Aging of photocatalytic coatings under a water flow: Long run performance and TiO 2 nanoparticles release

Josune Olabarrieta, Saioa Zorita, Iratxe Peña, Nerea Rioja, Oihane Monzón, Pablo Benguria, Lorette Scifo*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

53 Citations (Scopus)

Abstract

Although photocatalytic coatings may experience severe wearing in most of their application, little work has been done to investigate their aging in a comprehensive way. In this article, we present an original experimental protocol to simulate an accelerated aging of photocatalytic coatings under a water flow, and test it on two materials: a well-known commercial product, Pilkington Activ™, and an experimental coating. The influence of intrinsic properties of the coatings (chemical nature, thickness) as well as environmental parameters (water matrix, UV-light) is investigated while the consequences of aging are evaluated under three different endpoints, related either to the long run performance of photocatalytic coatings or their environmental impact: (i) loss of the photocatalytic activity, (ii) degradation of mechanical properties, and (iii) release of TiO 2 nanoparticles. It is observed that both photocatalytic coatings experienced a deactivation of their active sites upon prolonged immersion. The extent of deactivation varies depending on the coating, being around 20% for experimental coatings and 65% for Pilkington Activ™ but shows little dependency on water matrix or illumination. An alteration of mechanical properties is seen on experimental coatings, which was accompanied by TiO 2 emissions as high as 150.5μgL -1. Although no reduction in film hardness or adhesion could be evidenced for Pilkington Activ™, TiO 2 concentrations up to 30.8μgL -1 was detected in the aging water showing that some release of TiO 2 nanoparticles also took place on this material. Interestingly, a common mechanism of release, triggered by an interaction between TiO 2, NaCl and UVA could be identified. Most severe damages were observed in presence of sodium chloride. These results suggest that the use of photocatalytic coatings with surface-bound nanoparticles in environmental applications may entail new entries of nanomaterials into the aqueous medium. They also prove that aging assays are an effective way of assessing the emissions.

Original languageEnglish
Pages (from-to)182-192
Number of pages11
JournalApplied Catalysis B: Environmental
Volume123-124
DOIs
Publication statusPublished - 23 Jul 2012

Funding

This work was jointly funded by Cantabria Government in the framework of the AquaNAN project and TECNALIA Foundation under its internal Nanotechnology Programme. Great thanks are due to Txomin Laburu for his determining help in the design and elaboration of the aging flumes and Carmen del Río for ICP-OES measurements.

FundersFunder number
TECNALIA Foundation

    Keywords

    • Aging
    • Emissions
    • Photocatalytic coatings
    • TiO nanoparticles
    • Water flow

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