PHOTO-FENTON REACTION OF DYES WITH Fe(III)-TREATED HYDROXYAPATITES AS HETEROGENEOUS CATALYSTS IN WATER

抄録

Fe(III)-treated hydroxyapatites, HAP-300-Fe and HAP-400-Fe, were prepared from hydroxyapatites, HAP-300 (stoichiometric type) and HAP-400 (Ca-deficient type), respectively, and applied to photo-Fenton reaction of dyes as heterogeneous catalysts in comparison with other Fe catalysts such as Fe₂O₃, FePO₄·2H₂O, and FeOOH. Among the Fe catalysts, HAP-400-Fe revealed the highest consumption and mineralization in photo-Fenton reaction of alizarin red S (ARS), and also indicated good catalytic activity to other dyes, alizarin, neutral red, methyl red, methyl orange (MO), Congo red, and indigo carmine. Generation of hydroxyl radical •OH as an oxidation species from H₂O₂ was observed in the all Fe catalysts by an indirect method using N, N-dimethylamino-4-nitrosoaniline, which is exclusively sensitive to •OH. In order to elucidate catalysis mechanism of Fe catalysts, kinetic investigation based on Michaelis-Menten theory was conducted in the reaction of ARS and MO. As a result, HAP-400-Fe indicated high ability of bearing many dye molecules but low degradative catalysis ability to H₂O₂, compared with Fe₂O₃. However, judging from high mineralization ability as well as repeating availability (5 times), HAP-400-Fe is considered as an excellent heterogeneous catalyst for photo-Fenton reaction.