Nitrogen Incorporated Photoactive Brownmillerite Ca2Fe2O5 for Energy and Environmental Applications

Investigating the activity of Ca2Fe2O5 additives on the thermochemical energy storage performance of limestone waste

Efficient and reliable energy storage systems are necessary to address the intermittency and variability of renewable energy sources. Thermochemical energy storage (TCES) has emerged as a promising solution for long-term renewable energy storage, with limestone being a widely studied material due to its abundance and high energy density. However, the practical implementation of limestone-based TCES systems faces challenges related to performance degradation upon multiple energy storage/release cycles, impacting their long-term viability and efficiency. In this study, we investigate the activity of Ca2Fe2O5 additives on the thermochemical energy storage performance of limestone waste. Ca2Fe2O5 additives were synthesized by a wet precipitation method using three different Ca/Fe molar ratios and added to limestone waste in a 5, 10, and 20 weight concentration. The synthesized samples were characterized using XRD, SEM, EDS, BET, and XPS techniques. The thermal properties and heat storage performance of the samples were evaluated through thermogravimetric analysis of calcination/carbonation cycling experiments. The results demonstrate the potential of Ca2Fe2O5 additives to improve the cycling stability and energy storage density of limestone-based TCES systems. The sample with 5 wt% of Ca2Fe2O5 additive having Ca : Fe molar ratio of 1 : 1 outperformed all samples with an effective conversion rate of 0.21 after 40 cycles, 1.31 times higher than limestone waste.

Acmella oleracea induced nanostructured Ca2Fe2O5 for evaluation of photo catalytic degradation of cardiovascular drugs and bio toxicity

Biosynthesis of nanoparticles is increasingly becoming popular due to the demand for sustainable technologies worldwide. In the present investigation, Acmella oleracea plant extract fuelled combustion technique followed by calcination at 600 °C was adopted to prepare nanocrystalline Ca₂Fe₂O₅. The prepared nano compound was characterised using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Ultra Violet (UV) spectroscopy, Infrared (IR) spectroscopy and its role was assessed for photocatalytic pollutant degradation along with bactericidal action in the concentration range of 1 μg/mL to 320 μg/mL. The photocatalytic degradation efficiency of pollutant drugs Clopidogrel Bisulphate and Asprin used for cardiovascular disorders is around 80% with 10 mg/L photocatalyst. The results showed that the photocatalytic activity increased with rising pH from 4, to 10, along with a significant antibacterial action against Enterococcus faecalis bacteria and a slight cytotoxic effect at high concentrations. The antibacterial property was reinforced by Minimum inhibitory concentrations (MIC) and Minimum bactericidal concentrations (MBC) studies with an average value of 0.103 at 600 nm which was further proved by significant anti-biofilm activeness. Adhesion tests in conjunction with cryogenic-scanning electron microscopy displayed a morphological change through agglomeration that caused an expansion in nano particles from 181 nm to 223.6 nm due to internalization followed by inactivation of bacteria. In addition, the non-toxicity of nano Ca₂Fe₂O₅ was confirmed by subtle cytological changes in microscopic images of Allium Cepa root cells in the concentration range 0.01-100 μg/mL and a slight inhibition in HeLa cell proliferation indicated by IC₅₀ value of 170.94 μg/mL. In total, the current investigation for the first time reveals the application of bio based synthesis of Nano Ca₂Fe₂O₅ to new possibilities in bioremediation namely degrading cardiovascular pharmaceutical pollutants, endodontic antibacterial action and cytological activity.

Integration of plasmonic AgPd alloy nanoparticles with single-layer graphitic carbon nitride as Mott-Schottky junction toward photo-promoted H2 evolution

Plasmonic AgPd alloy nanoparticles (AgPdNPs) decorated on single-layer carbon nitride (AgPdNPs/SLCN) for the designing of the Mott-Schottky junction were constructed with the ultrasonically assisted hydrothermal method and used toward photo evolution H2 from formic acid (FA) at near room temperature (30 °C). The Pd atom contains active sites that are synergistically boosted by the localized surface plasmon resonance (LSPR) effect of Ag atoms, leading to considerably enhanced photocatalytic properties. The photoactive AgPdNPs/SLCN obtained supreme catalytic activity to produce 50 mL of gas (H2 + CO2) with the initial turnover frequency of 224 h-1 under light irradiation. The catalyst showed stable catalytic performance during successive cycles.

Metallurgical Wastes as Resources for Sustainability of the Steel Industry

The industrial pollution caused by metallurgical waste accumulation has a negative impact on the three environmental factors: soil, air and water. Therefore, the correct management of these wastes would lead to: protection of the environmental factors, the saving of natural resources and sustainability of the steel industry. The purpose of this paper is to assess the chemical and mineralogical compositions of metallurgical wastes landfilled in the Păgida slag dump (Alba County, Romania), for sustainability of the steel industry and metal conservation. The chemical compositions of the two waste samples were analyzed by the XRF (X-ray fluorescence) technique. According to the chemical characterization, magnesium oxide (MgO) has potential to be used as an additional and raw material in the cement industry. The presence of oxides such as CaO, SiO2 FeO and Al2O3 in the compositions of the metallurgical waste samples indicate that they have the potential for use as clinker materials in cement production. The iron and manganese contents from metallurgical wastes can be reused in the iron and steel industry. The presence of V2O5 and TiO2 is connected with the making of stainless steel, and for this reason they have the potential to be reused in the stainless steel industry. The predominant chemical compounds are SiO2, Fetotal, Cao and MgO. The mineralogical compositions were analyzed by the XRD (X-ray diffraction) technique. The mineralogical compounds presenting reuse potential in different domains are Fayalite, Magnetite, Magnesioferrite and Periclase. The mineralogical compounds from metallurgical wastes can be reused as: raw and/or additional materials in the process from which they originate (steelmaking); raw and/or additional materials in road construction and concrete production; pigments in paints; micronutrients in fertilizers; ore of iron, etc. Then, the theoretical assessments of the recovery potentials of the metals were estimated for slag dumps. Copper (Cu), vanadium (V), molybdenum (Mo) and nickel (Ni) have high recovery potential. The total economic value of the recovery potential of metals from slag dumps was assessed to be USD 1175.7440 million.

