In this study, we compared the performances of three iron-containing crystalline and amorphous catalysts, that is, Fe-Zeo-A, Fe-ZSM-5, and Fe-silica, respectively, for the degradation of phenol in an aqueous solution. Catalytic activity for the degradation of phenol was assessed by heterogeneous photolysis, Fenton, and photo-Fenton oxidation. All catalysts exhibited higher activity in the photo-Fenton process. In addition, the catalyst stability was evaluated by the estimation of the iron loss and structural variations after the oxidation processes. Results revealed that Fe-silica and Fe-ZSM-5 exhibit higher catalytic activity (~100% phenol removal), while only 64% of phenol removal over Fe-Zeo-A was observed. Moreover, among all catalysts, Fe-ZSM-5 exhibited higher stability with low iron leaching, attributed to the uniform distribution of bonded Fe in the crystalline framework and narrow channels. On the contrary, amorphous Fe-silica exhibited higher iron leaching due to the presence of isolated iron species in the structure, leading to the partial involvement of a homogeneous reaction during the degradation of phenol. The structural stability of Fe-based catalysts was examined using microscopic and spectroscopic techniques.

Fe₂O₃/Mn₂O₃ nanocomposites and impregnated porous silicates (Fe₂O₃/Mn₂O₃@SiO₂ [FMS]) were prepared and investigated as catalytic adsorbents. The catalysts were applied for cationic and anionic dye pollutants in the adsorption, Fenton reaction, and photocatalysis processes at a pH of 7. Fe₂O₃/Mn₂O₃ nanoparticles (FM-NPs) were prepared using the co-precipitation method and were impregnated in SiO₂ by the sol–gel process. The synthesized materials were characterized using various sophisticated techniques. Results indicated that the impregnation of bi-metallic NPs in SiO₂ increased the surface area, and the function of the adsorbent also improved. FMS showed a significant adsorption effect, with 79.2% rhodamine B removal within 15 min. Fenton and photocatalyst reaction showed removal rates of 85.3% and 97.9%, respectively, indicating that negatively charged porous silicate attracts cationic pollutants. In the case of the anionic pollutant, Congo red, the adsorption reaction of FMS did not occur, and the removal rate of the photocatalyst reaction was 79%, indicating the repulsive force between the negatively charged silica and the anionic dye. Simultaneously, bi-metal-bonded FM-NPs facilitated the photocatalytic reaction, reducing the recombination of electron-hole pairs. This study provides new insights into the synthesis of FM-NPs and FMS as photocatalytic adsorbents and their photocatalytic mechanisms based on reaction conditions and contaminant characteristics. The developed materials have potential applications for environmental mitigation.

In this study, the effect of UV treatment on the physicochemical properties and structural variation of metal oxide-silica nanocomposites (Mn₂O₃-Fe₂O₃@SiO₂) has been investigated. Based on the results, UV irradiation significantly affects the nanocomposite structure, where SiO₂ network reconfiguration, change in surface OH group density, and surface area were observed. Erythromycin (ERY) has been chosen as a module pollutant to compare the performance of the pristine and UV-treated nanocomposites. The pristine nanocomposite had a high adsorption efficiency (99.47%) and photocatalytic activity (99.57%) at neutral pH for ERY in the first cycle, and this efficiency decreased significantly for the multiple cycles. However, different results have been observed for the UV-treated nanocomposite, where it retained its performance for ten consecutive cycles. This enhanced performance is attributed to the structural modifications after UV exposure, where increased surface area, pore volume, and OH group density resulted in an increased number of the possible mechanisms responsible for the adsorption/oxidation of ERY. Moreover, oxidation of adsorbed molecules by UV light after each cycle can also be another reason for enhanced removal. For the first time, the fate of ERY is studied using regenerated nanocomposites after the last cycle. LC/MS/MS results showed that ERY degraded in 20 min, and the produced reaction by-products were adsorbed by nanocomposites. This study could be a foundation research for the practical approaches for the regeneration of nanomaterials and the successful removal of organic pollutants from aquatic environments.

