativeis shown in Figure 4which is the chromatogram of CPO B. From the chromatogram, the all of the CPO show the presence of diglyceride (DG), triglyceride (TG) and FFA. The content of FFA in A, B, C and D are are 4.79%, 7.35%, 10.37% and 13.34%, respectively. The FFA appeared at retention time between 7 – 11 minutes. FIGURE4. Chromatogram of CPOB Adsorption of FFA from CPO, A, B, C and D. Figure 5 shows the adsorption of FFA from CPO,A, B, C and D using adsorbent 1, 2, 3 and 4. Adsorption of FFA from CPO A(FFA content 4.79% ) using adsorbents 1, 2, 3 and 4(variation weight of 0.5 g, 1.0 g and 1.5 g)shown in Figure 5a. It can be seen that theadsorption trend of all adsorbents are the more the adsorbents used to adsorb FFA from A, the more the FFA adsorbed. Adsorbent 2is the best adsorbent to adsorb FFA from A. With the weight of 0.5 g, 1.0 g and 1.5 g it can adsorb FFA about 83%, 89% and 95%, respectively. The second is shown by 020052-5

  7. 3 which adsorb about 80%, 88% and 92% using 0.5 g, 1.0 g and 1.5 g of A, respectively. The other two adsorbents 1 and 4 are very poor. They can only adsorbed FFA from Aabout 64% - 74% for 1 and about 61% - 72% for 4. In figure 5b, where FFA is adsorbed from B(FFA content 7.35% ) using adsorbents 1, 2, 3and4(variation weight of 0.5 g, 1.0 g and 1.5 g), 2 is still the best adsorbent, it can adsorb FFA from B about 72%, 81% and 88% using 0.5 g. 1.0 g and 1.5 g, of 2, respectively, while 3canonlyadsorb FFA from B about 57% using 0.5 g of 3, but the adsorption of 3 become higher up to 81% when its amount is doubled to1.0 g and, the adsortion of FFA become 88% using 1.5 g of 3. Again, 1 and 4 are quite poor adsorbents which can only adsorb 55% - 66% for 1, and 55 – 56% for 4 90 2 3 2 95 3 85 90 80 FFA adsorption (%) 85 FFA adsorption (%) 75 80 70 1 1 75 65 4 70 60 4 55 65 50 60 0.4 0.6 0.8 1 1.2 1.4 1.6 0.4 0.6 0.8 1 1.2 1.4 1.6 Adsorbent mass (g) Adsorbent mass (g) . a b 90 90 2 3 2 3 85 85 80 80 75 FFA adsorption (%) FFA adsorption (%) 1 75 70 4 70 65 1 60 65 4 55 60 50 55 45 50 40 35 45 0.4 0.6 0.8 1 1.2 1.4 1.6 0.4 0.6 0.8 1 1.2 1.4 1.6 Adsorbent mass (g) Adsorbent mass (g) c d F FIGURE 5 IGURE 5. Adsorption of FFA by 1, 2, 3 and 4 from CPO A, B, C and D Figure 5c shows the adsorption of FFA from C (with FFA content 10.37%) using adsorbents 1, 2, 3 and 4(with weightvariation of 0.5 g, 1.0 g and 1.5 g). It is seen that2 shows that it is still far better than the other three adsorbents. It can adsorb FFA from CPO C about 72%, 75% and 87% using 0.5 g, 1.0 g and 1.5 g of 2, respectively, while 1can adsorb 55% and 70% of FFA from C (for 0.5 g and 1.0 g of 1) and3 can only adsorb 52% and 62%, but when the amount of adsorbent is raised to 1.5 g, 3becomea better adsorbent than 1, where 3 can adsorb FFA from CPO C about 85% while 1 can only adsorb 71%. Finally, Figure 5d shows the adsorption of FFA from CPO D.(13.34%) where 2 using 0.5 g, 1.0 g and 1.5 g can adsorb FFA from CPO D as much as 70%, 77% and 85%, respectively, which is still the best of all adsorbents used in these experiments. 3is second best where it can 020052-6

  8. adsorbed FFA from CPO D as much as 65%, 73& and 84%, while 4 can reach adsorption of FFA from D about 80% using 1.0 g of adsorbent.The worst is shown by 1 where it can adsorb FFA from D only as much as 50% - 65%. Since all the adsorbents, 1, 2, 3 and 4 are nanoporous, none of the FFA molecules can enter the pore of the adsorbents, therefore it is possible between adsorbent metals and FFA polar-polar interactions are occurred. CONCLUSION Adsorbents 1, 2, 3 and 4 have been prepared and characterized by common methods, it was used to adsorb FFA from CPO with different concentration of FFA. 2 shows the best adsorbent among all adsorbents and it can adsorbed FFA from CPO A 83% - 95%, from CPO B 72% - 88%, from CPO C 73% – 85%. And from CPO D 70% - 85%. The second best adsorbent is 3 which can adsorb FFA from CPO A 80% -90%, CPO B 60% - 86%, from C 65% - 82% and from D 60% - 65%, while 1 and 4 are almost the same which adsorb FFA from CPO A 61% - 70%, from CPO B 54% - 62%, from CPO C 40% - 70% and from CPO D 50% - 70%. The interactions between the FFA and the adsorbents are predicted to be polar-polar. ACKNOWLEDGEMENT The author were gratefully thank to BPPS DIKTI for doctoral scholarship and PT. Vanadia Utama, Jakarta for SEM- EDX analysis. REFERENCES [1] Rianto, B. Overview of palm oil industry landscape in Indonesia. Price Water House Coopers. 2013 [2] Indonesian Palm Oil Association (GAPKI). 2015 [3] SNI 01-2901-2006 [4] Amzul, R. The role of palm oil industry in Indonesia economy and its export competitiveness. 2011 [5] Qadeer, R. A Study of the Adsorption of Phenol by Activated Carbon from Aqueous Solutions. Turk J Chem. 2002 [6] Clowutimon, W., Kitchaiya, P., Assawasaengrat, P. Adsorption of Free Fatty Acid from Crude Palm Oil on Magnesium Silicate Derived from Rice Husk. Engineering Journal. Vol. 15, No. 3. 2011 [7] Bangun, N., Sembiring, S.B., Putri, N.K., Karo Karo, J. Performance of M-silicate and M-polystyrene sulfonate in Extraction of Carotenoids from Crude Palm Oil. Procedia Chemistry. 2015 Doi: 10.1016/j.proche.2015.12.063 [8] Karo Karo, J.A., Sembiring, S.B., Bangun, N., Herawan, T. Adsorption and desorption carotenoids of raw palm oil using salt m-polystyrene sulfonate (m = Na, Mg, Ca, Sr and Ba). Journal of sciences and technology.Vol 7(12), 1925-1932; 2014. 020052-7

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