Graphitic carbon nitride/bismuth-based Z-scheme heterojunctions for the photocatalytic removal of pharmaceuticals and personal care products — a review

Z-scheme heterojunction in recent years is one of the most promising approaches in photocatalytic materials in solar light region for various environmental applications, including the removal of pharmaceuticals and personal care products (PPCPs). Integrating g-C₃N₄ and Bi-based semiconductors via Z-scheme is highly effective in providing efficient flow of charge carriers along with suitable redox sites. The g-C₃N₄/Bi-based photocatalysts were synthesized by hydrothermal, co-precipitation, co-calcination, solvothermal polycondensation, or ion exchange/photoreduction. Environmental pollutants, such as tetracycline, ofloxacin, ciprofloxacin, levofloxacin, cefixime, and carbamazepine, were degraded with efficiency exceeding 90%. The major reactive species identified in those Z-schemes were superoxide radicals, hydroxyl radicals, and electron-holes pair. Best processes revealed economically feasible with 700–800 kWh/m³ of electric energy per order (EEO). For solar light–driven processes, energy can be named as ‘free’ (sunlight), but EEO allows to compare new developments. In future studies, process economic aspect, effectiveness in case of real effluents, including high-salinity conditions and evaluation of photocatalysts stability, and metals leaching should be addressed.