Immobilized TiO₂ on glass spheres applied to heterogeneous photocatalysis: photoactivity, leaching and regeneration process

Abstract

Heterogeneous photocatalysis using titanium dioxide as catalyst is an attractive advanced oxidation process due to its high chemical stability, good performance and low cost. When immobilized in a supporting material, additional benefits are achieved in the treatment. The purpose of this study was to develop a simple protocol for impregnation of TiO2-P25 on borosilicate glass spheres and evaluate its efficiency in the photocatalytic degradation using an oxidizable substrate (methylene blue), in a Compound Parabolic Concentrator (CPC) reactor. The assays were conducted at lab-scale using radiation, which simulated the solar spectrum. TiO2 leaching from the glass and the catalyst regeneration were both demonstrated. A very low leaching ratio (0.03%) was observed after 24 h of treatment, suggesting that deposition of TiO2 resulted in good adhesion and stability of the photocatalyst on the surface of borosilicate. This deposition was successfully achieved after calcination of the photocatalyst at 400 °C (TiO2-400 °C). The TiO2 film was immobilized on glass spheres and the powder was characterized by scanning electron microscopy (SEM), X-ray diffraction and BET. This characterization suggested that thermal treatment did not introduce substantial changes in the measured microstructural characteristics of the photocatalyst. The immobilized photocatalyst degraded more than 96% of the MB in up to 90 min of reaction. The photocatalytic activity decreased after four photocatalytic cycles, but it was recovered by the removal of contaminants adsorbed on the active sites after washing in water under UV-Vis irradiation. Based on these results, the TiO2-400 °C coated on glass spheres is potentially a very attractive option for removal of persistent contaminants present in the environment.

Packed Bed Photoreactor for the Removal of Water Pollutants Using Visible Light Emitting Diodes

“…In fact, the MB relative concentration gradually decreased in the run time and almost complete decolorization was achieved after 120 min of visible light irradiation. Several published papers have reported the removal of MB with fixed bed photoreactors irradiated by artificial light sources, as well as with solar photocatalytic reactors using structured photocatalysts (Table 1) [34][35][36][37][38]. For example, almost total MB decolorization was achieved after 48 h in the solar photoreactor proposed by Sutisna et al [34], in which TiO 2 nanoparticles were placed as coating on transparent granules and used in the prototype of a flat-panel photoreactor.…”

“…El-Mekkawi et al [35] observed the complete decolorization after 5 h under the sunlight irradiation using a solar concentrator photoreactor prototype with TiO 2 deposited on polyethylene terephthalate (PET) textile substrate sheets. In some cases, it was reported that MB degraded more than 96% in up to 90 min of reaction using TiO 2 immobilized on glass spheres [36]. However, the same authors used a lab scale compound parabolic collector reactor irradiated by lamp at high electrical power (300 W) simulating the solar spectrum.…”

Bi2O3@mSiO2 as an Environmentally Benign and Sustainable Solid Acid Catalyst for Benzoylation of Aromatics: Impact of Silica Encapsulation on Catalyst Leaching and Reaction Synergy

“…Similarly, some important processes such as waste water remediation, biofuel synthesis, and catalytic wet air oxidation reaction have also been marred by leaching of the active species. There are a few other commercially important reactions as well where leaching has been detected …”

Comparative Study of Four TiO2-Based Photocatalysts to Degrade 2,4-D in a Semi-Passive System

“…Amongst various fabrications and application methods, positioning a photocatalyst near the surface of water, and on a floating support have been investigated by several researchers as it allows higher oxygenation and illumination [17,[32][33][34][35][36]. Although the initial floating supported photocatalysts were shown to be effective to clean oil slicks on water [17], the ingestion risk by fishes and animals in water and uncertain toxicity of the degradation intermediates limited their development.…”