Red Mud as an Additive in the Extrusion of Protein-Based Porous Materials

Journal article, 2025

This study explores the dual challenge of enhancing the properties of protein-based foams produced from agricultural by-products through the incorporation of red mud waste from alumina production. Foams were manufactured using an extrusion process, employing gluten and zein proteins, with raw red mud and its oxalic acid leachates serving as additives. A factorial design was utilized to assess the significance of various parameters on the mechanical properties of materials. The results indicate that red mud-based additives do not improve foam mechanical stability in terms of stiffness (as measured by Young's modulus) and thus do not function effectively to form short crosslinking bridges. However, the results show red mud serves mainly as a plasticizer and reducing/oxidizing agent, while also potentially enhancing the formation of long crosslinking bridges. This is evidenced by a significant increase in foam strain when red mud powder is extruded with gluten, reaching 190% strain at break and densities between 500 and 1500 kg/m³. Consequently, red mud shows potential to be repurposed as an additive in protein-based foams, suitable for applications requiring elastic deformation while keeping a stable porous structure manufactured via continuous extrusion.