Enhanced Methylene Blue Decontamination Using (Alhagi graecorum) Root Biosorbent: Optimization and Adsorption Mechanisms

Abstract

Industrial dye pollution poses severe environmental and health risks due to the carcinogenicity of compounds like methylene blue (MB). This study introduces Alhagi graecorum roots, a novel, low-cost biosorbent sourced from the Libyan Sahara, for efficient MB removal from wastewater. Batch adsorption experiments optimized key parameters: pH (3–13), contact time (5–120 min), and temperature (35–55°C). Maximum adsorption capacity (101.01 mg/g) was achieved at pH 11, 35°C, and equilibrium time of 110 min, using 0.02 g of adsorbent (particle size: <125 μm). Kinetic analysis revealed that adsorption followed the pseudo-second-order model (R² = 0.987), indicating chemisorption dominance. Thermodynamic studies confirmed exothermic behavior, with capacity decreasing from 85.09 to 58.68 mg/g as temperature increased. Intraparticle diffusion modeling (R² = 0.995) demonstrated that MB uptake involved surface diffusion but was not the sole rate-limiting step. The biosorbent’s high efficiency, sustainability, and simplicity highlight its potential for scalable wastewater treatment, offering a green alternative to costly conventional methods.