38 Computational and Experimental Research in Materials and Renewable Energy (CERiMRE) Volume 3, Issue 1, page 38-46 Submitted : February 8, 2020 Accepted : April 20, 2020 Online : May 2, 2020 doi : 10.19184/cerimre.v3i1.26417 Study of Dielectric and Adsorption Properties of Activated Carbon Prepared from Water Hyacinth using KOH as an Activating Agent Mochammad Ghiffari 1,a , Wenny Maulina 1 , and Agung Tjahjo Nugroho 1 2 Departmen of Physics, Faculty of Mathematics and Natural Sciences, Universitas Jember, Jember 68121, East Java, Indonesia a arifary430@gmail.com Abstract. Activated carbon can be produced from the combustion of a materials containing carbon that has been activated using activator substances. In this paper, potassium hydroxide (KOH) was selected as an activating agent. The influence of KOH concentration was investigated to determine the dielectric and adsorption properties of activated carbon derived from water hyacinth. Drying water hyacinth was carbonize in the furnace at a temperature of 400°C followed by chemical activation with variation concentration of KOH solution that used are 25%, 30%, and 35% (w/v) respectively. The results show that the best activated carbon derived from water hyacinth was obtained using 35% (w/v) KOH solution as an activating agent with the dielectric constant is 4.04 while iodine number of 514.6 mg/g. Keywords: Water Hyacinth, Activated Carbon, KOH, Dielectric Constant, Iodine Number Introduction Indonesia is a country that has high biodiversity, but all of them have not been fully utilized. One of the biodiversity that is easily found is water hyacinth. Water hyacinth (Eichhornia crassipes), the aquatic biomass, has attracted significant attention due to its extremely rapid growth, presenting serious challenges in navigation, irrigation and power generation [1-2]. Water hyacinth has many benefits, one of which can be made into fertilizer for the growth of fluted pumpkin (Telfairia occidentalis) [3], the diets of sheep [4], biodegradable board [5], biomass briquette [6], and activated carbon for phosphate removal from wastewater [7]. Furthermore, water hyacinth is critical to be studied for its possibility as an alternative energy source [8]. For example, water hyacinth has been demonstrated to be useful to develop supercapasitors, for production ethanol and to improve the immune resistance of plants and animals [9]. Carbon materials are a black residue containing impure carbon produced from the process of burning materials containing carbon elements. Carbon materials can be produced from materials containing carbon by heating at high temperatures [10]. Activated carbon is a carbonaceous solid derived from coal or biomass via thermal or thermochemical processes [2]. In general, activated carbon can be divided into physical and chemical activation. Physical activation is a process of breaking carbon chains from organic compounds with the help of heat at temperatures of 800ºC to 900ºC [11]. Meanwhile, chemical activation is soaking charcoal with chemical compounds before heating [12]. The chemicals that are usually used for activation are CaCl2, MnCl2, KOH, Ca(OH)2, ZnCl2, NaOH, H3PO4, H2SO4, K2CO3, Na2CO3 [13]. Based on the fact that the activating agents potassium hydroxide (KOH) performed much better than the other activating agent in terms of its ability to produce very high surface area carbon. KOH was found to generate carbon with the highest porosity and surface area [14]. A number of studies mailto:aarifary430@gmail.com 39 Computational and Experimental Research in Materials and Renewable Energy (CERiMRE) Volume 3, Issue 1, page 38-46 Submitted : February 8, 2020 Accepted : April 20, 2020 Online : May 2, 2020 doi : 10.19184/cerimre.v3i1.26417 have been carried out to using KOH as an activating agent. Hwa-Young et al. synthesis of activated carbon from paper mill sludge by KOH-activation [15]. Yang et al. studied on the application of KOH to produce activated carbon to realize the utilization of distiller’s grains [16]. Pagketanang et al. investigated microporous activated carbon from KOH-activation of rubber seed-shells for application in capacitor electrode [17]. Jin-Young and Young-Seak measure electrochemical properties of KOH-activated lyocell-based carbon fibers for EDLCs [18]. The number of pores and large surface area correlate with the adsorption power of activated carbon [12]. In this study, iodine number was carried out to determine the adsorption capacity of activated carbon prepared from water hyacinth at various concentrations of KOH as an activating agent. Aside from iodine number, measurement of electrical properties of activated carbon was also carried out. The use of activated carbon as a raw material for electronic devices, such as batteries, has been widely carried out. Theoretical Background The use of carbon materials have been used for many applications, such as batteries, supercapacitors, gas sensors and dye-sensitized solar cells [19]. Over the years, the furnace has been used as a common heating method to manufacture carbon. In a furnace, heat is transferred through conduction and convection. The outer surface of the sample is in contact with the generated heat, which slowly diffuses inwards as a result of the thermal gradient between the surface and the core of the material’s particles [20]. Activated carbon refers to a wide range of carbonized materials of high degree of porosity and high surface area. Carbon structures contain the main functional groups such as carboxyl, carbonyl, phenol, lactone and quinone that are responsible for adsorbing contaminants. Oxygen, hydrogen, sulphur and nitrogen are also present in the form of functional groups or chemical atoms in the activated carbon structure. The unique adsorption properties depend on the existing functional groups of activated carbon, which are derived mainly from activation processes, precursors and thermal purification [21]. Potassium hydroxide (KOH) has been widely used as an activating agent in activated carbon preparation. During the activation process, the following reaction take place [20,22]: (1) (2) (3) Both mesopores and micropores are formed as a result of the intercalation of potassium into the carbon network during the activation. Besides, there is also a possibility for a secondary reaction to occur as follows: (4) 40 Computational and Experimental Research in Materials and Renewable Energy (CERiMRE) Volume 3, Issue 1, page 38-46 Submitted : February 8, 2020 Accepted : April 20, 2020 Online : May 2, 2020 doi : 10.19184/cerimre.v3i1.26417 The dielectric properties of the materials are very important in evaluating the penetration of energy that can be achieved [23]. The dielectric constant can be determined from the capacitance measurement, as follow [24]: (5) Where “C” is capacitance (F), “ ” is the dielectric constant, “ ” is permittivity of the vacuum (8.85 10 -12 C 2 /Nm 2 ), “A” is the area of the plates (m 2 ), and “d” is the plate separation (m). The product is called the permittivity of the medium and is denoted by , (6) For vacuum and . The dimensionless ratio: (7) Is called the dielectric constant of the substance. As remarked before, the dielectric constant can be calculated as bellow (8) Thus, the dielectric constant of a substance is the factor (>1) by which the capacitance increases from its vacuum value, when the dielectric is inserted fully between the plates of a capacitor. Adsorption capacity of activated carbon mainly depends on its porosity and surface area. Higher iodine numbers reflect better development of the microporous structure and higher adsorption abilities for low-molar-mass solutes [25]. The iodine sorption value (ISV) was calculated according to the Equation (6) bellow [26]: ( ) ( ) (9) where “ISV” is iodine