Search Results (338)

The development of sustainable and functional nanocomposites has attracted considerable attention in recent years due to their broad spectrum of potential applications, including wood preservation. Also, a global goal is to reuse the large volumes of waste for environmental issues. In this context, the aim of the study was to obtain soda lignin particles, to graft ZnO nanoparticles onto their surface and to apply these hybrids, embedded into a biodegradable polymer matrix, as protection/preservation coating for oak wood. The organic–inorganic hybrids were characterized in terms of compositional, structural, thermal, and morphological properties that confirm the efficacy of soda lignin extraction and ZnO grafting by physical adsorption onto the decorating support and by weak interactions and coordination bonding between the components. The developed solution based on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and lignin-ZnO was applied to oak wood specimens by brushing, and the improvement in hydrophobicity (evaluated by water absorption that decreased by 48.8% more than wood, humidity tests where the treated sample had a humidity of 4.734% in comparison with 34.911% for control, and contact angle of 97.8° vs. 80.5° for untreated wood) and UV and fungal attack protection, while maintaining the color and aspect of specimens, was sustained. L.ZnO are well dispersed into the polymer matrix, ensuring a smooth and less porous wood surface. According to the results, the obtained wood coating using both a biodegradable polymeric matrix and a waste-based preservative can be applied for protection against weathering degradation factors, with limited water uptake and swelling of the wood, UV shielding, reduced wood discoloration and photo-degradation, effective protection against fungi, and esthetic quality. Full article

The natural sunlight driven photocatalytic degradation of organic pollutants is a sustainable solution for water purification. The use of heterojunction nanocomposites in this process shows promise for improved photodegradation efficiency. In this work, nanocrystalline Zn₂SnO₄/SnO₂ obtained by the solid-state synthesis method was tested as a heterojunction photocatalyst material for the degradation of methylene blue (MB) and Rhodamine B (RhB) dyes as single and multicomponent systems in natural sunlight. Characterization of the structure and morphology of the synthesized nanocomposite using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) combined with energy dispersive X-ray spectroscopy (EDS), and photoluminescence (PL) spectroscopy confirmed the formation of Zn₂SnO₄/SnO₂ and heterojunctions between Zn₂SnO₄ and the SnO₂ nanoparticles. A photodegradation efficiency of 99.1% was achieved in 120 min with 50 mg of the photocatalyst for the degradation of MB and 70.6% for the degradation of RhB under the same conditions. In the multicomponent system, the degradation efficiency of 97.9% for MB and 53.2% for RhB was obtained with only 15 mg of the photocatalyst. The degradation of MB occurred through N-demethylation and the formation of azure intermediates and degradation of RhB occurred through sequential deethylation and fragmentation of the xanthene ring, both in single and multicomponent systems. Full article

Water is one of the necessities for human survival, and clean water is essential for life. As a result, there is an increasing focus on efficient wastewater treatment methods, including advanced oxidation processes using innovative heterogeneous photocatalysts. In this context, TiO₂–graphene oxide (TGO) composites offer a multifaceted approach to wastewater treatment, combining the photocatalytic properties of TiO₂ with the adsorption capabilities and potential synergistic effects of graphene oxide. In this research, we intimately mixed commercial TiO₂ powder with graphene oxide at different concentrations (9, 16, and 25 wt.%) by exploiting sonochemical activation. The morphological and physicochemical analyses confirmed the interfacial interactions and the successful formation of the composite. The TGO composites exhibited increased reactivity compared to both GO and TiO₂ phases, during the photodegradation process of Rhodamine B (RhB), serving as a reaction model. Therefore, the photocatalytic results demonstrated the synergistic effect that occurs when a TiO₂-based photocatalyst is combined with sonochemically activated GO. The Cu²⁺ adsorption tests, simulating the removal of heavy metals from contaminated water, revealed that TGO composites displayed intermediate capabilities compared to the pure phases’ higher (GO) and lower (TiO₂) adsorption capacity. The functional characterizations revealed that the optimal design is represented by the sample containing 16 wt.% of GO. Overall, this study confirms that TGO composites are effective as photocatalysts and adsorbents for removing both organic and inorganic pollutants, making them strong candidates for wastewater treatment. Full article

