Photocatalytic decomposition of benzo-[a]-pyrene on the surface of acrylic, latex and mineral paints. Influence of paint composition

Degradation of polycyclic aromatic hydrocarbons (PAHs) in smoked sausages by ultraviolet irradiation

BACKGROUND

Ultraviolet (UV) irradiation has been widely employed to disinfect food, however, the efficacy of UV irradiation in degrading polycyclic aromatic hydrocarbons (PAHs) in smoked sausages has not been explored. In this article, the UV degradation ability of PAHs in smoked sausages was investigated with different UV irradiation conditions, including different irradiation powers, durations and wavelengths. The effects of UV radiation on the quality of sausages were also evaluated, and potential degradation mechanisms were elucidated.

RESULTS

The results showed that the irradiation duration was the primary determinant of PAHs degradation, achieving 84.4% and 84.2% degradation rates at 16 W and 32 W power for 30 min, respectively. Among the three UV wavelengths assessed, 254 nm demonstrated a significantly higher degradation rate for benzo[a]pyrene (BaP), PAH4 and PAHs compared to 365 nm and 310 nm. To further explore the degradation mechanism, UV irradiation was combined with water, 0.1 mol/L hydrogen peroxide (H2 O2 ) and 0.1 mol/L ascorbic acid (vitamin C) coatings. The 0.1 mol/L H2 O2 coating exhibited the most pronounced degradation effect, suggesting that the highly reactive oxygen hydroxyl radicals (·OH) generated by UV irradiation played a critical role in initiating redox reactions.

CONCLUSION

This systematic investigation paves the way for developing novel strategies to eliminate PAHs or other organic contaminants from smoked sausages. © 2023 Society of Chemical Industry.

Photocatalytic Decomposition of Acetaldehyde on Different TiO2-Based Materials: A Review

Purification of air from the organic contaminants by the photocatalytic process has been confirmed to be very perspective. Although many various photocatalysts have been prepared and studied so far, TiO2 is still the most commonly used, because of its advantageous properties such as non-toxicity, relatively low cost and high stability. Surface modifications of TiO2 were extensively proceeded in order to increase photocatalytic activity of the photocatalyst under both UV and visible light activations. The intention of this review paper was to summarize the scientific achievements devoted to developing of TiO2-based materials considered as photocatalysts for the photocatalytic degradation of acetaldehyde in air. Influence of the preparation and modification methods on the parameters of the resultant photocatalyst is reviewed and discussed in this work. Affinity of the photocatalyst surfaces towards adsorption of acetaldehyde will be described by taking into account its physicochemical parameters. Impact of the contact time of a pollutant with the photocatalyst surface is analyzed and discussed with respect to both the degradation rate and mineralization degree of the contaminant. Influence of the photocatalyst properties on the mechanism and yield of the photocatalytic reactions is discussed. New data related to the acetaldehyde decomposition on commercial TiO2 were added, which indicated the different mechanisms occurring on the anatase and rutile structures. Finally, possible applications of the materials revealing photocatalytic activity are presented with a special attention paid to the photocatalytic purification of air from Volatile Organic Compounds (VOCs).

Efficiencies Evaluation of Photocatalytic Paints Under Indoor and Outdoor Air Conditions

The removal of indoor and outdoor air pollutants is crucial to prevent environmental and health issues. Photocatalytic building materials are an energy-sustainable technology that can completely oxidize pollutants, improving in situ the air quality of contaminated sites. In this work, different photoactive TiO₂ catalysts (anatase or modified anatase) and amounts were used to formulate photocatalytic paints in replacement of the normally used TiO₂ (rutile) pigment. These paints were tested in two different experimental systems simulating indoor and outdoor environments. In one, indoor illumination conditions were used in the photoreactor for the oxidation of acetaldehyde achieving conversions between 37 and 55%. The other sets of experiments were performed under simulated outdoor radiation for the degradation of nitric oxide, resulting in conversions between 13 and 35%. This wide range of conversions made it difficult to directly compare the paints. Thus, absorption, photonic, and quantum efficiencies were calculated to account for the paints photocatalytic performance. It was found that the formulations containing carbon-doped TiO₂ presented the best efficiencies. The paint with the maximum amount of this photocatalyst showed the highest absorption and photonic efficiencies. On the other hand, the paint with the lowest amount of carbon-doped TiO₂ presented the highest value of quantum efficiency, thus becoming the optimal formulation in terms of energy use.