sorption value (mg/g), “A” is volume of iodine solution (ml), “B” is volume of sodium thiosulfate (Na2S2O3) used (ml) “N(Na2S2O3)” is concentration of sodium thiosulfate (N), “N(iodine)” is concentration of iodine (N), “ ” is mass of activated carbon (g) and “ ” is dilution factor. Materials and Methods Preparation of water hyacinth activated carbon In this study, the stems of water hyacinth were used for the preparation of activated carbon. The stems of water hyacinth were cleaned, chopped into pieces and dried using oven for 24 h at 105°C until they become crispy. Then the dried stems of water hyacinth was grinded until it 41 Computational and Experimental Research in Materials and Renewable Energy (CERiMRE) Volume 3, Issue 1, page 38-46 Submitted : February 8, 2020 Accepted : April 20, 2020 Online : May 2, 2020 doi : 10.19184/cerimre.v3i1.26417 becomes powder. This powdered was heated up to 400°C in the furnace about 1 h to make relative charcoal. The water hyacinth charcoal was sieved to a mesh size of 200. To prepare activated carbon of water hyacinth, the charcoal was chemically activated using potassium hydroxide (KOH) as activating agent with concentration of 25%, 30%, and 35% (b/v), respectively. The process continued by heating and stirring using magnetic stirrer hotplate at 80°C for 4 h. The sample was filtrate and washed with chemical of 2 M HCl followed by distilled water to make the sample neutral and put in the oven again for 2 h at 100°C. After this process, the activated carbon derived from water hyacinth ready to use in measurement. Dielectric properties measurement Dielectric properties were measured using LCR meter Lutron 9183. The measurement of activated carbon derived from water hyacinth was carried out using a parallel plates capacitor. The activated carbon was poured in 31 mm × 31 mm × 4 mm rectangular planner moulds. The measurement procedure which is done by contacting the probe to a flat surface of sample, as shown in Figure 1. The experiment was measured capacitance at a frequency of 10 kHz. The dielectric constant was found by using equation (8). The measurement was repeated to all different concentration of potassium hydroxide (KOH) activator. Since the experimental variables are more in number it was planned to check the result and data through analysis of variance (ANOVA). ANOVA was used to estimate the statistical parameters. Figure 1. Set-up of dielectric properties measurement Determination of the iodine sorption value (ISV) A 5 g activated carbon derived from water hyacinth was mixture with a volume of 100 mL concentrated iodine solution (1 N). The mixture was allowed to stand for 15 minutes in order to reach sorption equilibrium between activated carbon and concentrated iodine solution. The aliquot amount of sample and iodine solution were titrated with 0.1 N sodium thiosulfate solution. The ISV was calculated according to the Equation (9). The measurement were conducted for each type of activated carbon. Results and Discussion Dielectric Properties Dielectric materials are characterized by their dielectric properties. Dielectric properties determine the ability of the material to absorb energy. The dielectric constant defines a measure of how much energy from an external electric field can be stored within a material through polarization mechanism [27-28]. The results in activated carbon electromagnetic constant are 42 Computational and Experimental Research in Materials and Renewable Energy (CERiMRE) Volume 3, Issue 1, page 38-46 Submitted : February 8, 2020 Accepted : April 20, 2020 Online : May 2, 2020 doi : 10.19184/cerimre.v3i1.26417 shown as Figure 2. From Figure 2 can be seen the dielectric constant of the activated carbon increased with increasing concentration of activating agent. The dielectric constant of the activated carbon derived from water hyacinth using concentration of KOH (25 wt%, 30 wt% and 