Understanding the relationship between the properties and performance of black titanium dioxide with core-shell structure (CSBT) for environmental remediation is crucial for improving its prospects in practical applications. In this study, CSBT was synthesized using a glycerol-assisted sol-gel approach. The effect of different water-to-glycerol ratios (W:G = 1:0, 9:1, 2:1, and 1:1) on the semiconducting and physicochemical properties of CSBT was investigated. The effectiveness of CSBT in removing phenolic compounds (PHCs) from real agro-industrial wastewater was studied. The CSBT synthesized with a W:G ratio of 9:1 has optimized properties for enhanced removal of PHCs. It has a distinct core-shell structure and an appropriate amount of Ti3+ cations (11.18), which play a crucial role in enhancing the performance of CSBT. When exposed to visible light, the CSBT performed better: 48.30 of PHCs were removed after 180 min, compared to only 21.95 for TiO2 without core-shell structure. The CSBT consumed only 45.5235 kWh/m3 of electrical energy per order of magnitude and cost 2.4127 per unit volume of treated agro-industrial wastewater. Under the conditions tested, the CSBT demonstrated exceptional stability and reusability. The CSBT showed promising results in the treatment of phenols-containing agro-industrial wastewater. Figure not available: see fulltext. © 2023, Higher Education Press.