Indonesian Journal of Chemical Research http://ojs3.unpatti.ac.id/index.php/ijcr Indo. J. Chem. Res., 10(1), 8-13, 2022 DOI: 10.30598//ijcr. 8 Production Process of Large Pore Size Activated Carbon from Palm Kernel Shell using Sodium Chloride as An Activator Ahmad Nurdin 1*, Iriani2, Hamidah Harahap2, Aliyah Fahmi3 1Master’s Student of Chemical Engineering Program, Engineering Faculty, University of Sumatera Utara, Almamater Kampus Street, USU Medan – 20155, North Sumatera, Indonesia 2Chemical Engineering Program, Engineering Faculty, University of Sumatera Utara, Almamater Kampus Street, USU Medan – 20155, North Sumatera, Indonesia 3 Chemistry Program, Health Faculty, University of Efarina, Wismar Saragih Street No.1 Pematang Siantar, North Sumatera *Corresponding Author: nurdinsyschem@gmail.com. Received: March 2022 Received in revised: April 2022 Accepted: May 2022 Available online: May 2022 Abstract This study aimed to determine the yield of activated carbon, iodine number, and surface area of palm activated carbon. Samples were produced by using sodium chloride (NaCl) as an activator. Palm shells that had been produced by the milling process were then sieved with a 12 mesh sieve and soaked in 20 % NaCl solution. The sample solution was heated over a water bath at 70 oC and continued with the drying process at a constant temperature of 105 oC. The activated shells continued the pyrolysis process at temperatures of 300, 400, and 500 oC for 3 hours. The activated carbon obtained from the pyrolysis process was weighed and then washed using hot distilled water. The samples were dried in an oven at a temperature of 105 oC for 24 hours. The results were analyzed for iodine number using iodometric titration method, surface area using Brunauer- Emmett-Teller (BET) method, and pore structure using the Scanning Electron Microscope (SEM) method. The results showed the best yield was 38.13 % obtained at 20% NaCl and a temperature of 400 oC. The best iodine number was 767.745 mg/g and surface area was 6.790 m2/g, pore volume 4.377 cc/g with pore size 9.781 A. Keywords: Activated carbon, NaCl, SEM, Iodin number, BET INTRODUCTION Indonesia is the largest producer and exporter of palm oil in the world. Statically between 2009-2019, there was an increased area of oil palm plantations, with only 7.9 million hectares in 2009, increasing to 14.5 million hectares in 2019 (Badan Pusat Statistik, 2019). The increase in area and production of palm oil resulted in more waste being produced (Schleicher et al., 2019). One of the abundant solid residues of palm oil production is the palm kernel shell. Currently, palm kernel shells are still underutilized and disposed of by burning. The palm oil processing process produces solid waste similar to empty fruit bunches (EFB) ranging from 22-25% and oil palm shells ranging from 5-7% of the total weight of fresh fruit bunches (FFB). The solid waste produced has great potential due to its high carbon content of 49.79% (Edmund et al., 2014). In general, coconut shells are used as fuel in electric generators in palm oil processing plants. Oil palm shell is a biomass waste composed of 53.40% lignin, 6.92% cellulose, and 26.12% hemicellulose. From this composition, oil palm shells have a lower flash point and thermal reactivity than empty fruit bunches (FEB) (Baffour-Awuah et al., 2021). Oil palm shells have the characteristics of a porous particle surface, low sulfur content, high mechanical strength, various functional groups, and insoluble in water (Rashidi & Yusup, 2021). Based on these compositions and characteristics, activated charcoal is one of the products with high economic value that can be utilized from oil palm shells. Activated charcoal is a highly porous material widely used in the separation process, both in the purification of liquid waste and the separation of gas phases. According to Heidarinejad et al. (2020) activated charcoal is an adsorbent material with a high degree of porosity and surface area and is composed of 90% carbon. Activated carbon is the most popular adsorbent for adsorption because it has a high adsorption capacity (Tanasale et al., 2014). Activated charcoal is a form of charcoal that has been activated by using CO2 gas, water vapor, or chemicals so that the pore is open. Thus, its adsorption power increases against color and odor substances (Sekewael et al., 2015). The carbon structure of activated charcoal consists of main functional