35 wt%) are 2.78 ± 0.18, 2.82 ± 0.21, and 4.04 ± 0.29, respectively. The increase in the concentration of KOH causes the dielectric constant value will also increase. An increase the magnitude of dielectric constant is thought to be due to an increase in the surface area of activated carbon. The use of KOH as activating agent was found to generate carbon with the highest porosity and surface area [14]. These results were in agreement with those of Yuningsih et al. in the activation of corn cobs and coconut shell carbon with KOH where surface area or pores volume increased with increase in KOH concentration [29]; Tetra et al. who observed that the ability of activated carbon to store an electrical charge will increase as the surface area of activated carbon increases [30]. The experimental data and analysis were checked by one-way ANOVA to determine the effect of KOH concentration on the dielectric properties of activated carbon derived from water hyacinth. Based on the one-way ANOVA test, the results obtained Pvalue (Sig) <0.05, which means Ho is rejected, meaning that there is an effect of varying the concentration of KOH activator in the process of synthesizing activated carbon derived from water hyacinth to the value of the dielectric constant. Figure 2. The dielectric constant of activated carbon derived from water hyacinth using KOH as activating agent Iodine Sorption Value (ISV) The effects of varying the concentrations of the activating agent (KOH) on the iodine number of the chemically activated carbon derived from water hyacinth are shown in Figure 3. Figure 3 showed that the iodine number increased with increasing concentration of activator. The results 43 Computational and Experimental Research in Materials and Renewable Energy (CERiMRE) Volume 3, Issue 1, page 38-46 Submitted : February 8, 2020 Accepted : April 20, 2020 Online : May 2, 2020 doi : 10.19184/cerimre.v3i1.26417 of the iodine number of activated carbon derived from water hyacinth with a concentration of 35wt% KOH shows the highest iodine sorption value of 514.6 mg/g, while the concentration of 30wt% KOH was 477.8 mg/g and the lowest iodine number was with a concentration of 25wt% KOH of 409.5 mg/g. The increase in the iodine number was due to increase in pore formation and hence adsorptive capacity of the activated carbon as impregnation increased. The iodine number is defined as the milligrams of iodine adsorbed by one gram of carbon when the iodine residual concentration of the filtrate is 0.02N (0.01 mol/L) according to ASTM D4607 standard, which is based on a three- point isotherm. Hence it is a measure of the iodine adsorbed in the pores of the activated carbon and an indication of the pore volume available in the activated carbon. Therefore, the carbon should be activated at concentration that gives the highest iodine value [31]. Figure 3. Effect of concentration of KOH as activating agent on iodine number of activated carbon derived from water hyacinth Conclusions From this experiment, activated carbon derived from water hyacinth in various concentration KOH activator in term of the dielectric properties and iodine sorption value have been investigated. It has been seen that the increase concentration of KOH in the process of synthesizing activated carbon causes increasing the dielectric constant and iodine number. In addition, optimum activated carbon derived from water hyacinth was obtained when the value of the dielectric constant was minimum and the value of iodine number was maximum. The dielectric constant minimum when concentration of 25wt% KOH was 2.78 ± 0.18, meanwhile iodine number maximum when concentration of 35wt% KOH was 514.6 mg/g. Based on the results obtained, it is known that the dielectric properties and iodine sorption value from activated carbon can be used according to theirs application later. 