Indones. J. Chem., 2022, 22 (1), 192 - 204 Novie Juleanti et al. 192 Comparison of the Adsorption Ability of MgAl-HC, CaAl-HC, and ZaAl-HC Composite Materials Based on Duku Peel Hydrochar in Adsorption of Direct Green Anionic Dyes Novie Juleanti 1 , Normah Normah 1 , Patimah Mega Syah Bahar Nur Siregar 1 , Alfan Wijaya 1 , Neza Rahayu Palapa 2 , Tarmizi Taher 3,4 , Nurlisa Hidayati 4 , Risfidian Mohadi 4 , and Aldes Lesbani 2,4* 1 Magister Program, Faculty of Mathematics and Natural Sciences, Sriwijaya University, Jl. Padang Selasa No. 524, Ilir Barat 1, Palembang 30139, South Sumatra, Indonesia 2 Graduate School, Faculty of Mathematics and Natural Sciences, Sriwijaya University, Jl. Palembang-Prabumulih Km. 90-32, Ogan Ilir 30862, South Sumatra, Indonesia 3 Department of Environmental Engineering, Faculty of Mathematics and Natural Sciences, Institut Teknologi Sumatera, Jl. Terusan Ryacudu, Way Hui, Jati Agung, Lampung 35365, Indonesia 4 Research Center of Inorganic Materials and Complexes, Faculty of Mathematics and Natural Sciences, Sriwijaya University, Jl. Padang Selasa, Bukit Besar, Palembang 30139, South Sumatera, Indonesia * Corresponding author: email: aldeslesbani@pps.unsri.ac.id Received: August 27, 2021 Accepted: November 14, 2021 DOI: 10.22146/ijc.68719 Abstract: Preparation of composite material from layered double hydroxide (LDH) with hydrochar (HC) from duku peel produces CaAl-HC, MgAl-HC, and ZnAl-HC have shown the success of the preparation process as evidenced by characterizations such as XRD and FT-IR. The XRD characterization data evidenced the typical diffraction of the hydrochar around 2θ = 20° in the composite material. FTIR analysis is a characterization that supports the success of composite materials, which showed the presence of typical vibrations of HC at 3245, 2931, and 1635 cm –1 contained in the composite spectrum. The application of MgAl-HC, CaAl-HC, and ZnAl-HC composites as adsorbents showed Q max (adsorption ability) values of 94.340 mg/g, 128.205 mg/g, and 89.286 mg/g. Overall the adsorption process is endothermic with a positive enthalpy value, and a negative Gibbs free energy value indicates a spontaneous adsorption process. The isotherm model of MgAl-HC, CaAl-HC, and ZnAl-HC show that the Langmuir isotherm model is more dominant, as indicated by the R 2 value closer to 1 which indicates that the adsorption process takes place in a monolayer. Keywords: duku peel; hydrochar; adsorption; regeneration; dyes ■ INTRODUCTION Lately, synthetic dyes have been in great demand in textiles, printing, paper, food, and pharmaceuticals. Synthetic dyes consist of cationic and anionic dyes, but most industries prefer the use of anionic dyes. Synthetic dyes are widely used as a substitute for natural dyes, which are unstable, and quickly decompose under sunlight, and the storage process must be precise. Synthetic dyes are the right choice because they are stable, do not break down quickly, and have many color variations [1]. Some of the advantages obtained from dyes can lead to uncontrolled use. Excessive use of dyes will harm the environment. Synthetic textile dyes have a complex aromatic molecular structure that makes them difficult to break down when disposed of in the ecosystem [2], which makes necessary efforts to overcome these harmful effects. Many methods can be used, such as ion exchange [3], biodegradation [4], chemical coagulation [5], catalytic reduction [6], and adsorption [7]. According to Milagres et al., adsorption is the most promising method for dealing with contamination, with an economic value, easy to do, and very efficient, making adsorption the suitable method for dealing with contamination [8]. Adsorption is an effective and