Photo-reduction of heavy metal ions and photo-disinfection of pathogenic bacteria under simulated solar light using photosensitized TiO₂ nanofibers

Abstract

We report the photosensitization of electrospun titania nanofibers, with a mean diameter of 195 nm, by low bandgap silver sulfide nanoparticles of 11-23 nm mean size with the aim of treating heavy metal ions and pathogenic bacteria simultaneously under simulated solar light irradiation. The 17 nm Ag 2 S/TiO 2 nanofibers showed 90% photocatalytic reduction of Cr(VI) at pH of 3 with a pseudo-first order rate constant of 0.016 min À1 which is significantly better than the previously reported for Ag-Ag 2 S/TiO 2 composite particles. The antibacterial capability of the Ag 2 S/TiO 2 nanofibers was evaluated via photo-disinfection of the Gram-positive and Gram-negative bacterial strains. The smallest sized 11 nm Ag 2 S/TiO 2 nanofiber showed the best bactericidal efficiency of 100% and 90.6% against Gram-negative E. coli and Grampositive S. aureus after 1 h of irradiation, respectively, whereas, only 50% E. coli and 41% S. aureus were found to be inactivated in dark. Furthermore, a UV-O 3 treatment of the 11 nm Ag 2 S/TiO 2 nanofibers remarkably enhanced the antibacterial activity where 89% E. coli and 81% S. aureus were inactivated in just 10 min of the irradiation. Enhanced photocatalytic activity is attributed to the efficient charge separation and transfer and reduced electron-hole recombination induced by the effective heterojunction formation between TiO 2 and the optimally sized Ag 2 S nanoparticles. The disinfection nature of the Ag 2 S nanoparticles, role of the generated hydroxyl species under irradiation, and the cell wall damage mechanism is also discussed. This study demonstrates the potential use of these multifunctional composite TiO 2 nanofibers for water remediation.

The Roles of Nanomaterials in Conventional and Emerging Technologies for Heavy Metal Removal: A State-of-the-Art Review

“…This allows for more electrons to escape from pair recombination and become available for the reduction of Cr (VI) ions [152]. Photocatalysis have also shown the potential to photoreduce Cr (VI) into Cr (III) while exhibiting potential to kill harmful bacteria, such as E. coli (89%) and S. aureus (81%) within 10 min of irradiation on photosensitized TiO 2 nanofibers [160]. In recent years, the development of binary (bi-material) and ternary (tri-material) photocatalyst has intensified in search of combinations to produce photocatalyst that is responsive towards visible light, low recombination rates, and increased surface reactive sites.…”

The green, ultrafine cellulose-based porous nanofibrous membranes for efficient heavy metal ion removal through incorporation of chitosan by various electrospinning ways

“…This also severely restricts human normal production, life and further sustainable development. Several methods like ion-exchange, precipitation and oxidation, photocatalysis, separation and adsorption have been attempted to eliminate heavy metal ions in polluted water environment (Liu et al 2015;Ghafoor et al 2018). The adsorption is considered as the outstanding technology due to its low cost of investment and operation, facile process, high e ciency and reversibility for the decontamination (Olivera et al 2016).…”

Ex Situ Method for Photoreduction of the Cadmium Ion from Terbium-Loaded Bismuth Vanadium Oxide

“…Heavy metals such as lead, mercury, cadmium, nickel, and chromium are found in the wastewater of various industries such as mining, petrochemicals, pharmaceuticals, plastic products, paper, and fabric dyeing. − Because of the adverse effects of heavy metals, many of their derivatives are classified as pollutants . Penetration of heavy metals inside the body leads to various adverse effects and also many diseases . Inclusion of heavy metals’ in the marine bodies contributed to pollution and side effects in marine organisms …”

“…2 Penetration of heavy metals inside the body leads to various adverse effects and also many diseases. 5 Inclusion of heavy metals' in the marine bodies contributed to pollution and side effects in marine organisms. 6 Cadmium is toxic for human and animal health, which enters water through agriculture processes and chemical industries such as electroplating, metallurgical alloying, metal finishing, ceramics, cadmium-containing pigments, textile printing, plastic processing, cadmium-containing phosphate fertilizers, refined petroleum oil, and detergents.…”