Novel photocatalytic textile floater made with Ce0.85Y0.1Mg0.05O2-δ for the high degradation of methylene blue and fomesafen (Flex) under solar light

• Methylene-blue (MB) and fomesafen (FLEX) were degraded using a PETbased floater • CeO 2 :Y,Mg (CeYMgO) powder degraded MB/FLEX with 98-100% efficiency under sunlight • Composite floater T+G+CeYMgO degraded MB and FLEX with 90-98% under sunlight • The MB degradation efficiency of CeYMgO decreased 2% after three cycles of reuse • The predominant oxidizing species were (• O 2 − ), followed by (h+) and (•OH) In this work, photocatalytic floaters were made using polyethylene terephthalate (PET)-based textiles (T), graphene and CeO 2 :Y,Mg (CeYMgO) photocatalyst powder. This last material had a cubic structure and consisted in porous particles with an average size of 460 nm. Firstly, CeYMgO powder was evaluated for degradation of methylene-blue (MB) under solar light and it produced a maximum degradation of 95.65% (at pH=7) after 180 min under sunlight. Next, the textile was coated with graphene to form the T+G photocatalytic floater. Later, the T+G floater was coated with CeYMgO powder to make the T+G+CeYMgO photocatalytic floater. The T+G and T+G+CeYMgO floaters produced maximum MB degradation percentages of 93.16% and 98.2% (at pH=7), respectively, under sunlight. Fomesafen was also degraded at high percentage of 96% by the CeYMgO photocatalyst after 180 min under sunlight, but the initial pH of the contaminated water was low (pH=2.5). In addition, the T+G+CeYMgO floater degraded fomesafen but its efficiency was lower (90%) in comparison with the CeYMgO powder. The photocatalytic floater made with graphene+CeYMgO-powder had a higher content of defects (oxygen vacancies) than the T+G floater (as demonstrated by Raman and X-ray photoelectron spectroscopy (XPS) analyses). Therefore, it produced a higher degradation percentage for MB and fomesafen. Scavenger experiments were performed and found that the main oxidizing agents produced during the photocatalytic process are superoxide anions ( • O 2 − ), followed by holes (h+) and finally hydroxyl radicals (•OH). Furthermore, the T+G+CeYMgO photocatalytic floater induced the highest conversion from organic carbon to mineral carbon (77.98%), indicating that this floater produced the highest degradation of by-products. This investigation demonstrated that our photocatalytic floaters degraded contaminants due to the synergistic combination of porous CeYMgO, graphene with high absorption of sunlight and the entangled network of PET-based textile.