ASCORBIC ACID ASSISTED MoSx IMMOBILISED ALGINATE HYDROGELS FOR REALISTIC ORGANIC POLLUTANT REMOVAL

The contamination of wastewater by synthetic dyes from industrial effluents remains a significant environmental concern, particularly at the low concentrations typical of real systems [1]. Molybdenum sulfide (MoSx) is a promising adsorbent due to its layered structure, high surface area, and abundance of active sites, such as defects or unsaturated sulfur species, that enable efficient pollutant removal [2]. This study aimed to develop a more sustainable synthesis route for MoSx using ascorbic acid as a green reducing agent and systematically investigate the effects of its concentration (0.3–0.5 M) and temperature (200–220 °C) on material properties and adsorption performance. Moreover, MoSₓ was incorporated into an alginate-based hydrogel to produce an easily processable adsorbent, and the adsorption performance of the resulting composite hydrogels for methylene blue removal was evaluated. The results demonstrate that ascorbic acid effectively enables MoSx formation, with higher concentrations yielding materials with greater surface area and improved adsorption capacity. The maximum methylene blue adsorption capacity reached 48.3 mg g-1, with 96.4% removal within 120 min. Immobilization in alginate hydrogels facilitated handling, separation, and reuse, while maintaining effective dye removal at low concentrations and showing improved performance upon reuse. Adsorption followed Langmuir and Temkin isotherm models. XPS analysis indicated that during adsorption methylene blue interacts primarily with COOH groups in the alginate matrix. Desorption studies revealed stronger dye retention in composite hydrogels compared to neat alginate. Overall, this work presents a sustainable and practical approach for efficient dye removal from realistic wastewater systems.