Treatment of Coliphage MS2 with Palladium-Modified Nitrogen-Doped Titanium Oxide Photocatalyst Illuminated by Visible Light

Abstract

A palladium-modified nitrogen-doped titanium oxide (TiON/-PdO) photocatalytic fiber was synthesized on a mesoporous activated carbon fiber template by a sol-gel process. Calcination of the coated fibers resulted in a macroporous interfiber structure and mesoporous photocatalyst coating. Atomic ratios of major photocatalyst constituents determined by X-ray photoelectron spectroscopy analyses were N/Ti approximately equal to 0.1 and Pd/-Ti approximately equal to 0.03. X-ray diffraction analyses revealed that the photocatalyst had an anatase structure and palladium additive was present as PdO. Triplicate batch experiments performed with MS2 phage (average initial concentration of 3 x 10(8) plaque forming units/mL) and TiON/PdO photocatalyst at a dose of 0.1 g/L under dark conditions revealed the occurrence of virus adsorption on the photocatalyst fibers at a rate that resulted in equilibrium within 1 h of contact time with corresponding virion removals of 95.4-96.7%. Subsequent illumination of the dark-equilibrated samples with visible light (wavelengths greater than 400 nm and average intensity of 40 mW/cm2) resulted in additional virus removal of 94.5-98.2% within 1 h of additional contact time. By combining adsorption and visible-light photocatalysis, TiON/PdO fibers reached final virus removal rates of 99.75-99.94%. Spin trapping electron paramagnetic resonance (EPR) measurements confirmed the production of *OH radicals by TiON/PdO under visible light illumination, which provided indirect evidence about MS2 phage being potentially inactivated.

Adsorption of MS2 on oxide nanoparticles affects chlorine disinfection and solar inactivation

“…E. coli cells in log phase of growth in tryptic soy broth solution were collected as the host cells. MS2 were grown in E. coli suspensions and purified by sequential centrifugation and filtration with minor modifications (Li et al, 2008b). Briefly, after cell lysis and virus release, debris was removed via microfiltration through 0. w a t e r r e s e a r c h 6 9 ( 2 0 1 5 ) 5 9 e6 7…”

Solar photocatalysis for water disinfection: materials and reactor design

“…This is the case for a commercial non-concentrating solar CPC Some authors have investigated the cost of solar water disinfection (SODIS), using small scale CPC reactors for household users in developing countries. Ubomba-Jaswa and coworkers 48 reported that a 25L-CPC batch reactor could provide 70 solar disinfected water at a total treatment cost of $0.2 per 100L, taking into account that the estimated photo-reactor built cost is $200 with 10 years of operational life. An advantage of the CPC system is the modular system, and Polo-López and co-workers 49 reported that a 6-tube automated sequential CPC batch reactor 75 could provide solar disinfected water with a total cost of $0.23 per 100L.…”

“…The concentric tube arrangement (a tube within a tube) with CPC was the most effective configuration. Photocatalysis has advantages in terms of the non-recovery of inactivated organisms and the inactivation of 70 SODIS resistant organisms. 57 Sordo and co-workers 60 studied the photocatalytic inactivation of E. coli with immobilized TiO 2 in two different configurations (a wall and a fixed-bed reactor) in a solar 10L-CPC pilot plant, comparing the use of a slurry reactor and the solar disinfection without catalyst.…”

“…Another example is palladium-modified 65 nitrogen-doped titanium oxide (TiON/PdO) supported on a mesoporous-activated carbon fiber templated by a sol-gel process. 70 A combination of adsorption and visible-light photocatalysis resulted in highly efficient virus deactivation. A further example, is the use of graphene-TiO 2 nanocomposites.…”

“…The mechanism (Figure 2) of photocatalytic disinfection 4, 5, 7-10 is as follows: The absorption of a photon from the solar energy 65 Titanium dioxide based photocatalysts (band gap of 3.2 eV) on which most of the research has focused until now, possesses a relatively high self-sterilisation under ultraviolet (UV) light (wavelength <390 nm). However, introduction of artificial UV light sources is not practical in remote areas where there is a lack 70 of power supplies. Utilisation of the main part of the solar spectrum by the development of photocatalysts (Figure 2) that can yield high photocatalytic activity under visible light 7,[11][12][13][14][15][16][17][18][19][20][21] would be highly beneficial in remote regions.…”