Facile metal organic framework composites as photocatalysts for lone simultaneous photodegradation of naproxen, ibuprofen and methyl orange

Pharmaceuticals and dyes are known to have endocrine disrupting effects in humans and aquatic animals. As a result of inefficient removal of these micropollutants from wastewater, they have been detected in potable water supplies. In this work, photocatalysts were prepared by incorporating TiO2 and ZnO into the framework of the MOF, MIL-53(Al), and were used in photodegradation studies of single and binary mixtures of naproxen, ibuprofen and methyl orange. The photocatalyst composites, MIL-53(Al)@TiO2 and MIL-53(Al)@ZnO, were characterized by XRD, FTIR, BET and FE-SEM, which confirmed attachment of TiO2 and ZnO nanoparticles to MIL-53(Al). DRS revealed direct optical band gaps of MIL-53(Al)@TiO2 and MIL-53(Al)@ZnO to be 3.34 eV and 3.24 eV, respectively. Uncoated MIL-53(Al) showed greatest photodegradation efficiency for naproxen (89.5%), closely followed by MIL-53(Al)@TiO2 (80.3%) and MIL-53(Al)@ZnO (76.6%). Uncoated MIL-53(Al) was also efficient at degrading ibuprofen from single and binary micropollutant systems, with MIL-53(Al)@ZnO performing better than MIL-53(A1)@TiO2 in both systems. MIL-53(Al)@ZnO was the only photocatalyst that was able to degrade methyl orange in both systems. It was established that a 3:1 ratio of naproxen (mg/L) to MIL-53(Al)@TiO2 (mg) was optimum for photodegradation, while for ibuprofen and methyl orange in single and binary systems, a 2:1 ratio of total micropollutant (mg/L) to MIL-53(Al)@ZnO (mg) gave the best degradation performance. The photodegradations kinetics were investigated and fitted to zero and pseudo-first/second order models. Recyclability of MIL-53(Al)@TiO2 for three consecutive photodegradation cycles showed a decrease of only 13.6% in photodegradation efficiency. Experiments conducted with scavengers showed that hydroxyl radicals played a major role in the photocatalytic process photodegradation, and it was found that only 1 h of treatment was sufficient to obtain a considerable COD reduction of 58%. This study provides a promising strategy for uniform MOF loading into ZnO and TiO2 for binary pharmaceutical and dye wastewater photodegradation treatment. (C) 2022 The Author(s). Published by Elsevier B.V.

Automated summary

Pharmaceuticals and dyes are known to have endocrine disrupting effects and can contaminate water supplies. By incorporating TiO2 and ZnO nanoparticles into MOF material MIL-53(Al), effective photocatalysts were developed for the degradation of these pollutants, showing high degradation efficiency and recyclability.