The Key Role of Carbon Materials in the Biological and Photocatalytic Reduction of Nitrates for the Sustainable Management of Wastewaters Pastrana Martínez, Luisa María Morales Torres, Sergio Maldonado Hódar, Francisco José Biofilms activated carbon nanocarbons This work explores the influence of material properties and experimental conditions on both biological and photocatalytic nitrate reduction processes. For the biological route, results demonstrate that carbon supports, specifically carbon gels, with open porosity, slight acidity, and high purity enhance E. coli adhesion and promote the formation of highly active bacterial colonies. However, carbon supports of bacteria, produced from waste biomass, emerge as a sustainable and cost-effective alternative, improving scalability and environmental value. The complete conversion of nitrates to nitrites, followed by full nitrite reduction, is achieved under optimized conditions. Photocatalytic nitrate reduction under solar radiation is also proposed as a promising and ecofriendly upgrade method to conventional wastewater treatment. Graphene oxide (GO) was used to enhance the photocatalytic activity of TiO2 nanoparticles for the degradation of nitrates. The efficiency of nitrate reduction is found to be highly sensitive to solution pH and the physicochemical nature of the photocatalyst surface, which governs nitrate interactions through electrostatic forces. TiO2–GO composites achieved up to 80% nitrate removal within 1 h and complete removal of 50 mg/L nitrate within 15 min under optimized conditions. The screening of hole scavengers revealed that formic acid, in combination with the TiO2–GO composite, delivered exceptional performance, achieving complete nitrate reduction in just 15 min under batch conditions at an acidic pH. 2025-11-05T12:15:33Z 2025-11-05T12:15:33Z 2025-10-06 journal article Pastrana-Martínez, L.M.; Morales-Torres, S.; Maldonado-Hódar, F.J. The Key Role of Carbon Materials in the Biological and Photocatalytic Reduction of Nitrates for the Sustainable Management of Wastewaters. Catalysts 2025, 15, 958. https://doi.org/10.3390/catal15100958 https://hdl.handle.net/10481/107793 10.3390/catal15100958 eng http://creativecommons.org/licenses/by/4.0/ open access Atribución 4.0 Internacional MDPI