Titanium dioxide (TiO₂) nanoparticles (NPs) are widely used in various industries and are increasingly found in environmental systems, especially in soil. However, the environmental behavior of TiO₂ NPs is still poorly understood. Hence, this study aims to fill this gap by investigating the short- and long-term effects of soil solutions on anatase and rutile NPs. The experiments were carried out using two soil types, which have very different chemical properties, in order to obtain a more nuanced picture of how these factors affect the stability, surface chemistry, and photocatalytic activity of TiO₂ NPs. The results indicate that acidic soil solutions with lower ionic strength tend to enhance the stability of TiO₂ NPs by preventing aggregation, while alkaline solutions with higher ionic strength promote aggregation and reduce photocatalytic activity by blocking active sites. Additionally, the adsorption of organic matter and other soil components on the nanoparticle surface further complicates their behavior, potentially reducing their photocatalytic efficiency. The interaction time plays a crucial role in determining the long-term fate of TiO₂ NPs in soil environments. Extended exposure to soil solutions leads to changes in crystallite size, surface charge, and the adsorption of functional groups, which, in turn, affect the NPs’ photocatalytic properties.

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.

The photocatalytic activity of semiconductors can be tuned by changing their morphological or structural properties. However, a simpler and direct method is the introduction of a cocatalyst, for example V₂O₅ or V₂O₅/V₄O₉. In the present work, this was the cocatalyst added to SrTiO₃. The deposition method was directed in such a way that the cocatalyst did not cover the surface of the SrTiO₃ completely. This way, the photocatalytic process (phenol conversion) takes place at the surface of the main catalyst, while the lifetime of the generated charge carriers is increased through electron trapping via the presence of vanadium oxides. The V₂O₅/V₄O₉ cocatalyst influences the recombination processes of excited electrons in SrTiO₃ by modifying the near-surface defects of SrTiO₃, and it can efficiently capture electrons due to the formed heterojunction. The V₄O₉ content enables efficient electron transfer, as its structure can accommodate V⁴⁺ in addition to V⁵⁺. Therefore, a mixed-phase semiconductor is more suitable as a cocatalyst than a single-phase semiconductor. In this work, the photocatalytic activity of SrTiO₃ was investigated in the presence of V₂O₅ (0–20 wt.%). It was found that all the samples that contained the cocatalyst showed higher photocatalytic activity than the unmodified SrTiO₃. The sample containing 10 wt.% of cocatalyst performed ~5.4 times better than pristine SrTiO₃ (35.87 µmol_phenol/g_catalyst, vs. 7.74 µmol_phenol/g_catalyst). This sample also contains a relatively high amount of V₄O₉ compared to the other samples, in addition to V₂O₅, which may be the main reason for the enhanced photocatalytic performance.

Inland water management is increasingly important under climate change due to the need for landscape-scale water retention, but in situ studies are limited by fluctuating, shallow, and intermittent water cover. This study simulated prolonged waterlogging under controlled laboratory conditions. Four agricultural soils (Calcisol, Arenosol, Chernozem, and Solonetz) were flooded for 40 days using identical 1:5 soil-to-water ratios at two temperature regimes, at 4 and 22 °C. Given that periodic water cover may conflict with agricultural production, particular attention was paid to crop-relevant indicators, including pH, water-soluble salts, and N, P, K. The laboratory simulation revealed significant differences among soil types and between temperature treatments. Elevated Mg concentrations limited the irrigation suitability of leachate derived from Calcisol, with Mg% values ranging from 57 to 64%, exceeding the 50% guideline threshold. Soil buffering capacity controlled phosphorus and potassium dynamics, resulting in stable or slightly increasing AL-soluble nutrient levels, except in low-buffering sandy soils where up to 3–4-fold variability was observed. Reductive conditions developed early in the Calcisol samples, supported by dissolved oxygen saturation values below 20% during the first days of the experiment. Oxygen saturation increased later, only exceeding 60% twice in the cooled Calcisol treatment, while nitrate–ammonium dynamics reflected changing redox conditions. Temperature significantly affected solubility and nutrient mobility, partly through its influence on microbial activity. These findings improve our understanding of inland water–soil interactions and support the development of sustainable, water-retentive land management strategies.

Silver (0–5 wt%) was reduced on the surface of barium titanates (BaTiO₃) to investigate its effect on the properties and photocatalytic activity of the support. Samples were characterized by X-ray diffractometry, diffuse reflectance spectroscopy, photoluminescence, transmission electron microscopy, photocurrent density, and linear sweep voltammetry. Their photocatalytic activity was evaluated by phenol degradation under UV light irradiation. A commercial BaTiO₃ without silver was used as a reference. Nominal silver amounts were consistent with the measured ones in the samples containing 0–3 wt% silver; however, at high nominal amounts (4–5 wt%), the measured silver content decreased significantly (~1.3 wt%). Samples containing larger silver particles had higher photoactivity than samples containing smaller silver particles. The sample containing 5 wt% silver performed the best, reaching a phenol degradation rate of 2.10 × 10⁻⁴ s⁻¹, over an order of magnitude higher than that of the non-silver-containing reference sample (1.47 × 10⁻⁵ s⁻¹). The enhanced photoactivity was associated with the larger silver particles covering less of the BaTiO₃ surface, leaving more active sites available, and with the silver hindering charge recombination by trapping the electrons and thus increasing the efficiency of holes.