Photo-induced recovery, optical detection, and separation of noxious SeO<inf>3</inf>^2- using a mesoporous nanotube hybrid membrane

A macroscopic-scale disc-like membrane capable of photo-induced recovery, optical detection, and separation of ultra-trace levels of SeO<inf>3</inf>^2- was fabricated using a mesoporous TiO<inf>2</inf>-SiO<inf>2</inf> nanotube (TSN)-porous anodic alumina (PAA) hybrid. The synergistic pressure-assisted filling and condensed formation of TSN inside the entire PAA (200 nm channel neck size and 60 μm longitudinal length) were evident. This approach enabled fabrication of an optical, photo-induced macroscopic membrane sensor (MS) by direct embedding of an organic colorant onto the long and mesoporous TSN/PAA channels. The TSN-MS structure of uniformly aligned, long, interconnected, tubular and nano-sized channel-like pores integrated the control patterns of photo-induced SeO<inf>3</inf>^2- recovery/extraction through surface chelation. As a result, a stable and recyclable TSN-MS against long-term exposure to UV light (for several days) is produced. MS functionality in terms of optical detection and selective separation (i.e., rejection and permeation) of toxic SeO<inf>3</inf>^2- among a group of interferent ions was assessed using a simple desktop filtration technique. The developed TSN-MS holds promise for use in advanced indoor and outdoor recovery, detection, and separation of SeO<inf>3</inf>^2- from aquatic sources in a one-step process. Our findings expand efforts for the environmental approach for production of SeO<inf>3</inf>^2--free water, photo-hazardous SeO<inf>3</inf>^2- collection and management, and volume reduction of solution or solid wastes after multi-cyclic remediation.