Hematite (Fe ₂ O ₃ )-modified biopolymer for Rhodamine B degradation under visible light

This study deals with the preparation of a novel biomaterial by incorporating the hematite α-Fe₂O₃ onto crushed leaves of the Washingtonia filifera palm tree in their raw state and in extracted cellulose from the same plant. The incorporation of α-Fe₂O₃ was accomplished by hydrothermal route at 200 °C. The palm leaves, extracted cellulose, and synthesized products were characterized by thermal analysis (TG) and FT-IR spectroscopy. The latter revealed peaks at 524 and 449 cm⁻¹ for the synthesized material, attributed to vibrational deformation of the inorganic Fe-O bond. In contrast to the TG profile of raw palm leaves, the thermogram of the composite degrades in a single step at 343 °C. This one-step decomposition clearly indicates the chemical modification of our cellulose matrix and confirms the successful incorporation of the hematite α-Fe₂O₃ into the lignocellulose. The second part is devoted to α-Fe₂O₃ working as sensitizer in photocatalysis, it was characterized optically (<i>E_g</i>= 1.94 eV) and electrochemically with a flat band potential of −0.53 V_SCE. The conduction band (−0.73 V<i>_SCE</i>) is more cathodic than the potential of the O₂/O₂^•− couple (−0.52 V<i>_SCE</i>) and should reduce dissolved oxygen into reactive O₂^•− radical. The as-prepared materials were successfully tested in the photocatalytic degradation of Rh B (10 ppm) and the result gave an abatement of 60% on α-Fe₂O₃/lignocellulose under visible light irradiation (LED lamp) with a flux of 23 mW cm⁻². The kinetic obeys a first-order model with a half photocatalytic-life of ∼ 7 h.