Bismuth titanate based photocatalysts for degradation of persistent organic compounds in wastewater: A comprehensive review on synthesis methods, performance as photocatalyst and challenges

Bismuth-based nanocomposites have tremendous applications in wastewater treatment and air purification. Various bismuth-based nanocomposites have been developed and investigated, out of which, bismuth titanates have been explored a lot for their environmental applications. They are aurivillus type of compounds belonging to the family of layered perovskites. Bismuth titanates and their nanocomposites possess the ability to degrade persistent organic pollutants, present in water and wastewater, including various dyes (rhodamine blue, methyl orange, congo red, methylene blue, malachite green, brilliant red, acid orange, acid blue), organic compounds (phenol, methanol, formic acid, salicylic acid, p –chlorophenol), pharmaceutical compounds (sulpha methoxazole, ciprofloxacin, tetracycline, carbamazepine, gatifloaxin, 17β-Estradiol) etc. In this review, the various synthesis methods of bismuth titanates are discussed. This work reviews characterization and applications of Bi2Ti2O7, Bi4Ti3O12, Bi2Ti4O11, Bi8Ti4O14, Bi20TiO32 etc. For environmental remediation. Usage of these nanomaterials are in the form of slurry or immobilized system. However, future perspectives involving more research related to the development of novel bismuth-based nanocomposite materials with superior photocatalytic properties, easy recoverability, and practicability for real systems. Further, challenges related to fabrication of pure bismuth titanates, morphology and development of bismuth titanate photocatalyst are also stated. Some novel bismuth titanate nanocomposite photocatalysts including fiber-based photocatalyst, photocatalytic membrane, floating photocatalyst etc. are also discussed.