Durable polyamidoamine (PAA) coatings were covalently grafted onto cotton by applying a water-soluble, glycine-based PAA (M-GLY) through a radical polymerization mechanism. M-GLY oligomers of different chain lengths, terminated with bisacrylamide groups, were synthesized via polyaddition of N,N′-methylenebisacrylamide and glycine at molar ratios of 1:0.9, 1:0.85, and 1:0.8. Cotton strips were then impregnated with differently concentrated (10 and 20 wt.%) aqueous solutions of the M-GLY oligomers in the presence of potassium persulfate, which oxidized cellulose and generated radicals that initiated polymerization of the M-GLY terminals, thereby enabling covalent grafting onto cotton. This process yielded M-GLY-grafted cotton (COT-g-M-GLY) with 2–15% add-on levels. Scanning electron microscopy revealed uniform surface coverage and penetration of the coating into fiber interiors. Grafting did not alter cellulose crystallinity—65% vs. 64% for grafted and virgin cotton. However, thermogravimetric analysis showed that COT-g-M-GLY exhibited lower thermo-oxidative stability than M-GLY-adsorbed cotton (COT/M-GLY) at similar add-ons. Flame-retardancy tests indicated that COT-g-M-GLY reduced the burning rate (by 10% to 30%) but did not achieve self-extinguishing behavior, unlike COT/M-GLY. Despite this, COT-g-M-GLY provided good protection against UV-induced photodegradation. After accelerated UVA–UVB exposure, cotton samples with 10% M-GLY add-on showed a significantly reduced yellowing rate compared to untreated cotton, as confirmed by spectrophotometric analysis. Full article

This study aims to demonstrate the feasibility of the use of chestnut waste as a green and circular material for developing iron-based photocatalysts for non-steroidal anti-inflammatory drug (NSAID) photodegradation. Four Fe-based catalysts and two pristine biochars were obtained upon a pyrolysis process at 500 and 700 °C and fully characterised. Due to the applied synthesis, iron is present in the form of isotropic grains of magnetite (Fe₃O₄), quite homogeneously dispersed onto the biochar. The textural properties of all the materials are mainly determined by the pyrolytic temperature, which results in macroporous materials at 500 °C and microporous ones at 700 °C. Fe-based catalysts were tested in Diclofenac (DFC) photodegradation. DFC removal was the result of both adsorption and photocatalytic reactions. Despite the good yield in DFC removal (80–100%), the formation of degradation by-products can partially invalidate the good effectiveness of this approach. However, the encouraging results of this study represent a step forward for the possible development of waste-derived biochar-based catalysts for in-field application. Full article

Both tungsten trioxide (WO₃) nanosheet arrays and tungsten trioxide/zinc oxide (WO₃/ZnO) nanocomposites were grown on fluorine-doped tin oxide (FTO) coated glass slides using a hydrothermal method to develop a visible-light-driven photocatalyst with easy reusability. Field emission scanning electron microscopy (FE-SEM) observations confirmed the formation of irregular oxide nanosheet arrays on the FTO surfaces. X-ray diffraction (XRD) analysis revealed the presence of hexagonal WO₃ and wurtzite ZnO crystal phases. UV-Vis diffuse reflectance spectroscopy showed that integrating ZnO nanostructures with WO₃ nanosheets resulted in a blue shift of the absorption edge and a reduced absorption capacity in the visible-light region. Photoluminescence (PL) spectra indicated that the WO 0.5/ZnO 2.0 sample exhibited the lowest electron-hole recombination rate among the WO₃/ZnO nanocomposite sample. Photocatalytic degradation tests demonstrated that all WO₃/ZnO nanocomposite samples had higher photodegradation rates for a 10 ppm methylene blue (MB) aqueous solution under visible-light irradiation compared to pristine WO₃ nanosheet arrays. Among them, the WO 0.5/ZnO 2.0 sample showed the highest photocatalytic efficiency. Furthermore, it exhibited excellent recyclability and high photodegradation stability over three cycles. Full article