groups such as carbonyl, Ahmad Nurdin and Aliyah Fahmi Indo. J. Chem. Res., 10(1), 8-13, 2022 DOI: 10.30598//ijcr. 9 carboxyl, phenol, lactone, and quinone, responsible for the contaminant adsorption process. Activated charcoal also has the advantages of a simpler production process, resistance to corrosion (acid and alkali), and can be used as a supportive catalyst (Rambabu et al., 2015) Several studies have produced activated charcoal from oil palm shells, including Okoroigwe et al. (2013). Purification of Ubu river water using activated charcoal adsorbents from oil palm shells succeeded in reducing the content of iron compounds from 1.82 mg/l to 0.29 mg/l. Ulfah et al. (2017) reported a study on the recovery of β-carotene compounds from palm oil using activated charcoal from oil palm shells. The adsorption capacity of 14.32 mg/g was obtained with the number of β-carotene compounds recovered was 28-30%. Lee et al. (2021) reported that activated charcoal from oil palm shells could be used in the adsorption process of methylene blue compounds with an adsorption capacity of 16.92 mg/g. Tan et al. (2021) reported that activated charcoal from oil palm shells could be used as an adsorbent in the POME waste treatment process, with a color removal efficiency of 99.7% and COD of 85.0%. Before being used as activated charcoal, oil palm shells go through two stages, namely carbonization, and activation. This process aims to increase oil palm shell-activated charcoal's porosity and surface area (Andas et al., 2017). There are three activation processes for charcoal: chemical, physical, and chemical-physical combinations. The physical activation process is carried out under atmospheric pressure using gas O2, CO2, N2, and water vapor at a temperature of 800-1100 ᵒC (Heidarinejad et al., 2020). The physical activation process has weaknesses such as long activation time, the low adsorption capacity of the adsorbent, and high energy consumption. The chemical activation process or wet oxidation of activated charcoal raw materials will be mixed with an activating agent, and then the mixture is heated at a temperature of 400-900 ᵒC (Hidayu & Muda, 2016). The chemical activation process has advantages such as a larger surface area of the adsorbent, higher porosity, shorter activation time, and lower energy consumption. The activators that are generally used to make activated charcoal are H3PO4, KOH, ZnCl2, NaOH, and K2CO3. Several studies have been carried out on the process of making activated charcoal from oil palm shells with chemical activation methods. Hidayu & Muda (2016) reported research on the manufacture of activated charcoal using a ZnCl2 activator and obtained a yield of 44% with a BET surface area was 1.223 m2/g. In a different study, Andas et al. (2017) reported making activated charcoal using a KOH activator and obtained a yield of 8.93% with a BET surface area of 994.83 m2/g. Nicholas et al. (2018) reported the manufacture of palm shell-activated charcoal using the H3PO4 activator, and the BET surface area was 1,169 m2/g. In a study conducted by Rashidi & Yusup (2021), making activated charcoal from palm oil-petroleum coke shells using a K2CO3 activator reported a significant increase in BET surface area on activated charcoal 317.746 m2/g from oil palm shells of 1.84 m2/g. Each activator commonly used in the production of activated charcoal, especially from biomass waste, has its weaknesses. The H3PO4 activator in making activated charcoal from lingo-cellulosic material limits the tar that comes out of the charcoal material during the carbonization process, which affects forming activated charcoal pores (Deliyanni, 2019). ZnCl2 activator is a strong dehydrating agent that prevents tar formation during the process and increases the release of impurities. Still, residues from the ZnCl2 activator will harm the environment (Heidarinejad et al., 2020). When used in biomass waste, the KOH activator produces low yields than other activators (Dzigbor & Chimphango, 2019). One of the activators that can be an alternative in making activated charcoal from palm kernel shell biomass waste is NaCl. NaCl is non-toxic and environmentally friendly, inexpensive, has high thermal conductivity, and is easily available for use in small-scale production processes (Dzigbor & Chimphango, 2019; Maulina et al., 2020). Several studies have been carried out to produce activated charcoal from biomass waste using NaCl