44 Computational and Experimental Research in Materials and Renewable Energy (CERiMRE) Volume 3, Issue 1, page 38-46 Submitted : February 8, 2020 Accepted : April 20, 2020 Online : May 2, 2020 doi : 10.19184/cerimre.v3i1.26417 ACKNOWLEDGEMENTS We would like to express our gratitude to Hibah KeRis in 2020 from LP2M University of Jember for all the support provided. References [1] K.S. Ukanwa, K. Patchigolla, R. Sakrabani, E. Anthony and S. Mandavgane, 2019, A Review of Chemicals to Produce Activated Carbon from Agricaltural Waste Biomass, Sustainability, volume 11, page 1 – 35. [2] S. Sukarni, Y. Zakaria, S.Sumarli, R. Wulandari, A.A. Permanasari and M. Suhermanto, 2019, Physical and Chemical Properties of Water Hyacinth (Eichhornia crassipes) as a Sustainable Biofuel Feedstock, IOP Conf. Series: Materials Science and Engineering, volume 515, page 012070 – 012077. [3] K.O. Sanni and J.M. Adesina, 2011, Utilization of Water Hyacinth (Eichhornia crassipies Mart Solms) as Liquid Fertilizer on the Growth and Yield of Fluted Pumpkin (Telfairia occidentalis), South Asian Journal of Experimental Biology, volume 2, no. 1, page 33 – 37. [4] G.A. Vasconcelos, R.M.L. Veras, J.L. Silva, D.B. Cardoso, P.C. Soares, N.N.G. Morals and A.C. Souza, 2016, Effect of Water Hyacinth (Eichhornia crassipes) Hay Inclusion in The Diets of Sheep, Trop Anim Health Prod, volume 48, page 539 – 544. [5] W. Rahmawati, A. Haryanto and S. Suharyatun, 2018, Development of Biodegradable Board Using Water Hyacinth (Eichornia crassipes), International Journal of Environment, Agriculture and Biotechnology, volume 3, no. 1, page 170 – 174. [6] K. Munjeri, S. Ziuku, H. Maganga, B. Siachingoma, S. Ndlovu, 2016, On The Potential of Water Hyacinth as a Biomass Briquette for Heating Applications, International Journal of Energy and Environmental Engineering, volume 7, page 37 – 43. [7] S.M. Gawande, A.A. Mane and N.S. Belwalkar, 2017, Experimental Study of Activated Carbon Derived from Dried Water Hyacinth and Its Performance in Phosphate Removal from Wastewater, International Journal of Current Research, volume 9, no. 7, page 53514 – 53517. [8] W. Maulina, R. Kusumaningtyas, Z. Rachmawati, Supriyadi, A. Arkundato, L. Rohman and E. Purwandari, 2019, Carbonization Process of Water Hyacinth as an Alternative Renewable Energy Material for Biomass Cook Stoves Applications, IOP Conf. Series: Earth and Environmental Science, volume 239, page 012035 – 012042. [9] V.K. Guna, M. Ilangovan, A.M. Gangadharaiah and N. Reddy, 2017, Water Hyacinth: A Unique Source for Sustainable Materials and Products, ACS Sustainable Chemistry and Engineering, page 1 – 50. [10] I.M. Siaka, N.P.D. Febriyanti, E. Sahara, I.M.S. Negara, 2016, Pembuatan dan Karakterisasi Arang dari Batang Tanaman Gumitir (Tagetes erecta) Pada Berbagai Suhu 45 Computational and Experimental Research in Materials and Renewable Energy (CERiMRE) Volume 3, Issue 1, page 38-46 Submitted : February 8, 2020 Accepted : April 20, 2020 Online : May 2, 2020 doi : 10.19184/cerimre.v3i1.26417 dan Waktu Pirolisis, Cakra Kimia Indonesian E-Journal of Applied Chemistry, volume 4, no. 2, page 168 – 177. [11] F.F. Polii, 2017, Effects of Activation Temperature and Duration Time on the Quality of the Active Charcoal of Coconut Wood, Journal of Plantation Based Industry, volume 12, no. 2, page 21 – 28. [12] M. Lempang, 2014, Pembuatan dan Kegunaan Arang Aktif, Info Teknis EBONI, volume 11, no. 2, page 65 – 80. [13] A.H. Surest, J.A.F. Kasih and A. Wisanti, 2008, Pengaruh Suhu, Konsentrasi Zat Aktivator dan Waktu Aktivasi terhadap Daya Serap Karbon Aktif dari Tempurung Kemiri, Jurnal Teknik Kimia, volume 15, no. 2, page 17 – 22. [14] H. Xia, J. Wu, C. Srinivasakannan, J. Peng and L. Zhang, 2015, Effect of Activiting Agent on the Preparation of Bamboo-Based High Surface Area Activated Carbon by Microwave Heating, High Temperature Materials and Processes, volume 35, no. 6, page 1 – 7. [15] K. Hwa-Young, P. Sang-Sook