Photoreactive red mud cementitious composites for environmental remediation
This study explores the recycling of red mud (RM), an iron-rich and highly alkaline residue from the Bayer alumina refining process, as a partial substitute for cement and its valorisation as a low-cost multifunctional photocatalyst within cementitious composites. RM was incorporated as a partial ce...
| Autores: | , , , , |
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| Tipo de recurso: | artículo |
| Fecha de publicación: | 2026 |
| País: | España |
| Institución: | Universidad de Navarra |
| Repositorio: | Dadun. Depósito Académico Digital de la Universidad de Navarra |
| Idioma: | inglés |
| OAI Identifier: | oai:dadun.unav.edu:10171/120548 |
| Acceso en línea: | https://hdl.handle.net/10171/120548 |
| Access Level: | acceso abierto |
| Palabra clave: | Photocatalytic activity NOx abatement Fe2O3/TiO2 heterojunction Leaching Visible light irradiation Embodied CO2 emissions |
| Sumario: | This study explores the recycling of red mud (RM), an iron-rich and highly alkaline residue from the Bayer alumina refining process, as a partial substitute for cement and its valorisation as a low-cost multifunctional photocatalyst within cementitious composites. RM was incorporated as a partial cement substitute (≤15 wt%) in mortars in both oven-dried and thermally treated forms (300 ◦C and 600 ◦C), and its effect on hydration, workability, strength, microstructure, leaching behaviour, and embodied CO2 emissions was assessed. The photocatalytic activity of RM mortars was examined through nitrogen oxide (NOx) abatement under solar and visible light irradiation. The role of RM in modulating light absorption and its impact on the photocatalytic efficiency of titanium dioxide (TiO2)-coated mortars was also assessed. Regardless of RM type, partial substitution up to 10 % maintained early-age strength comparable to control mix, whereas higher replacement levels reduced long-term mechanical performance due to limited pozzolanic activity of RM and increased macroporosity of matrix. RM incorporation enhanced photocatalytic efficiency, achieving >8 % NOx removal, fulfilling Class 3 air-purification criteria. TiO2 coated RM samples showed 51 % higher visible-light NOx abatement than control, attributed to strong interactions between TiO2 and RM's hematite phase. Environmental safety was confirmed by >99 % immobilisation of trace elements and controlled alkali release. Moreover, 15 % RM substitution reduced CO2 emissions (~12 %), costs (~7 %), and life-cycle costs (~3.5 %), emphasising its dual environmental and economic advantages. Collectively, these findings highlight RM as a high-value additive that couples waste valorisation with photocatalytic air-pollution mitigation, offering a scalable route toward greener construction materials. |
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