Photocatalytic Degradation of Brilliant Blue Dye Under Solar Light Irradiation: An Insight Into Mechanistic, Kinetics, Mineralization and Scavenging Studies.

Brilliant blue dye (BB) is being extensively used in textile and cosmetic industries. It has been reported to cause cancer and asthma. In this study, ZnO and Bi-ZnO were synthesized by sol-gel method. The catalysts were characterized by XRD, SEM, FTIR, EDX, and BET. Both ZnO and Bi-ZnO were used for the photocatalytic degradation of BB under solar light irradiation. Different parameters, affecting the photocatalytic degradation of BB, like contact time, dye concentration, catalyst concentration, and pH were evaluated and optimized. The band gap for ZnO and Bi-ZnO was found to be 3.10 and 2.95 eV, respectively. Surface area and pore size for ZnO and Bi-ZnO were determined to be 104.03 m²/g and 199 nm, and 114.67 m²/g and 203 nm, respectively. The photocatalytic degradation of BB followed pseudo-first-order kinetics (R² = 0.9933). The value of first order rate constant (k₁) was found to be 3.14 × 10^-3 min^-1. Scavenging studies indicated that superoxide radicals (^•O₂^-) and hydroxyl radicals (^•OH) are mainly responsible for the degradation of BB. Both catalysts degraded BB efficiently but Bi-ZnO displayed better degradation potential (maximum 92%) than ZnO (maximum 76%). Finally, the current field challenges, recommendations and concluding remarks are presented.