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

• Foams were produced via mild alkali activation (KOH < 3 mol/L) of waste fraction of sodalime glass and volcanic ash • Magnetic Fe 3 O 4 nanoparticles covered by a SiO 2 layer are added to enhance foam functionality. • The introduction of Fe 3 O 4 @SiO 2 enhance both the absorption and the photocatalytic behavior of the foams. • 5 wt% of Fe 3 O 4 @SiO 2 nanoparticles yield optimal balance between porosity and adsorption capability. 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 TiO 2 and Fe 2 O 3 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.