Bovine bone-based activated carbon composite containing nanomagnetite as a catalyst for photo-Fenton reactions

Magnetic composites (MC) prepared from magnetite nanoparticles (MNP) and activated carbon from bovine bone (AC) in different proportions (75/25, 50/50, and 25/75) were used as catalysts in the photo-Fenton process to degrade methylene blue (MB) in aqueous solution. The materials were prepared by the citrate-nitrate sol-gel synthesis method and used as catalysts in the photo-Fenton process. The photocatalytic tests were performed in a cylindrical reactor with a 4.13-cm internal diameter and 300-mL maximum capacity, equipped with 9.9-W visible light lamps. The specific surface area of the MC increased by up to 1138.39% with the addition of AC. Morphological analysis confirmed the anchoring of MNPs on the AC surface. The band gap values of the materials ranged from 1.16 to 1.55 eV and increased proportionally with the addition of AC to the MC compositions. MC-75/25 and MC-50/50 presented predominantly superparamagnetic behavior, while for MC-25/75 superparamagnetic and superimposed paramagnetic phases were observed. All samples showed good reduction of the MB concentration, exceeding 80% after 10 cycles of use. The mineralization advanced extensively to simple organic acids, proving the non-generation of harmful by-products and the efficiency of this photocatalytic system. The use of magnetic composites favored the efficient separation of the catalyst without causing secondary pollution, in addition to increasing the stability and reusability of the catalysts.