Review: influence of synthesis methods and performance of rare earth doped TiO₂ photocatalysts in degrading dye effluents

In the era of rapid industrial growth, waste treatment becomes a critical issue. In this regard, titanium dioxide (TiO₂) photocatalysts doped with rare earth elements (Ce, Eu, and Er) have become the focus of research due to their potential for effective degradation of dye effluents. This review outlines the relationship between the synthesis methods used in the preparation of rare earth element-doped TiO₂ and its photocatalytic performance in degrading dye effluent. This comprehensive review considers the various synthesis approaches that have been developed, as well as their impact on the physicochemical properties and photocatalytic activity of TiO₂. The results of this analysis show that the selection of appropriate synthesis method, optimised doping value (0.1–2% molar), particle size, crystalline phase (anatase or rutile), as well as experimental conditions such as pH, light intensity, and initial dye concentration, significantly affect the degradation efficiency of TiO₂ photocatalysts. Methylene blue was degraded by 95% with Ce–TiO₂, 96% with Eu–TiO₂, and 100% with Er–TiO₂. Methylene orange was degraded by 87% with Ce–TiO₂, 98% with Eu-TiO₂, and 80% with Er–TiO₂. Rhodamine B was degraded by 93% with Ce–TiO₂, 100% with Eu–TiO₂, and 90% with Er–TiO₂. The implications of these findings for sustainable development in waste treatment, as well as future challenges and prospects, are also discussed to provide insights into the practical implementation and improvement of rare earth-doped TiO2 photocatalysts in real-world scenarios.