Comparative Adsorption of Methylene Blue Dye on Hexane-Washed and Xanthated Spent Grated Coconut (Cocos nucifera L.): Isotherms, Thermodynamics and Mechanisms
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Faculty of Applied Sciences, Universiti Teknologi Mara, 96400 Mukah, Sarawak, Malaysia
Faculty of Applied Sciences, Uitm Cawangan Pahang, Lintasan Semarak, 26400, Jengka Pahang, Malaysia
Department of Chemistry, College of Science, Ibb University, Ibb, Yemen
Department of Biosciences, Faculty of Science, Universiti Teknologi Malaysia, 81310 Johor, Malaysia
Faculty of Pharmacy and Health Sciences, Royal College of Medicine Perak, Universiti Kuala Lumpur, 30450 Ipoh, Perak, Malaysia
Megat Ahmad Kamal Hanafiah   

Faculty of Applied Sciences, Universiti Teknologi MARA, 26400 Jengka, Pahang, Malaysia
J. Ecol. Eng. 2022; 23(3):1–11
A batch system investigated the application of two types of chemically modified biosorbents derived from spent grated coconut (Cocos nucifera) powder to adsorb methylene blue (MB) from aqueous solutions. The biosorbents were characterised by spectroscopic and quantitative analyses. The assessment of MB adsorption onto the investigated biosorbents was studied at different experimental conditions with different pHs (2–9) and different initial concentrations of MB (10–400 mg/L) at three different temperatures (298, 308, and 318 K). The maximum adsorption capacity (qmax) of xanthated spent grated coconut (XSGC) was higher than that of hexane-washed spent grated coconut (HSGC). The thermodynamic study indicated that the MB adsorption process was spontaneous for both biosorbents. Desorption of MB-loaded biosorbents was carried out using HCl, NaOH, and Na2EDTA solutions. A desorption ratio of more than 90% was obtained over three adsorption/desorption cycles for HSGC. However, XSGC demonstrated poor MB desorption, implying a stronger MB interaction with XSGC, which could be attributed to H-bonding, Yoshida H-bonding, n-π, and π-π bonding. The study showed that HSGC and XSGC could be applied as biosorbents to remove low MB concentrations from aqueous solutions.