Nature-inspired CaCO3 loading TiO2 composites for efficient and durable photocatalytic mineralization of gaseous toluene

The accumulation of intermediates or final products on TiO₂ during photocatalytic volatile organic compounds (VOCs) degradation is typically neglected, despite the fact that it could result in the block of active sites and the deactivation of photocatalysts. Inspired from the natural formation of stalactite (CaCO₃ + H₂O + CO₂ ↔ Ca(HCO₃)₂), we fabricated CaCO₃ loading TiO₂ composites (CCT21) to realize the spontaneously transfer of accumulated final products (CO₂ and H₂O). Efficient and durable performance for gaseous toluene removal has been demonstrated and the cost of photocatalyst is greatly reduced by the comparison of specific activity. The introduction of CaCO₃ induces the interaction between TiO₂ and CaCO₃ to stimulate abundant activated electrons for the improvement on the adsorption and activation of reactants and the transformation of photogenerated carriers, and most importantly, facilitates the transfer of final products to release active sites and thus suppress the deactivation of TiO₂. Furthermore, we develop a facile method to immobilize CCT21 powder on flexible support, which greatly reduces the loss of photocatalysts and correspondingly enables the practical application of TiO₂-based products. Therefore, this work presents a novel nature-inspired strategy to address the challenge of deactivation, and advances the development of photocatalytic technology for environmental remediation.

The impact of photocatalytic paint porosity on indoor NOx and HONO levels

Photocatalytic materials are a potentially effective remediation technology for indoor air purification.

Photocatalytic degradation of H2S in the gas-phase using a continuous flow reactor coated with TiO2-based acrylic paint

For the photocatalytic degradation of the hydrogen sulphide (H₂S) in the gas-phase it was developed a rectangular reactor, coated with acrylic paint supported on fiber cement material. The surface formed by the paint coverage was characterized structural and morphologically by scanning electron microscopy with energy dispersive X-ray and X-ray diffraction analysis. The flow rate and the inlet concentration of H₂S were evaluated as operational performance parameters of the reactor. Removal efficiencies of up to 94% were obtained at a flow rate of 2 L min^-1 (residence time of 115 s) and inlet concentration of 31 ppm of H₂S. In addition, the H₂S degradation kinetics was modelled according to the Langmuir-Hinshelwood (L-H) model for the inlet concentrations of 8-23 ppm of H₂S. The results suggest that flow rate has a more important influence on photocatalytic degradation than the inlet concentration. It is assumed that H₂S has been oxidized to SO42- , a condition that led to a deactivation of the photocatalyst after 193 min of semi-continuous use.

Impact of paint matrix composition and thickness of paint layer on the activity of photocatalytic paints

Silicate, acrylic and latex photocatalytic paints were analyzed in regards to impact of paint matrix composition and paint layer’s thickness on performance in two photocatalytic tests. These included performances in photocatalytic decomposition of benzo[a]pyrene (BaP) and assessment of photocatalytic activity through use of smart ink test. Silicate photocatalytic paints displayed lower photocatalytic activity in comparison to acrylic and latex photocatalytic paints in both tests, despite the similar content of nanocrystalline TiO2. Measurements of depth of UV light penetration through the paints layer were performed and it appeared, that more porous structure of coating resulted in deeper penetration of UV light. In the case of acrylic paint, the thickness of the photocatalytic layer was around 9 μm, but for silicate paint DR this thickness was higher, around 21 μm.

Biodegradation of the benzo[a]pyrene-contaminated sediment of the Jiaozhou Bay wetland using Pseudomonas sp. immobilization

To remove benzo[a]pyrene (BaP) that has accumulated in the Jiaozhou Bay wetland sediment, two strains (JB1 and JB2) were selected from the BaP-contaminated the wetland sediment and immobilized in coal cinder and chitosan beads using entrapping and surface adsorption methods. Biodegradation of BaP in sediment was carried out in pots. The results showed that, supported by the coal cinder and chitosan beads, 71.9, 65.5, 58.9 and 66.1% of the BaP in the immobilized cells was degraded after 40d. These percentages were clearly higher than the 47.7% that degraded from free cells. Kinetic analysis indicated that the immobilized gel-beads might remove BaP by multiple control steps. Compared to the chitosan, coal cinder-entrapping beads exhibited a higher removal rate for BaP; however, the degradation rates from coal cinder- and chitosan-surface adsorption beads were almost the same. This result indicates that in addition to the BaP-degrading bacteria, carrier materials and immobilizing methods play an important role in determining the success of a biodegradation strategy.