The present work examines pure and palladium photofixed TiO₂ and binary (TiO₂/ZnO) photocatalysts for breaking down tartrazine, a food coloring agent, in distilled water. Powders with the following compositions are obtained using the sol-gel process: 100TiO₂, 10TiO₂/90ZnO, 50TiO₂/50ZnO, and 90TiO₂/10ZnO. The composite materials are analyzed using SEM-EDS, UV-Vis, DTA-TG, and X-ray diffraction. The synthesized gels are then photo-fixed with UV light to incorporate palladium ions and are also examined for tartrazine (E102) degradation. The photocatalytic tests were carried out in a cylindrical glass reactor illuminated by ultraviolet light. Compared to mixed binary catalysts, the prepared pure TiO₂ catalyst demonstrated greater activity in the photodegradation of tartrazine (E102). The further of a specific quantity of zinc oxide reduced the catalytic properties of TiO₂. The recombination of photoinduced electron-hole pairs in ZnO may account for this. In comparison to the pure samples, the co-catalytic palladium-modified gels exhibited higher photocatalytic efficiency. Heterojunction and palladium modification of the composites partially captured and transferred the electrons. Consequently, the longer lifetime of the photogenerated charges improved the catalytic activity of the palladium titanium dioxide and binary gels. Additionally, under UV light, pure and palladium photofixed TiO₂ and binary sol-gel samples displayed excellent stability for tartrazine photodegradation. Full article

Ferrous oxalate dihydrate (α-FOD) was synthesized from Ecuadorian black sands for phenol removal from aqueous solutions. Visible light-driven photodegradation kinetics were studied by varying the initial pollutant concentration, solution pH, and α-FOD dosage and by adding peroxydisulfate (PDS), including quenching tests. A representative model of phenol photodegradation was obtained by the Langmuir–Hinshelwood mechanism over a large range of concentrations (apparent kinetic constant, k = 0.524 h⁻¹). Almost complete removal was reached within 1 h under dark + 9 h under visible irradiation. The degradation rate was slightly affected by pH in the range of 3 to 9, with a significant improvement at pH 11 (k = 1.41-fold higher). The optimal α-FOD dosage was ~0.5 g/L. Two regimes were observed when using PDS: first, a heterogeneous Fenton-like process during the first few minutes after PDS addition; second, pure photocatalysis to completely remove the phenol. When comparing the two systems, without and with PDS, the half-life time for pure photocatalysis was 2.5 h (after the lamp was switched on). When adding PDS (1.0 mM), the half-life time was reduced to a few minutes (5 min after PDS addition, phenol removal was 66%). The photocatalyst presented remarkable degradation efficiency up to five repeated cycles. Full article

UiO-type Zr-BDC MOFs have garnered the interest of the scientific community due to their exceptional diversity in composition, structure, and chemical environment, as well as their high thermal and chemical stabilities. This work demonstrates the sustainable synthesis of a series of nanocrystalline/semicrystalline UiO-66(Zr) metal–organic frameworks (MOFs) under facile conditions—specifically at room temperature, in water, with high yield, and without the use of modulators or toxic byproducts. The synthesis involves either deprotonating the linker or utilizing various ratios of water and DMF as solvents. The as-prepared materials obtained from both synthesis strategies share key structural features with conventional UiO-66(Zr) in their short- and medium-range physicochemical properties, while exhibiting significant differences in crystallinity and textural properties. Nonetheless, the materials generally lack long-range order (semicrystalline), in particular these synthesized following the deprotonation strategy. However, the materials prepared using mixed solvent strategy seem to exhibit characteristics of nanocrystalline UiO-66(Zr). Overall, both approaches successfully addressed various synthesis challenges related to the highly sought-after Zr-based metal–organic frameworks (MOFs). Some of these MOF materials were tested for the photodegradation of rhodamine B (RhB) under mercury light irradiation, evidencing high photocatalytic efficiency of up to 75 ± 0.078% within 120 min under the pseudo-first-order model. This suggests an interaction between the photocatalyst and the RhB dye, involving electron injection from RhB and the ability for ligand-to-metal charge transfer (LMCT), which enhances the efficient photocatalytic degradation of RhB. The trapping experiments indicated that superoxide radicals (•O₂⁻) and photogenerated holes (h⁺) are crucial in the photodegradation of RhB. Moreover, the materials showed good recyclability across five tested cycles. A plausible photocatalytic reaction mechanism has been proposed to explain these findings. Full article

