The Influence of Surface Alumina and Silica on the Photocatalytic Degradation of Organic Pollutants

Abstract

Practical photocatalysis for degradation of organic pollutants must take into account the influence of other chemicals. Significant Al deposition on titania can occur at naturally occurring concentrations of dissolved Al. This paper reviews the author's work on the influence of deliberately deposited hydrous oxides of aluminium on the behavior of a ~130 m 2 g −1 rutile TiO 2 , and then compares the behavior of deposited alumina with that of deposited silica. On rutile some adsorbed nitrogen is infrared-active. Alumina and silica deposited on the rutile reduce, and ultimately eliminate, this infrared-active species. They also reduce photocatalytic oxidation of both propan-2-ol and dichloroacetate ion and the photocatalytic reduction of diphenyl picryl hydrazine. The surface oxides suppress charge transfer and may also reduce reactant adsorption. Quantitative measurement of TiO 2 photogreying shows that the adsorbed inorganics also reduce photogreying, attributed to the capture of photogenerated conduction band electrons by Ti 4+ to form Ti 3+ . The influence of adsorbed phosphate on photocatalysis is briefly considered, since phosphate reduces photocatalytic disinfection. In the context of classical colloid studies, it is concluded that inorganic species in water can significantly reduce photoactivity from the levels that measured in pure water.

Influence of Inorganic Ions and Organic Substances on the Degradation of Pharmaceutical Compound in Water Matrix

“…The most significant decrease for IBU concentration equal to 94% was obtained during the process conducted Additionally, it was determined that the presence of Al 3+ and Fe 3+ ions also decreases the efficiency of photochemical degradation of all investigated pharmaceutical compounds. In research [40] it was confirmed that Al 3+ ions can precipitate on the surface of a photocatalyst and block its photoactivity. Fe 3+ ions can also attract electrons emerging in the process of photoactivation of photocatalyst particles according to Equation (11) it equalled only to 27%.…”

“…Additionally, it was determined that the presence of Al and Fe ions also decreases the efficiency of photochemical degradation of all investigated pharmaceutical compounds. In research [40] it was confirmed that Al ions can precipitate on the surface of a photocatalyst and block its photoactivity. Fe ions can also attract electrons emerging in the process of photoactivation of photocatalyst particles according to Equation (11) In the case of the solution with AlCl the pharmaceuticals' removal rates obtained after 60 min of UV irradiation during photocatalysis reached correspondingly 91% for DCF, 66% for IBU and only 28% for CBZ.…”

Interactions of titania based nanoparticles with silica and green-tea: Photo-degradation and -luminescence

“…Utilization of organic materials for surface modification has typically involved bulk admixtures, which has been exploited successfully in the pigment industry [21,22] or the addition of antioxidants such as vitamin A, E, or C. Even though success has been achieved in both titania-based cosmetic applications and photocatalyst applications, a comparative study and understanding of the balance between these processes is yet to be fully realized.…”

Photocatalytic Removal of Microbiological Consortium and Organic Matter in Greywater

“…At this point, advanced treatment technologies have gained an interest due to their several advantageous properties. As one of the advanced oxidation technologies, the photocatalytic oxidation process provides an innovative and effective way of non-selective oxidation leading to complete mineralization under the specified conditions [8][9][10][11]. The mechanism of the photocatalytic oxidation process is based on the production of highly-reactive hydroxyl radicals under ultraviolet (UV, λ < 380 nm) irradiation in the presence of a semiconductor photocatalyst (e.g., TiO 2 ).…”