Up to now, the use of TiO₂ has been considered a promising advanced technology for organic pollutants removal from air or water, since it has high biological and chemical stability, high photoactivity, low toxicity, and low-cost production. However, there are issues to be addressed in enhancing TiO₂ performance, and one of the current key issues is redesigning UV-active photocatalysts and making them active in the visible region of the electromagnetic spectrum. This way, solar light absorption will be insured, and thus, a more efficient photocatalyst could be obtained. For this reason, conjugated polymers and their derivatives are considered to act as photosensitizers, being able to shift the TiO₂ activity from the UV to the visible region. Therefore, this study focuses on the synthesis of TiO₂/conjugated polymer systems, which was accomplished by the deposition of poly-3,4-ethylene-dioxy-thiophene (PEDOT [-C₆H₄O₂S-]_n), a low-band semiconductor with an excellent stability due to its extending π-conjugated electron system, on titania nanoarchitecture. First of all, a TiO₂ nanoarchitecture was synthesized by an ultrasound-assisted sol–gel method. Then, TiO₂/PEDOT systems were obtained and characterized by using different techniques such as X-ray diffraction, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, UV–Vis diffuse reflectance, and N₂ sorption measurements. The synthesized composites confirmed their mesoporosity and lower band gap values compared to bare titania, which clearly shows the ability to work as photocatalysts under visible-light activity. Further, we demonstrated that an organic pollutant, Congo Red dye, used as a model molecule could be photodegraded with the synthesized TiO₂/PEDOT systems, with efficiencies of up to 95% in the case of T_convPEDOT under UV light and up to 99% for T_convPEDOT under visible-light irradiation, accomplishing in this way a successful synthesis of visible-light-activated titania photocatalyst.

Nano-sized magnesium ferrites were synthesized by the sol-gel auto-combustion method using a variety of chelating/combustion agents: tartaric acid, citric acid, cellulose, glycine, urea and hexamethylenetetramine. The original purpose of this work was the synthesis of nano-sized magnesium ferrite by using, for the first time, cellulose and hexamethylenetetramine as chelating/combustion agents. Synthesized samples were subjected to different heat treatments at 773 K, 973 K and, respectively 1173 K in air. The disappearance of the organic phase and nitrate phase with the spinel structure formation was monitored by infrared absorption spectroscopy. Spinel structure, crystallite size and cation distribution were evaluated by X-ray diffraction data. The morphology of as-prepared powders was studied using scanning electron microscopy. The magnetic and dielectric properties were studied for the obtained samples.

Spinel chromite nanoparticles are prospective candidates for a variety of applications from catalysis to depollution. In this work, we used a sol–gel auto-combustion method to synthesize spinel-type MgCr₂O₄ nanoparticles by using fructose (FS), tartaric acid (TA), and hexamethylenetetramine (HMTA) as chelating/fuel agents. The optimal temperature treatment for the formation of impurity-free MgCr₂O₄ nanostructures was found to range from 500 to 750 °C. Fourier transform infrared (FTIR) spectroscopy was used to determine the lattice vibrations of the corresponding chemical bonds from octahedral and tetrahedral positions, and the optical band gap was calculated from UV–VIS spectrophotometry. The stabilization of the spinel phase was proved by X-ray diffraction (XRD) and energy-dispersive X-ray (EDX) analysis. From field-emission scanning electron microscopy (FE-SEM), we found that the size of the constituent particles ranged from 10 to 40 nm. The catalytic activity of the as-prepared MgCr₂O₄ nanocrystals synthesized by using tartaric acid as a chelating/fuel agent was tested on the decomposition of hydrogen peroxide. In particular, we found that the nature of the chelating/fuel agent as well as the energy released during the auto-combustion played an important role on the structural, optical, and catalytic properties of MgCr₂O₄ nanoparticles obtained by this synthetic route.

The paper presents the synthesis and characterization of new cobalt ferrite-lignin hybrids. The hybrids were obtained through the combustion of cobalt nitrate and ferric nitrate, two kinds of lignin being used as combustion agents. The temperatures of calcination were 500 °C and 900 °C, respectively. The hybrids were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS). The magnetic properties were also assessed by vibrating sample magnetometer system (VSM). This facile synthesis method made it possible to obtain cobalt ferrite-lignin hybrids with a spinel structure. Their particle sizes and crystallite sizes have increased with an increment in the calcination temperature. A different occupancy of cations at octahedral and tetrahedral sites also occurred upon the increase in temperature. The hybrids comprising organic lignin presented the best magnetic properties.

This paper presents aspects related to water pollution with heavy metals from the Tarnita mining area before and after the cessation of the mining activity. The impact of heavy metals on waters is important because these metals have a negative impact on both human health and aquatic ecosystems. All research data showed that, even the mining activities from this area were suspended, the sterile still pollutes the soil and water

In this research, we reported on the formation of highly porous foam SrTiO₃/NiFe₂O₄ (_100−xSTO/_xNFO) heterostructure by joint solid-state and sol-gel auto-combustion techniques. The colloidal assembly process is discussed based on the weight ratio x (x = 0, 25, 50, 75, and 100 wt %) of NiFe₂O₄ in the _100−xSTO/_xNFO system. We proposed a mechanism describing the highly porous framework formation involving the self-assembly of SrTiO₃ due to the gelation process of the nickel ferrite. We used a series of spectrophotometric techniques, including powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), N₂ adsorption isotherms method, UV-visible diffuse reflectance spectra (UV-Vis DRS), vibrating sample magnetometer (VSM), and dielectric measurements, to investigate the structural, morphological, optical, magnetic, and dielectric properties of the synthesized samples. As revealed by FE-SEM analysis and textural characteristics, SrTiO₃-NiFe₂O₄ nanocomposite self-assembled into a porous foam with an internally well-defined porous structure. HRTEM characterization certifies the distinctive crystalline phases obtained and reveals that SrTiO₃ and NiFe₂O₄ nanoparticles were closely connected. The specific magnetization, coercivity, and permittivity values are higher in the ₇₅STO/₂₅NFO heterostructure and do not decrease proportionally to the amount of non-magnetic SrTiO₃ present in the composition of samples.