Efficient Photocatalytic Degradation of Ibuprofen from Aquatic Waste Using a Microwave Synthesized MoS2@Cs3Bi2Br9 Nanocomposite

The persistent presence of pharmaceutical contaminants such as ibuprofen (IBF) in aquatic ecosystems poses significant environmental and health risks, as conventional wastewater treatments often fail to eliminate these recalcitrant compounds. Herein, a novel MoS₂@Cs₃Bi₂Br₉ heterojunction photocatalyst was synthesized via sol-gel and microwave methods to address this challenge. Comprehensive characterization (XRD, FTIR, SEM, EDX, and UV-vis) confirmed the structure of composite and optical properties, revealing a reduced bandgap of 3.04 eV (vs pristine Cs₃Bi₂Br₉) due to a type II heterojunction with staggered band alignment. This configuration enabled efficient charge separation, as photogenerated electrons migrated from the conduction band (CB) of Cs₃Bi₂Br₉ to MoS₂ (-0.3 eV), while holes transferred inversely, suppressing recombination and enhancing the redox activity. Under optimized conditions (20 mg/L IBF, pH 6.0, visible light, 0.1% H₂O₂), the 5% MoS₂@Cs₃Bi₂Br₉ composite achieved 96.77% degradation efficiency within 3 h, outperforming individual catalysts (61% for MoS₂-sol-gel, 76% for MoS₂-microwave, and 69% for Cs₃Bi₂Br₉). The staggered energy bands of the heterojunction facilitate electron transfer from Cs₃Bi₂Br₉ to MoS₂ and hole migration in the reverse direction, suppressing recombination and amplifying hydroxyl radical (•OH) generation. Low-dose H₂O₂ (0.1%) acted as an electron scavenger to boost •OH production, while excess H₂O₂ (1%) promoted recombination, reducing the efficiency. The composite exhibited exceptional reusability, retaining >90% activity over five cycles via H₂O₂-assisted regeneration. This work underscores the potential of MoS₂@Cs₃Bi₂Br₉ as a sustainable, high-performance photocatalyst for degrading pharmaceutical pollutants, offering a viable strategy to mitigate emerging contaminants in water systems.