A series of novel Mn_xFe_y@SiO₂ (x,y = 1–20%) nanocomposites were synthesized for the first time via the sol-gel/combustion method with different content of precursors (Mn and Fe acetate salts). The effect of precursor content and ratio on physicochemical properties were observed by various characterization methods. Moreover, Rhodamine B (RhB) was chosen as the target pollutant to test the performance of these nanocomposites under a photocatalytic Fenton-like reaction. The results showed that the nanocomposite morphology improved by increasing Fe and Mn content. In this study, interesting behavior was observed in BET results which were different from the fact that increasing metal content can decrease the surface area. This study revealed that one metal could be more critical in controlling the properties than another. Moreover, the precursor ratio appears to have a more tangible effect on the surface area than the effect of precursor content. Among all synthesized nanocomposites, Mn₁Fe₅@SiO₂ showed the highest surface area of 654.95 m²/g. At optimum batch conditions (temp = 25 °C, catalyst dosage = 1 g L⁻¹, H₂O₂ = 75 mmolL⁻¹, and initial RhB concentration = 50 mg L⁻¹), complete removal (simultaneous adsorption/degradation) occurred using Mn₁Fe₅@SiO₂ at neutral pH. This study showed that the designed nanomaterial could be used as a dual functional adsorbent/photocatalyst in different environmental applications.

In the last decades, the removal of benzene, toluene, ethylbenzene, and xylene (BTEX) has been considered a major environmental crisis. In this study, two novel nanocomposite materials (Fe₂O₃/SiO₂ and Fe₂O₃-Mn₂O₃/SiO₂) that have regeneration ability by UV irradiation have been fabricated to remove BTEX at ambient temperature. This research revealed that both nanocomposites could remove more than 85% of the BTEX in the first cycle. The adsorption capacities followed the order of ethylbenzene > m-xylene > toluene > benzene as in the molecular weight order. The reusability test using UV irradiation showed that the performance of Fe₂O₃/SiO₂ decreased drastically after the fifth cycle for benzene. On the other hand, when Mn is located in the nanocomposite structure, Fe₂O₃-Mn₂O₃/SiO₂ could maintain its adsorption performance with more than 80% removal efficiency for all the BTEX for ten consecutive cycles. The difference in the reusability of the two nanocomposites is that the electron energy (from the valence band to the conduction band) for BTEX decomposition is changed due to the presence of manganese. This study provides a promising approach for designing an economical reusable nanomaterial, which can be used for VOC-contaminated indoor air.

Objectives : Recently, energy-related research has shifted from developing alternative energy to the efficient management technology of the produced energy. As an alternative, research on phase change materials (PCMs) capable of absorbing and releasing heat as an energy medium has been conducted. This study developed a more efficient heat storage medium using activated carbon as a medium for the phase change material. At the same time, we developed a method for efficiently impregnating the phase change material into the activated carbon pores.Methods : The activated carbon used in this experiment was charcoal powder activated carbon (250-350 mesh) and granular activated carbon. The inorganic phase change materials used in the experiment was manganese nitrate hexahydrate. The method for impregnating the phase change material was pressurization method and dilution method. The heat absorption / emission capacity of the developed material was examined within the range of 10℃ to 50℃.Results and Discussion : The Scanning electron microscope (SEM) and Transmission electron microscopy energy-dispersive X-ray spectroscopy (TEM-EDX) analysis showed that the phase change material was filled in the pore of activated carbon. When the phase change material is filled by the pressurized method, the material properties of manganese nitrate hexahydrate are reflected, resulting in absorption and release of heat at each phase change temperature. As a result of experiments for the selection of the optimum solvent in the phase change material filling study using the dilution method, when ethanol was used as the solvent, the heat absorption was clearly observed even after the phase change material was loaded. As a result of selecting the optimal dilution ratio, the ratio of ethanol was determined to be 1:1 as the dilution ratio with the lowest amount of floating activated carbon. The optimal solvent removal method experimental results show that the heat absorption/release section occurred when the ethanol was removed by evaporation at 85℃ temperature.Conclusions : 1) Both the pressurization method and the dilution method are filling methods in which inorganic phase change materials can be immobilized inside activated carbon, and heat absorption and release characteristics are maintained even after loading. 2) The heat absorption release was maintained for ethanol and the optimal dilution ratio was 1:1. 3) In case of the dilute solvent removal method, the heat absorption/release capacity was maintained when the solvent was removed using only the vaporization method.