activator. Dolas et al. (2011) reported on the manufacture of activated charcoal from pistachio shells biomass waste. NaCl activator showed the best BET surface area of 703.3 m2/g compared to alkaline activator NaOH of 370.52 m2/g and acid activator HCl of 353.25 m2/g. In the study of making activated charcoal from biomass waste Acacia auriculeaformis reported by Kra et al. (2019), the NaCl activator produced the largest activated charcoal yield of 48.87% compared to the H3PO4 acid activator of 41.81%. BET surface area of the NaCl activator was 395.40 m2/g, and the iodine value was 380.71 mg/g. Dzigbor & Chimphango (2019) reported making activated charcoal from mango seed biomass waste using NaCl as an activator, the BET surface area of activated charcoal products was 415 m2/g. According to Zakaria et al. (2021) apart from the type of activator, the variable concentration of Ahmad Nurdin and Aliyah Fahmi Indo. J. Chem. Res., 10(1), 8-13, 2022 DOI: 10.30598//ijcr. 10 activator, pyrolysis temperature, and activation time affect the yield and surface characteristics of the activated charcoal produced. Oil palm shells have the potential to be developed as a precursor in the manufacture of activated charcoal. This study aims to examine the effect of the chemical activation method using NaCl activator on yield and characteristics of activated charcoal from oil palm shells. The variables used in this study were activator concentration, pyrolysis temperature, and activation time. Activated charcoal produced will be used as an adsorbent in absorbing iron and turbidity in the underground water purification process. This study produced palm kernel shell-activated carbon by chemical activation using NaCl as an activating agent. This study aims to produce activated carbon and investigate the effect of NaCl as an activating agent on the characteristic of activated carbon from palm kernel shells. The research variable was pyrolysis temperature. The activated carbon obtained was analyzed for iodine number, surface area using Brunauer-Emmett-Teller (BET) method and pore structure using Scanning Electron Microscope (SEM). METHODOLOGY Materials and Instrumentals The material palm kernel shell was obtained from PMKS PT. Bumi Sama Ganda – Kuala Simpang palm oil mill. Sodium Chloride (NaCl, Merck Millipore) was used as the chemical activator, sodium thiosulfate (Na2S2O3, Merck Millipore), and potassium iodine (Merck Millipore). Instruments used in the study included a vertical tubular reactor equipped with a panel system, a gas cylinder with a regulator, and a nitrogen hose connected to the pyrolysis reactor. Methods Pre-treatment of Palm Kernel Shell Palm Kernel Shell (PKS) was used as the precursor for the activated carbon. The PKS were washed using water several times to remove dust and dirt. PKS samples were sundried for two days. Then samples were dried in an oven at 800C to remove surface moisture. The dry sample was ground and sieved to the size of 12 mesh and placed in a closed container for further use. Preparation of Activated Carbon 30 g of raw PKS was mixed with 100 ml of 20% NaCl solution. Impregnation was done at 70 ᵒC for 3 hours, soaking at room temperature for 24 hours. After impregnation, samples were dried in an oven at a temperature of 105 ᵒC to obtain a constant weight. The dried samples were then carbonized at 300 ᵒC, 400 ᵒC, and 500 ᵒC for 3 hours. Meanwhile, the samples without activation directly carbonized after sieving into a size of 12 mesh with the same variation of temperatures. The resulting activated carbon was cleaned using hot water several times. The washed samples were dried in an oven at 100 ᵒC for 24 hours to remove internal moisture. Samples were weighed and stored in a closed container for further use and analysis. Data Analysis The dry sample was weighed, and the yield percentage was calculated using Equation 1. Yield % = 𝐹𝑖𝑛𝑎𝑙 𝑀𝑎𝑠𝑠 𝐼𝑛𝑖𝑡𝑖𝑎𝑙 𝑀𝑎𝑠𝑠 𝑥 100% (1) Where Final Mass = Mass of the product; Initial Mass = Mass of precursor used SEM analysis (Zeiss-Evo-50) was carried out to determine the surface morphology of NaCl-AC. Na2S2O3 volumetric titration method based on ASTM D4607 was used to determine the iodine number of NaCl-AC. The NaCl-AC's specific surface area was determined by Brunauer-Emmett-Teller (BET) method (Quanta-chrome Novawin version 11.0). RESULTS AND DISCUSSION Influence of pyrolysis temperature on yield of Activation carbon Pyrolysis temperature is