This study investigated the photocatalytic degradation of chlorothalonil under a range of ultraviolet lamp configurations, and studied the improvement in the photocatalytic degradation efficiency of a reflective material (silver-white aluminium foil). Increasing the number of UV lamps significantly enhanced degradation efficiency, reducing the half-life from 29.95 min with one lamp to 8.15 min with four in a 20 cm enamel bucket. The use of silvery-white aluminium foil further decreased the half-life to 3.86 min, improving degradation rates by up to 262.9%. In larger containers, degradation efficiency increased by up to 414.7% with aluminium foil. Comparisons with black aluminium foil confirmed that silver-white aluminium foil enhanced degradation by reflecting and redistributing UV light, increasing intensity by 252% and reducing the CTL half-life from 150.36 min to 22.9 min in a controlled light box. Further tests confirmed that silver-white aluminium foil amplified UV irradiation, increasing degradation efficiency by up to 555.1%. These improvements might suggest that aluminium foil enhances UV utilisation through direct reflection, refraction, and diffuse reflection, effectively redirecting photons that would otherwise escape the system. Experiments with natural water sources showed similar trends, with half-lives of 55.23 min in ultrapure water, 12.63 min in pond water, and 16.36 min in paddy field water. The addition of silver-white aluminium foil further reduced these times to 23.92 min, 7.13 min, and 12.34 min, respectively. These findings demonstrate that silvery-white aluminium foil significantly enhances CTL photodegradation without increasing energy consumption. While effective, the method faces challenges in acidic or alkaline wastewater due to potential corrosion of system components. Future research should focus on identifying stable, high-reflectivity materials for long-term applications. This study offers practical insights into the optimisation of photodegradation processes, which contributes to improved water treatment strategies and environmental pollution mitigation. Full article

Efficient plant biomass utilization is a key component in advancing a sustainable and circular bioeconomy. ZnO nanoparticle synthesis using plant extracts is actively studied as a part of this effort. Here, green ZnO nanoparticles were prepared using Licania tomentosa Benth (also known as Oiti) leaf extract. Characterization of the produced green ZnO nanoparticles (NPs) involved X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and UV–Visible spectroscopy (UV-Vis) techniques. Furthermore, we investigated photocatalytic degradation of the crystal violet (CV) dye catalyzed by the obtained ZnO NPs and evaluated the efficiency of the photodegradation process. The synthesized nanoparticles have an average crystallite size of 12.4 nm, as measured by XRD and have a spherical shape as revealed by SEM. UV–Vis studies show that ZnO nanoparticles have a relatively small band gap of 2.75 eV, as estimated by Tauc plot. The photodegradation activity tests using synthesized green ZnO NPs showed that approximately 79% of CV dye is decomposed in 2 h after being exposed to UV irradiation under experimentally studied conditions. The photodecomposition of CV is impacted by different factors, such as the catalyst bandgap and loading, the pH and the intensity of light. Moreover, an optimum photocatalyst loading was determined. Our studies reveal that Oiti leaf extract can be efficiently used for ZnO NPs synthesis, which has significant potential for photodegradation applications. Full article

Ofloxacin is one of the most commonly used antibacterial substances in the world. Like most medicines, it ends up in the environment through municipal sewage and undergoes various transformations, e.g., photodegradation. The aim of this study was an extensive analysis of ofloxacin photodegradation in both pure antibiotic and a commercial eye drop forms. In this study, a sunlight simulator, chromatographic methods of quantitative and qualitative determination, and biological methods for the evaluation of toxicity (Microbial Assay for Risk Assessment (MARA), Microtox^® and Spirotox) were used. The results showed that ofloxacin decomposed almost completely over 2 h of irradiation. Based on the high resolution mass spectrometry, 22 photoproducts were identified. The most sensitive strain of bacteria in the MARA test (Delftia acidovorans) responded at a concentration of 7.6 µg L⁻¹ of ofloxacin. The antibacterial activity of the irradiated samples was higher than that predicted based on the ofloxacin concentration. This suggests that the resulting photoproducts may have a bacteriostatic effect. The results of additional acute toxicity tests indicate the formation of toxic photoproducts, so it is reasonable to use other organisms that are not focused on a specific target. Such actions may allow for the capture of other, unexpected effects of formed photoproducts. Full article

