Solar photocatalytic degradation of methylene blue dye and 4-CP herbicide by using a biodegradable fiber support decorated with Ce_0.9Bi_0.1O₂ porous nanoparticles

Graphene microflakes were deposited on a biodegradable support of coconut/agave fibers to fabricate floatable photocatalytic (FG) composites. Later, Ce_0.9Bi_0.1O₂ (BiCeO) nanoparticles were synthesized by Pechini method and these nanoparticles with cubic phase were deposited on the FG composites. SEM images confirmed the presence of porous BiCeO nanoparticles on the surface of coconut/agave fibers. The photocatalytic performance of the FG, BiCeO powder and FG/BiCeO composites was evaluated by degrading methylene blue (MB) dye under natural solar irradiation. The MB (20 ppm) dissolved in tap water was degraded with efficiencies of 59 %, 92 % and 100 % by using the FG, BiCeO powder and FG/BiCeO composite, respectively. Moreover, the 4-CP herbicide was degraded with efficiencies of 86 % and 94 % by utilizing the BiCeO powder and the FG/BiCeO composite, respectively. In addition, scavenger experiments demonstrated that the main oxidizing agent generated for the degradation of MB and 4-CP are the superoxide anions (·O₂^-), followed by the holes (h⁺) and (·OH) radicals. Also, we found that the clean water obtained with the use of the FG/BiCeO composite had the lowest content of organic carbon (21.7 %), suggesting that most of the by-products (formed during the breakage of the MB molecule) were eliminated. Overall, the results of this research demonstrate that biodegradable photocatalytic composites can be fabricated from coconut/agave fibers at low cost. Those ones are not only floatable but can also be activated with solar light. Those last characteristics could be useful for the elimination of traces of dangerous organic contaminants in water treatment plants.