NaOH-Activated Carbon from Gnetum gnemon L. Shell Waste for Methylene Blue Adsorption from Aqueous Solutions

Lelifajri Lelifajri, Amiera Hafizhah, Khairi Khairi, Andriy Anta Kacaribu

Abstract

Synthetic dyes, such as methylene blue (MB), are widely used in textile and related industries, and their discharge into aquatic environments poses severe environmental and health risks due to their toxicity, persistence, and poor biodegradability. This study reports the preparation of activated carbon derived from melinjo (Gnetum gnemon L.) shell waste (MSAC) through carbonization at 300 °C for 1 h, followed by chemical activation using NaOH solutions (1–4 M) for 24 h. NaOH activation of G. gnemon shell carbon is introduced for the first time to enhance its surface characteristics and adsorption performance. Structural and surface modifications before and after activation were characterized by FTIR and SEM-EDX analyses. Batch adsorption experiments were performed to evaluate the effects of contact time, initial pH of MB, and dye concentration on MB removal. NaOH activation significantly improved the surface functionality and porosity of MSAC, resulting in a maximum adsorption capacity ( ) of 148.214 mg/g at pH 7.0 and an initial concentration of 200 ppm within 35 min. The adsorption process followed the Langmuir isotherm (R² = 0.963) and pseudo-second-order kinetics, indicating monolayer chemisorption on a homogeneous surface. These findings demonstrate that NaOH activation effectively enhances the adsorption performance of G. gnemon shell waste–based carbon, making it a low-cost, sustainable adsorbent for the treatment of dye-laden wastewater.

Keywords

References

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DOI: 10.14416/j.asep.2026.02.010

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