Cd_xMn_1−xS solid solutions were synthesized by incorporating Mn²⁺ into CdS and the optimal ratio of Mn²⁺ to Cd²⁺ was explored via photocatalytic degradation performance for tetracycline (TC). Subsequently, the composite catalyst C@Cd_xMn_1−xS was prepared by loading Cd_xMn_1−xS onto the biomass gasification carbon residue (C) by hydrothermal method and characterized by various characterization tests. The optimal TC photodegradation condition and degradation mechanism catalyzed by C@Cd_xMn_1−xS was investigated. The results showed Cd_0.6Mn_0.4S had the optimal photocatalytic degradation efficiency, which is about 1.3 times that of CdS. The TC photodegradation efficiency by C@Cd_0.6Mn_0.4S prepared at the mass ratio of C to Cd_0.6Mn_0.4S of 1:2 was the best, which was 1.24 times that of Cd_0.6Mn_0.4S and 1.61 times that of CdS. Under the optimal conditions (visible light irradiation for 60 min, C@Cd_0.6Mn_0.4S of 20 mg, 40 mL TC solution of 40 mg/L), the TC degradation efficiency was 90.35%. The degradation efficiencies of 20 mg/L levofloxacin, ciprofloxacin, and 40 mg/L oxytetracycline catalyzed by C@Cd_0.6Mn_0.4S range from 89.88% to 98.69%. In the photocatalytic reaction system, •O₂⁻ and h⁺ are the dominant active species, which directly participate in the photocatalytic degradation reaction of TC, and •OH contributes little. The work provides a strategy to improve the photocatalytic performance of CdS for photocatalytic degradation antibiotics, and opens an interesting insight to deal with solid waste from biomass gasification. Full article

Among several types of emerging contaminants, the endocrine disruptors 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) are particularly notable. These compounds are discharged into sewage systems and subsequently into water bodies, as conventional wastewater treatment processes are unable to effectively eliminate such pollutants. Therefore, the present study aimed to evaluate the possibility of removing the endocrine disruptors 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) from water using the photocatalytic activity of the compound Ag₃AsO₄. Silver arsenate was synthesized and characterized, the quantification of the hormones E2 and EE2 was achieved by high-performance liquid chromatography with a fluorescence detector, and a validation process and some preliminary tests were performed on the photodegradation of the hormones using the Ag₃AsO₄ catalyst. Validation was performed, and satisfactory results were achieved: r = 0.9987 (E2), r = 0.9984 (EE2), a detection limit of 5.01 (E2) and 0.51 (EE2), a quantification limit of 15.19 (E2) and 1.54 (EE2), coefficients of variation for precision intraday and interday lower than 10.9725% and 11.3393%, respectively, and a recovery of 100.15% (E2) and 100.31% (EE2). In photodegradation studies, Ag₃AsO₄ showed different behavior in the presence of light for each hormone. In solution with E2, it reached a removal rate of 35% of the hormone under LED light, acting as a photocatalyst, while with EE2, it reached a removal rate of 96%; both results were obtained after 30 min of exposure to visible light. When this study is compared with other processes and materials, the high efficiency of the Ag₃AsO₄ photocatalyst in removing E2 and EE2, persistent emerging contaminants, becomes evident. This advancement has significant implications for wastewater treatment, offering a promising solution that can mitigate environmental impacts caused by endocrine disruptors. Full article

TNR@Ni-foam structures were prepared by an alkaline hydrothermal method in an autoclave in a strongly alkaline medium (10 M NaOH) at 150 °C with further acid washing (0.1 M HNO₃) and a second hydrothermal treatment in an autoclave at 180 °C. Two TiO₂ samples were used for preparation: anatase and P25 of mixed anatase and rutile phases. After the first step of hydrothermal treatment, a layered titanate structure was obtained (Na₂Ti₃O₇). Acid washing caused the substitution of Na⁺ by H⁺ and launched the formation of TNR. After the second hydrothermal treatment at 180 °C, for the optimal quantity of acid used for washing (10 mL per 0.75 g of TiO₂), titania was crystallized to an anatase phase with small quantities of brookite and rutile. The structures obtained from P25 exhibited more brookite and rutile than those based on the anatase precursor. The morphology of TNR@Ni-foam structures was observed by SEM. The obtained composites were tested for acetaldehyde photodegradation (240 ppm in air) during the continuous flow of gas (5 mL/min) through the reactor coupled with FTIR. The most active samples were those obtained from P25, which had a crystalline structure of TiO₂ and contained the lowest quantity of residue Na species. Full article