Indones. J. Chem., 2020, 20 (4), 842 - 849 Widiyastuti Widiyastuti et al. 842 Carbonization of Lignin Extracted from Liquid Waste of Coconut Coir Delignification Widiyastuti Widiyastuti 1,* , Mahardika Fahrudin Rois 1 , Heru Setyawan 1 , Siti Machmudah 1 , and Diky Anggoro 2 1 Department of Chemical Engineering, Institut Teknologi Sepuluh Nopember, Kampus ITS Sukolilo, Surabaya 60111, Indonesia 2 Department of Physics, Institut Teknologi Sepuluh Nopember, Kampus ITS Sukolilo, Surabaya 60111, Indonesia * Corresponding author: tel: +62-31-5946240 email: widi@chem-eng.its.ac.id Received: June 10, 2019 Accepted: October 14, 2019 DOI: 10.22146/ijc.46484 Abstract: Lignin, as a by-product of the pulping process, is less widely used for worth materials. In this study, the utilization of lignin by-product of the soda delignification process of coconut coir converted to the activated carbon by a simple precipitation method followed by the carbonization at various temperatures is presented. The by-product liquor of the soda delignification process having a pH of 13.4 was neutralized by dropping of hydrochloric acid solution to achieve the pH solution of 4, resulting in the lignin precipitation. The precipitated was washed, filtered, and dried. The dried lignin was then carbonized under a nitrogen atmosphere at various temperatures of 500, 700, and 900 °C. The dried lignin and carbonized samples were characterized using SEM, XRD, FTIR, and nitrogen adsorption-desorption analyzer, to examine their morphology, X-Ray diffraction pattern, chemical bonding interaction, and surface area-pore size distribution, respectively. The characterization results showed that the functional groups of lignin mostly disappeared gradually with the increase of temperature approached the graphite spectrum. The XRD patterns confirmed that the carbonized lignin particles were amorphous and assigned as graphitic. All samples had a pore size of 3–4 nm classified as mesoporous particles. This study has shown that the carbonization lignin at a temperature of 700 °C had the highest surface area (i.e., 642.5 m 2 /g) in which corresponds to the highest specific capacitance (i.e., 28.84 F/g). Keywords: coconut coir; soda delignification; lignin; carbonization; mesoporous particles ■ INTRODUCTION Lignin is the most abundant renewable source of aromatic groups in nature and the second most abundant terrestrial biopolymer after cellulose. The pulp and paper industry is the primary producer of cellulose-rich fibers. Besides, cellulosic ethanol facilities are currently coming to resolve the limitation of fossil fuel. Both industries produce lignin as a by-product. The processes of Kraft, sulfite, soda, organosolv, and hydrothermal are some of the delignification methods that use sodium hydroxide and sodium sulfide, sulfur dioxide, sodium hydroxide, an organic solvent, and highly compressed water and temperature, respectively, to separate cellulose fiber by dissolving the lignin. For non-woody lignocellulose sources, soda pulping is widely used for the delignification method [1]. On the other hand, the lignin market is still limited for the valuable application [2]. Therefore, the conversion of lignin to the more valuable functional materials is still a challenge, even though lignin is becoming promising for many future applications [3-5]. As the by-product, lignin liquor is usually treated as liquid wastewater, and then it is concentrated and fired to serve only as fuel producing steam, electricity, and inorganic chemical for internal mill use [6]. Several efforts for extracting lignin from black liquor before further processing are membrane-assisted electrochemical [7] and precipitation through the addition of an acidifying agent of carbon dioxide [8], chloric acid [9], and sulfuric acid [10]. Carbon black is mostly produced from incomplete combustion of fossil fuel. The utilization of agricultural