The elimination of organic molecules from wastewater is required to prevent harm to aquatic creatures. In the past, it has been demonstrated that zeolite-based systems provide excellent prospects for wastewater treatment; nonetheless, the majority of zeolite systems documented to date suffer from sinking in water and a saturated adsorption site. In the present work, we endeavored to create zeolite-based composite systems with excellent floatability, adsorption capacity, and photocatalytic activity. Furthermore, we verified that these composites could be easily removed from the treated water. Consequently, a tri-layer floating photocatalyst/adsorbent was created by deposition of silicalite-1, a pure silica MFI-type zeolite (PSZ), and TiO2 on hollow glass microspheres (HGMs). To create floating adsorbents, a thin coating of silicalite-1 was crystallized on the thick walls of HGMs (PSZHGMs). Using the sol-gel technique, a layer of TiO2 was placed on PSZ-HGM surfaces to create photocatalytic composites (TiO2/PSZ-HGMs). By introducing HGMs to an alkali solution comprising tetrapropylammonium hydroxide and tetraethyl orthosilicate, followed by hydrothermal synthesis at 180°C for 40 hours, excellent PSZ coverage, and attachment were obtained on HGM surfaces. TiO2 could cover the PSZ surface uniformly without blocking the zeolite pores during subsequent deposition. Using methylene blue, the wastewater treatment capacity of the synthesized materials was determined (MB). TiO2/PSZ-HGMs, which displayed both photocatalytic and adsorption capabilities, operated synergistically with UV-C irradiation to decrease MB content by 98% in 2 h. Consequently, these materials may have considerable promise in wastewater treatment operations.
Reference: Nijpanich S, Hagio T, Murase K, Park J H, Kamimoto Y, Sakdapipanich J, Terashima C, Chanlek N, Ichino R. A tri-layer floating photocatalyst/adsorbent for the removal of organic compounds from wastewater: Layer-by-layer deposition of silicalite-1 and titania on hollow glass microspheres. Environmental Technology & Innovation 2022: 26: 102242.