and R. Yu-Sup, 2006, Preparation of Activated Carbon from Paper Mill Sludge by KOH-Activation, Korean Journal of Chemical and Engineering, volume 23, no. 6, page 948 – 953. [16] H.M. Yang, D.H. Zhang, Y. Chen, M.J. Ran and J.C. Gu, 2017, Study on The Application of KOH to Produce Activated Carbon to Realize The Utilization of Distiller’s Grains, IOP Conference Series: Earth and Environmental Science, volume 69, page 012051 – 012058. [17] T. Pagketanang, A. Artnaseaw, P. Wongwicha and M. Thabuot, 2015, Microporous Activated Carbon from KOH-Activation of Rubber Seed-Shells for Application in Capacitor Electrode, Energy Procedia, volume 79, page 651 – 656. [18] J. Jin-Young and L. Young-Seak, 2018, Electrochemical Properties of KOH-Activated Lyocell-Based Carbon Fibers for EDLCs, Carbon Letters, volume 27, page 112 – 116. [19] A. Wang and D.D.L. Chung, 2014, Dielectric and Electrical Conduction Behavior of Carbon Paste Electrochemical Electrodes, with Decoupling of Carbon, Electrolyte and Interface Contributions, Carbon, volume 72, page 135 – 151. [20] T.S. Hui and M.A.A. Zaini, 2015, Potassium Hydroxide Activation of Activated Carbon: A Commentary, Carbon Letters, volume 16, no. 4, page 275 – 280. [21] Z. Heidarinejad, M.H. Dehghani, M. Heidari, G. Javedan, I. Ali and M. Sillanpaa, 2020, Methods for Preparation and Activation of Activated carbon: A Review, Environmental Chemistry Letters, volume 18, page 393 – 415. [22] C.G. Joseph, H.F.M. Zain and S.F. Dek, 2006, Treatment of Landfill Leachate in Kayu Madang, Sabah: Textural and Physical Characterization (Part 1), Malaysia Journal of Analytical Sciences, volume 10, no. 1, page 1 – 6. 46 Computational and Experimental Research in Materials and Renewable Energy (CERiMRE) Volume 3, Issue 1, page 38-46 Submitted : February 8, 2020 Accepted : April 20, 2020 Online : May 2, 2020 doi : 10.19184/cerimre.v3i1.26417 [23] S.O. Nelson, 1999, Dielectric Properties Measurement Techniques and Applications, American Society of Agricultural Engineers, volume 42, no.2, page 523 – 529. [24] T.T. Grove, M.F. Masters and R.E. Miers, 2005, Determining Dielectric Constants Using a Parallel Plate Capacitor, American journal of Physics, volume 73, no. 1, page 52– 56. [25] M.A. Bedmohata, A.R. Chaudhari, S.P. Singh and M.D. Choudhary, 2015, Adsorption Capacity of Activated Carbon Prepared by Chemical Activation of Lignin for The Removal of Methylene Blue Dye, International Journal of Advanced Research in Chemical Science, volume 2, no. 8, page 1 – 13. [26] L.E. Laos and A. Selan, 2016, Pemanfaatan Kulit Singkong sebagai Bahan Baku Karbon Aktif, Jurnal Ilmu Pendidikan Fisika, volume 1, no. 1, page 32 – 36. [27] S.N. Ab Jabal, Y.B. Seok and W.F. Hoon, 2016, Carbon Composition, Surface Porosities and Dielectric Properties of Coconut Shell Powder and Coconut Shell Activated Carbon Composites, ARPN Journal of Engineering and Applied Sciences, volume 11, no. 6, page 3832 – 3837. [28] N. Alias, M.J. Kamaruddin and M.A.A. Zaini, 2017, Dielectric Properties of Sodium Hydroxide-Impregnated and Activated Cempedak Peel Samples at Microwave Frequencies, Chemical Engineering Transactions, volume 56, page 931 – 936. [29] L.M. Yuningsih, D. Mulyadi and A.J. Kurnia, 2016, Pengaruh Aktivasi Arang Aktif dari Tongkol Jagung dan Tempurung Kelapa terhadap Luas Permukaan dan Daya Jerap iodin, Jurnal Kimia VALENSI: Jurnal Penelitian dan Pengembangan Ilmu Kimia, volume 2, no. 1, page 30 – 34. [30] O.N. Tetra, H. Aziz, Syukri, B. Arifin and A. Novia, 2018, The Effect of Addition of Activated Carbons from Peat on Performance of Supercapacitor Base of Activated Carbon of Palm Kernel Shell, Jurnal Zarah, volume 6, no. 2, page 47 – 52. [31] Akpa, J.G. Dagde and K. Kekpugile, 2018, Effect of Activation Method and Agent on the Characterization of Prewinkle Shell Activated Carbon, Chemical and Process Engineering Research, volume 56, page 24 – 36.