Low-cost, high-stability aerogel for methylene blue dye adsorption

The escalating environmental burden caused by industrial wastewater has prompted increasing attention towards the development of green, cost-effective, and high-efficiency treatment technologies. In this study, a novel composite hydrogel adsorbent was rationally designed using the natural biopolymer sodium alginate (SA) as the matrix, crosslinked with low-cost agents – glutaraldehyde and polyethyleneimine (PEI) – and reinforced with montmorillonite (MMT), an inexpensive inorganic filler, to enhance structural integrity. The resulting SA-MMT-PEI hydrogel was successfully synthesised and employed for the adsorption of methylene blue (MB) dye. The material’s removal capacity for methylene blue (MB) dye was systematically evaluated, including both static adsorption and dynamic adsorption studies to simulate wastewater treatment. Under the optimal dynamic adsorption conditions, the maximum adsorption capacity reached 148.61 mg·g−1. Notably, this work introduced the concept of ‘unit-cost-based maximum adsorption capacity’ as a novel and comprehensive evaluation metric, integrating material performance and economic feasibility. The SA-MMT-PEI hydrogel demonstrated a value of 842.93 mg/$, markedly surpassing previously reported adsorbent materials. This metric provides a practical framework for the cross-comparative assessment of diverse adsorbents targeting identical pollutants, which highlights the application potential and economic viability of SA-MMT-PEI hydrogels for large-scale industrial wastewater treatment, offering insights for material selection and environmental engineering design.