Advancements in S-scheme photocatalytic material for wastewater treatment

In recent years, S-scheme photocatalytic treatment was used for removal of several pollutants from different industries to overcome the disadvantages of conventional photocatalytic treatment. This review provides an overview and comparison of degradation of various target pollutants like tetracycline (TC), ofloxacin (OFL), rhodamine B (RhB) and phenol using numerous S-scheme photocatalysts. Catalyst BiOBr (2.83 eV)/BiOAc1 −xBrx (3.28 eV) showed 99.2% removal efficiency for TC with 120 min when compared with other S-scheme photocatalyst. Higher catalyst dosage resulted in improved degradation rate of pollutant. For OFL, catalyst BiVO4 /CQDs/β-FeOOH exhibited highest efficiency of 99.21% with the lowest treatment time of 15 min which could be attributed due to peculiar molecular structure of Carbon Quantum Dots (CQDs) plate. Catalyst g-C3N4/Bi/BiVO4 achieved 100% removal efficiency for RhB within 70 min treatment time. Similarly for phenol, catalyst Bi7O9I3 /Cd0.5 Zn0.5S QDs/WO3 −x (BCW) achieved 100% removal efficiency within 60 min treatment time. The mechanism of degradation of pollutants can be communicated depending upon the position and type of reactive sites. Pollutants are degraded to various intermediates and subsequent mineralization by mechanisms like cleavage, dealkylation, etc. In addition to various operating conditions that affect the S-scheme photocatalysis like catalyst dosage, treatment duration, pollutant concentration, degradation pathway of various pollutants and the cost assessment of the S-scheme photocatalyst are discussed in detail.