Design and development of a photochromic material based on spiropyran for Bisphenol A removal

A photochromic material including spiropyran (SP) and multi-walled carbon nanotubes (MWCNTs) was designed and evaluated as a catalyst for the removal of Bisphenol A (BPA) in aqueous solution. All photodegradation processes followed pseudo-first-order kinetics, with calculated rate constants (k) ranging from 0.0013 min − 1 in the absence of the catalyst to 0.0251 min − 1 in the presence of 1.00 g/L of the catalyst under simulated solar irradiation. The recycling experiments showed a gradual decrease in photocatalytic performance over four consecutive reaction cycles, suggesting a slight loss of catalyst activity during repeated use. XRD analysis showed that the overall crystalline structure of the catalyst remained essentially unchanged after four cycles compared with the fresh material. The photochromic properties of spiropyrans make them highly efficient molecules that are capable of producing Reactive Oxygen Species (ROS). The Electron Spin Resonance (ESR) experiments pointed to the efficient formation of 1 O 2 by the studied catalyst in aqueous suspension. The radical scavenging experiments indicated that both singlet oxygen ( 1 O₂) and hydroxyl radicals (•OH) play an important role in the BPA degradation process. In addition, the MCF-7 cell viability tests showed that the aqueous samples became less cytotoxic after photocatalytic treatment. Thus, it was demonstrated that the developed catalyst shows potential as a photocatalyst, particularly for the removal of micropollutants such as BPA from contaminated water.