Converting Durian Husk Into Adsorbent Beads for Methylene Blue Adsorption: Synthesis, Kinetics, Isotherms, and Reusability

ABSTRACT Environmental pollution from textile dyeing wastewater, particularly the discharge of harmful dyes like methylene blue (MB), poses a significant challenge. This study presents an innovative solution for dyeing wastewater treatment by utilizing durian husk, an agricultural waste, as an adsorbent for MB removal. The durian husk was converted into activated carbon through carbonization and activation and then incorporated into an adsorbent bead using a droplet microencapsulation method with alginate and calcium ions. The material was characterized using techniques like TGA, SEM/EDS, FT‐IR, and BET surface area analysis. Batch adsorption experiments were conducted with contact time conditions ranging from 2 to 48 h, initial MB concentrations ranging from 5 to 40 mg/L showed optimal performance under conditions of pH 7, 24‐h contact time, and 20‐mg/L MB concentration. The adsorption process was controlled by internal diffusion, following the Freundlich isotherm, and was exothermic and physical in nature; electrostatic interactions, hydrogen bonding, π–π interactions, functional group interactions, pore filling, and internal mass transfer mechanisms were predicted to be the contributing mechanisms for the adsorption of MB on AL–AC adsorbent. The adsorbent demonstrated excellent reusability, maintaining its efficiency after 10 cycles; the beads retained over 80% removal efficiency after 10 consecutive cycles. The initial cycle removal efficiency was 97.99% ± 0.11% and decreased to 80.39% ± 0.24% after the 10th cycle. This durian husk–based adsorbent offers a sustainable, cost‐effective solution for dye‐contaminated water treatment.