Magnetic alkali-activated foams from soda-lime glass and volcanic ash enabling efficient synergistic dye removal

As a solution to clean water scarcity, it is essential to develop new inexpensive and eco-friendly materials for wastewater treatment, since conventional methods are often energy-intensive, dependent on non-renewable and, in general, unsuitable for large-scale and sustainable applications. In this work, the preparation of magnetic foams via mild alkali activation (KOH, 3 M) process for water purification is reported. The process uses Mt. Etna volcanic ash and unemployed fraction of soda-lime glass obtained from purification of glass containers. Magnetic properties were imparted by the introduction of silica-coated magnetite nanoparticles at 5 % (m/m) and 10 % (m/m). The large surface area of the resulting foams makes them highly promising as adsorbent for dye removal. Additionally, the natural presence of TiO2 and Fe2O3 in the volcanic ash contributes to photocatalytic activity. Both adsorption and photocatalytic performance were evaluated using methylene blue aqueous solution (10 mg/ L) as model dye. An increased removal efficiency was observed following the incorporation of magnetite nanoparticles, reaching up to 96 %. These results highlight the potential of converting industrial and natural waste into functional materials for sustainable wastewater treatment applications.