Shuji Fukahori

Capturing of bisphenol A photodecomposition intermediates by composite TiO2–zeolite sheets

Abstract Two types of powders, titanium dioxide (TiO 2 ) photocatalyst and zeolite adsorbent, were made into a paper-like composite by a papermaking technique using a dual polyelectrolyte system. The photodegradation behavior of bisphenol A (2,2-bis(4-hydroxyphenyl)propane, BPA) in water was investigated under UV irradiation. It was found that TiO 2 sheets could photocatalytically decompose BPA in an aqueous medium. Composite TiO 2 –zeolite sheets, however, demonstrated a higher efficiency for BPA removal from water than did zeolite-free TiO 2 sheets owing to the synergistic effect obtained through the combined use of TiO 2 and zeolite, as reported in our previous study. Furthermore, the total organic carbon (TOC) content of the system was reduced, evidently through the use of composite sheets, rather than a TiO 2 powder suspension or zeolite-free TiO 2 sheets. Trace amounts of intermediates resulting from BPA degradation were detected in the water treated with the composite sheets. In general, various intermediates are formed during the TiO 2 photodecomposition of organic compounds, which can potentially cause a secondary pollution because the degradation products sometimes turn out to be more hazardous than the parent compound. The composite TiO 2 –zeolite sheets prepared in the present study helped to overcome this problem by allowing the elimination of BPA without the release of hazardous intermediates into water: most of the intermediates were temporarily captured by the zeolite adsorbent contained in the composite sheets, and eventually decomposed through TiO 2 photocatalysis. Paper-like TiO 2 –zeolite composites clearly offer great advantages in efficacy and safety for the aqueous decomposition of BPA.

Selective oxidation of benzyl alcohol using RuHAp-containing sheet composites

Ru-containing hydroxyapatite (RuHAp) powder was successfully impregnated into sheet composites using a papermaking technique, and its catalytic efficiency was investigated. The RuHAp powder was homogeneously scattered over the fiber-mix networks that had been tailored within the catalyst sheet. RuHAp-containing sheets demonstrated superior performance to RuHAp beads for the selective oxidation of benzyl alcohol to benzaldehyde in a batch reaction process and the efficiency was equivalent to that of RuHAp powder. Catalytic performance was also evaluated in a continuous fixed-bed column reactor and RuHAp sheets showed higher oxidation efficiency than both RuHAp powder and beads. The porous structure of composites seemed to improve the effective transport of benzyl alcohol to RuHAp surfaces which were immobilized within the sheets, resulting in enhanced catalytic performance.