Design and evaluation of a novel pyridine-thiazole hybrid adsorbent as high-capacity adsorbent for methylene blue removal from water

This study explores the novel application of a pyridine-thiazole hybrid adsorbent, MPHT 4, for the efficient removal of methylene blue (MB) from contaminated water. The adsorbent was synthesized via a high-yield route and characterized using ¹H/¹³C NMR, IR spectroscopy, HRESI-MS, elemental analysis, SEM, and BET surface area measurements. SEM revealed a homogeneous morphology with low porosity, while BET analysis indicated a surface area of 68.83 m²/g and a total pore volume of 0.113 cm³/g, classifying the material as a Type IV isotherm with micropores. The adsorption efficiency of MPHT 4 was systematically evaluated, achieving 86.7% removal of 25 ppm MB at pH 7 with a dosage of 1.0 g/L within 60 min. Kinetic studies confirmed a pseudo-second-order mechanism, while equilibrium data best fit the Freundlich isotherm, indicating multilayer adsorption on a heterogeneous surface. Thermodynamic analysis revealed a spontaneous and exothermic process, supported by a negative ΔG° (- 18.39 kJ/mol) and a positive ΔH° (29.92 kJ/mol). The adsorbent exhibited excellent stability and reusability over six cycles, facilitated by electrostatic interactions between MB and the negatively charged surface (pHPZC = 7.8). These findings highlight MPHT 4 as a promising, high-capacity adsorbent for MB removal, combining structural robustness, optimal porosity, and efficient regeneration for practical wastewater treatment applications.