related to activated carbon yield as seen in Figure 1. Figure 1, shows that the yield of activated carbon indicated decreased with an increase in pyrolysis temperature from 300 ᵒC to 500 ᵒC. In this study, the best yield of activated carbon was obtained at a pyrolysis temperature of 300 ᵒC (38.13%). This phenomenon occurs because the pyrolysis process causes the release of more volatile components as the process temperature increase. Figure 1 also shows that activated carbon yield before pyrolysis of NaCl activation gives slightly better results than without NaCl activation. The activating agent NaCl acts as dehydrating agent inhibiting tar formation, thereby increasing the carbon yield (Rodrfguez-Reinoso & Sepúlveda-Escribano, 2001) Ahmad Nurdin and Aliyah Fahmi Indo. J. Chem. Res., 10(1), 8-13, 2022 DOI: 10.30598//ijcr. 11 Figure1. Effect of activation temperature on yield Activated Carbon (AC) Influence of Activation Temperature The activation temperature of activated carbon yield is also related to the iodine number as seen in Figure 2. Figure 2. Effect of NaCl on iodine number Activated Carbon (AC) Figure 2 shows the iodine values of NaCl-AC, which are better than that of AC without chemical activation within the studied temperature range. In this study, the optimum iodine number of activated carbon was obtained at a pyrolysis temperature of 400 ᵒC with 767.745 mg/g. the increase in pyrolysis temperature and processing time will lead to a decrease in activated charcoal yield. According to Rodriguez-Reinoso (Rodrfguez- Reinoso & Sepúlveda-Escribano, 2001), the active agent attacks carbon and produces several hydrolysis reactions and causing enhance in the elasticity and swelling of the precursor particles, thus leaving a porous activated carbon when the active agent is removed with distilled water after pyrolysis. In this study, the increase in iodine number was not linear with increasing temperature. This finding is due to the destruction of the carbon surface due to high- temperature carbonization. Alkali and salt activators tend to produce activated carbon with maximum micro-porous at the carbonization temperature of less than 500 ᵒC (Maulina et al., 2020) BET Surface Area BET analysis was used to show the surface area of activated carbon. BET analysis shows different AC results without activation and AC using NaCl activation in this study. The result presented in Table 1 shows that AC with chemical activation using NaCl provides a larger surface area of 6.790 m2/g than AC without chemical activation of 5.861 m2/g. NaCl-AC also shows the highest pore volume 4.377 cc/g compare to AC without chemical activation 1.505 cc/g. This is because an activating agent has contributed to creating more new pores and enlarging existing pores. BET surface area parameter towards activated carbon with and without NaCl as activator is represented in the Table 1. Table1. BET Surface Area of Carbon Parameter AC-Without Chemical Activation NaCl- AC Surface area (m2/g) 5.861 6.790 Pore Volume (cc/g) 1.505 4.377 Pore Size (Å) 9.504 9.781 Morphological Analysis SEM investigated the surface morphology of AC nonchemical activation and NaCl-AC and the images are shown in Figure 3. Based on Figure 3(a), it can be observed that there was a smooth surface and a small proportion of pores on the particle surface. However, in figure 3(b) there is a lot of development of pores on the particle surface. The activation treatment aims to enlarge the adsorbent pores (Priyanto et al., 2021). This finding may have resulted from the intercalation of NaCl and the dehydration of volatile materials. 0 10 20 30 40 50 300 400 500 A c ti v a te d C a rb o n Y ie ld ( % ) Activation Temperature ºC NaCl-ACl Without chemical activation-AC 640 660 680 700 720 740 760 780 300 400 500 Id o in e N u m b e r (m g /g ) Activation Temperature ºC Without chemical activation-AC NaCl-AC Ahmad Nurdin and Aliyah Fahmi Indo. J. Chem. Res., 10(1), 8-13, 2022 DOI: 10.30598//ijcr. 12 Figure 3. SEM images of (a) AC-without chemical activation and (b) NaCl-AC CONCLUSION NaCl can be used as an activating agent to produce activated carbon from palm shells (PKS). This study found the optimum temperature at 400 C with a yield of 38.13% and an iodine value of 767.75 mg/g. activated carbon using NaCl activation has a surface area of 6,791 m2/g and a pore volume of 4,377 cc/g with a pore size of 9,781 A. 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