Photocatalytic Coatings for Environmental Applications^¶†

Abstract

A series of nano-and micronparticle-grade anatase and rutile titanium dioxide pigments have been prepared with various densities of surface treatments, particle size and surface area. Their photocatalytic activites have been determined in a series of paint films by FTIR, chalking, color, gloss change and weight loss after artifical weathering. The pigments have also been examined by rapid assessment methodologies using photodielectric microwave spectroscopy, 2-propanol oxidation and hydroxyl analysis. The microwave response under light and dark cycles provides an extended timescale probe of chargecarrier dynamics in the pigments. Pigment particle size, surface area and properties clearly play an important role in dispersion and any polymer-pigment interactions. Photooxidation studies on several types of paint films show a clear demarcation between nanoparticle-and pigmentary-grade titanium dioxide, with the former being more active because of their greater degree of catalytic surface activity. The photosensitivity of titanium dioxide is considered to arise from localized sites on the crystal surface (i.e. acidic OH), and occupation of these sites by surface treatments inhibits photoreduction of the pigment by ultraviolet radiation; hence, the destructive oxidation of the binder is inhibited. Coatings containing 2-5 % by weight alumina or alumina and silica are satisfactory for generalpurpose paints. If greater resistance to weathering is desired, the pigments are coated more heavily to about 7-10% weight. The coating can consist of a combination of several materials, e.g. alumina, silica, zirconia, aluminum phosphates of other metals. For example, the presence of hydrous alumina particles lowers van der Waals forces between pigments particles by several orders of magnitude, decreasing particle-particle l/Posted on the website on

Photocatalytic Behavior of Water-Based Styrene-Acrylic Coatings Containing TiO2 Sensitized with Metal-Phthalocyanine Tetracarboxylic Acids

“…Further diminishing the photocatalysts loading at 2.5 wt % reduces the rate of MB degradation. The experimental data showed similar results in the case of the other photocatalytic coatings and sustain other results already reported [44].…”

Photocatalytic Reaction of Gas-Phase Naphthalene on Paint- and Sunscreen-Coated Surfaces

“…The photocatalytic degradation of small organic molecules, such as formaldehyde, methanol, and 2-propanol, on paint-coated surfaces or thin films containing embedded TiO 2 nanoparticles has been studied [5][6][7][8][9][10]. To date, few studies have examined the destruction of large, semivolatile organic compounds (SVOCs) on paint films.…”

Methane and nitrous oxide emission from livestock manure

“…Another interesting mitigation technology for animal housing is use of titanium dioxide (TiO 2 ) paint on the interior walls. Industrial uses of TiO 2 stimulated its photocatalytic properties by UV light and lead to oxidation of NH 3 and N 2 O (Allen et al, 2005).…”