Enhanced photo-fenton and photoelectrochemical activities in nitrogen doped brownmillerite KBiFe2O5

Visible-light-driven photo-fenton-like catalytic activity and photoelectrochemical (PEC) performance of nitrogen-doped brownmillerite KBiFe₂O₅ (KBFO) are investigated. The effective optical bandgap of KBFO reduces from 1.67 to 1.60 eV post N-doping, enabling both enhancement of visible light absorption and photoactivity. The photo-fenton activity of KBFO and N-doped KBFO samples were analysed by degrading effluents like Methylene Blue (MB), Bisphenol-A (BPA) and antibiotics such as Norfloxacin (NOX) and Doxycycline (DOX). 20 mmol of Nitrogen-doped KBFO (20N-KBFO) exhibits enhanced catalytic activity while degrading MB. 20N-KBFO sample is further tested for degradation of Bisphenol-A and antibiotics in the presence of H₂O₂ and chelating agent L-cysteine. Under optimum conditions, MB, BPA, and NOX, and DOX are degraded by 99.5% (0.042 min^-1), 83% (0.016 min^-1), 72% (0.011 min^-1) and 95% (0.026 min^-1) of its initial concentration respectively. Photocurrent density of 20N-KBFO improves to 8.83 mA/cm² from 4.31 mA/cm² for pure KBFO. Photocatalytic and photoelectrochemical (PEC) properties of N-doped KBFO make it a promising candidate for energy and environmental applications.

Persistent luminescence phosphor as in-vivo light source for tumoral cyanobacterial photosynthetic oxygenation and photodynamic therapy

Tumor oxygenation level has been regarded as an attractive target to elevate the efficiency of photodynamic therapy (PDT). Cyanobacterial photosynthesis-mediated reversal of tumor hypoxia could enable an oxygen-boosted PDT, but is limited by scant penetration depth and efficiency of external light. Herein, aiming at the dual purposes of reducing biological toxicity induced by long-term light irradiation and alleviating hypoxia, we here introduce a novel-designed CaAl₂O₄:Eu,Nd blue persistent luminescence material (PLM) as the in vivo light source after pre-excited in vitro. The ingenious construction of blue-emitting PLM with “optical battery” characteristics activates cyanobacterial cells and verteporfin simultaneously, which performs the successive oxygen supply and singlet oxygen generation without the long-term external excitation, resulting in the modulated tumor hypoxic microenvironment and enhanced photodynamic tumor proliferation inhibition efficiency. Both in vitro cellular assessment and in vivo tumor evaluation results affirm the advantages of self-produced oxygen PDT system and evidence the notable antineoplastic outcome. This work develops an irradiation-free photosynthetic bacteria-based PDT platform for the optimization of both oxygen production capacity and light utilization efficiency in cancer treatment, which is expected to promote the clinical progress of microbial-based photonic therapy.

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Construction of CaAl₂O₄:Eu,Nd PLM to generate ¹O₂ without the aid of exogenous light excitation.

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Cyanobacteria with light-triggered oxygenation effect were employed for the normalization of tumor microenvironment.

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A distinct exogenous “irradiation-free” cyanobacteria-based PDT platform was rationally engineered.

g-C3N4/Ca2Fe2O5 heterostructures for enhanced photocatalytic degradation of organic effluents under sunlight

g-C₃N₄/Ca₂Fe₂O₅ heterostructures were successfully prepared by incorporating g-C₃N₄ into Ca₂Fe₂O₅ (CFO). As prepared g-C₃N₄/CFO heterostructures were initially utilized to photodegrade organic effluent Methylene blue (MB) for optimization of photodegradation performance. 50% g-C₃N₄ content in CFO composition showed an enhanced photodegradation efficiency (~ 96%) over g-C₃N₄ (48.15%) and CFO (81.9%) due to mitigation of recombination of photogenerated charge carriers by Type-II heterojunction. The optimized composition of heterostructure was further tested for degradation of Bisphenol-A (BPA) under direct sunlight, exhibiting enhanced photodegradation efficiency of about 63.1% over g-C₃N₄ (17%) and CFO (45.1%). The photoelectrochemical studies at various potentials with and without light illumination showed significant improvement in photocurrent response for g-C₃N₄/Ca₂Fe₂O₅ heterostructures (~ 1.9 mA) over CFO (~ 67.4 μA). These studies revealed efficient solar energy harvesting ability of g-C₃N₄/Ca₂Fe₂O₅ heterostructures to be utilized for organic effluent treatment.