Interfacial engineering of GQD/TiO₂-embedded photocatalytic concrete for visible-light-driven wastewater treatment:...

This study presents the design and evaluation of graphene quantum dots (GT) titania embedded in cementitious concrete (GQD/TiO₂-loaded concrete, GTC) for visible-light-driven photocatalytic decolorization of Reactive Black 5 (RB5), integrating experimental characterization with machine learning (ML) modeling. GT photocatalysts produced using the sol-gel approach outperformed bare TiO₂ in terms of visible-light activity. The 1 mol% GT calcined at 300 °C achieved approximately 100% RB5 elimination within 80 minutes. Embedding GT in concrete efficiently immobilized the photocatalyst while retaining high efficiency (89.7%), proving structural stability and reusability over numerous cycles. X-ray photoelectron spectroscopy (XPS) verified Ti-O-C interfacial bonding and surface -OH enrichment, whereas photoluminescence quenching revealed reduced electron-hole recombination. Radical scavenging experiments identified ˙O₂ ^- and ˙OH as dominant reactive species. High-performance liquid chromatography (HPLC) and chemical oxygen demand (COD) analyses confirmed the cleavage of chromophoric and aromatic structures into low-molecular-weight intermediates, achieving substantial mineralization and outperforming conventional TiO₂ systems. Ten supervised and deep learning machine learning models were developed to capture complicated, nonlinear behavior, with CatBoost and convolutional neural networks (CNN) outperforming others in terms of predicting accuracy. The key regulating elements, according to feature importance analysis, are reaction time and GTC dosage, followed by initial dye concentration. The integrated experimental-ML framework offers a scalable and interpretable strategy to develop photocatalytic concrete systems, allowing for predictive design and effective wastewater treatment. This study develops an approach for long-lasting, high-performance photocatalytic concrete, integrating mechanistic knowledge with data-driven optimization to provide long-term environmental cleanup.