Effet of chemical compounds in soil solution to the photocatalytic activity of TiO₂ NPs.

Nanotechnology, especially in the field of photocatalysis, has witnessed rapid advancements, with titanium dioxide being one of the most widely used photocatalysts. As the use of products containing photoactive nanomaterials increases, concerns have arisen regarding their potential release into the environment over time. This release can impact soil, groundwater, and surrounding ecosystems, resulting in nanoparticles being dispersed in water and eventually depleted from the system. This study aimed to investigate how different soil solutions affect the structural, textural properties, and photocatalytic activity of titanium dioxide-based, commercial reference Evonik Aeroxide P25. The Regosol soil solution, characterized by acidic pH, low ionic content, and high organic matter content, induced nanoparticle aggregation and bandgap changes. In addition, the acidic pH hindered the adsorption process, potentially affecting the photocatalytic processes. In contrast, the Chernozem soil solution, with slightly alkaline pH, high ionic content, and low organic matter content, did not significantly alter the morphology or structure of the material. However, various organic compounds were absorbed on the surface, reducing the availability of active sites. The study highlights the importance of understanding the influence of soil solutions on nanomaterials, as it impacts their properties and environmental risks. Results show that the material is still activated, i.e., it can exert its photoactive effect on the environment. This sheds light on the challenges posed by nanoparticles in soil, particularly in terms of their toxicity and consequences for the surrounding ecosystems. The study underlines the need for further research in this area to assess potential risks and optimise the use of nanomaterials in environmental remediation.

Cesium lead halide nanostructures (CsPbX₃, where X = I or Br) are increasingly popular for solar cell applications, but their waste management remains underdeveloped, raising concerns about their potential accumulation in soil. This study investigates the environmental stability of CsPbI₃ and CsPbBr₃ nanostructures synthesized at different temperatures. Phenol was chosen as a model pollutant for the photocatalytic activity investigations, and the samples at 130 °C showed the ideal balance in terms of stability and activity. Therefore, these samples were then interacted with acidic and basic artificial soil extracts, thus representing the soil solution under different environmental conditions. X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray fluorescence (XRF), diffuse reflectance spectroscopy (DRS), and infrared (IR) spectroscopy were used to assess the material changes, while Pb leaching after interaction with soil extracts was measured by inductively coupled plasma mass spectrometry (ICP-MS). CsPbI₃ exposed to acidic extracts leached Pb, I, and Cs (as CsI), while PbI₂ stayed insoluble. Alkaline extracts caused minimal Pb leaching, indicating recrystallization, and CsPbBr₃ showed similar behavior. ICP-MS measurements showed that Pb concentrations were higher in acidic soil extracts than in basic ones. Pb concentrations increased with longer exposure. CsPbI₃ showed lower Pb concentrations than CsPbBr₃, suggesting that CsPbI₃ is more stable. These findings emphasize the stabilization strategies-such as chemical modifications, protective surface coatings, or composite material designs-to improve the durability of CsPbX₃ nanomaterials under realistic environmental conditions. Without such advancements, the large-scale deployment of these perovskites and nanostructures could pose significant environmental risks.

The present study aimed to investigate the interaction between strontium titanate photocatalysts and alkaline soil (solonetz) soil solutions. For this purpose, one commercially available and several synthesized strontium titanates were considered. The photocatalytic activity and material characteristics were assessed before and after immersion in the soil solutions. All samples were characterized by X-ray diffractometry (XRD), infrared spectroscopy (IR), diffuse reflectance spectroscopy (DRS), and scanning electron microscopy (SEM). After interaction with the soil solution, most of the samples became more active for phenol degradation. It was found that the crystalline structure of each sample was preserved, while the primary crystallite sizes decreased after both phenol degradation and immersion in solonetz soil solutions. Moreover, the surface of all synthesized nanostructures was covered by organic residues from either the soil solution or the by-products of phenol degradation. This was also visible from the DR spectra, as an intensive color change was observed. The bandgaps of most samples were also changed, except for the commercial material. The results imply that it is important to investigate the ecofriendly nature of any photocatalytic material, as it tends to influence the surrounding environment. This is important, as solar photocatalysis is rising among the possible methods for water purification and disinfection.

Nanotechnology, especially in the field of photocatalysis, has witnessed rapid advancements, with titanium dioxide being one of the most widely used photocatalysts. As the use of products containing photoactive nanomaterials increases, concerns have arisen regarding their potential release into the environment over time. This release can impact soil, groundwater, and surrounding ecosystems, resulting in nanoparticles being dispersed in water and eventually depleted from the system. Therefore, this study aimed to investigate how different soil solutions affect the structural, textural properties, and photocatalytic activity of titanium dioxide-based, commercial reference Evonik Aeroxide P25. The investigation found that Evonik Aeroxide P25 interacted differently with soil solutions based on their properties. The Regosol soil solution induced nanoparticles aggregation and band gap changes, attributed to its high organic matter content. Additionally, the acidic pH of Regosol hindered adsorption, potentially affecting photocatalytic processes. In contrast, the Chernozem soil solution did not significantly alter the morphology or structure of the material, but various organic compounds were adsorbed on the surface, potentially acting as electron traps and reducing active site availability. High concentrations of F–, Cl–, and NO3– ions in the Chernozem solution also hindered the photocatalytic activity of P25. The study highlights the importance of understanding the influence of soil solutions on nanomaterials, as it impacts their properties and environmental risks. Results show that the material is not fully inactivated, i.e. it can exert its photoactive effect on the surface. This sheds light on the challenges posed by nanoparticles in soil, particularly in terms of their toxicity and consequences for the surrounding ecosystems. The study underlines the need for further research in this area to assess potential risks and optimise the use of nanomaterials in environmental remediation.