Fabrication, functionalization and performance of doped photocatalysts for dye degradation and mineralization: a review

Textile wastewaters contain refractory dyes that cause pollution and socio-economic issues, thus calling for efficient remediation techniques such as photocatalysis. We review the fabrication, functionalization, performance and limitations of doped catalysts for degrading and mineralizing dyes. We present developments in photocatalyst immobilization and photocatalytic reactor design. Methods such as microwave irradiation, sonication and use of ionic liquids are emerging for the preparation of doped photocatalysts. Whilst single-dye systems have been extensively studied, there is limited knowledge on multiple-dye systems. Immobilization of photocatalysts is gaining popularity for large-scale application, but faces issues of erosion, corrosion, mechanical strength and structure integrity. Ecotoxicological studies are required in real environments to validate the potential applications of nanostructured doped photocatalysts.