Phosphoric Acid Research Articles

The effect of different conditioning agents on dentin roughness and collagen structure

ObjectivesTo assess the impact of various organic and inorganic acids on the roughness, demineralization, and collagen secondary structures of human dentin and to compare these effects with those of traditional agents, specifically phosphoric acid (PA) and ethylenediaminetetraacetic acid (EDTA). MethodsCoronal dentin discs (n = 10) were examined by optical profilometry (roughness) and ATR-FTIR before and after conditioning with 32 % PA, 3 % nitric acid (NA), 20 % citric acid (CA), 20 % phytic acid (IP6) or 17 % EDTA. Spectra data were processed to quantify dentin demineralization (DM%) and percentage area of amide I curve-fitted components of β-turns, 310-helix, α-helix, random coils, β-sheets, and collagen maturation index. Statistical analysis was performed by one-way ANOVA or Kruskal-Wallis for DM% and roughness parameters, and paired t-test/Wilcoxon test for amide I components at significance level set at α = 0.05. ResultsAll treatments resulted in increased roughness parameters, with the most significant changes occurring primarily with PA, while EDTA exhibited the least changes. DM% was NA>PA>IP6>CA>EDTA in a descending order. Regarding amide I components, NA demonstrated a significant reduction in β-turns, 310-helices, and α-helices and it increased β-sheets and random coils. PA resulted in reduction in β-turns and α-helices while it increased β-sheets. CA and EDTA did not cause significant changes. The collagen maturation index significantly increased only after IP6 treatment. ConclusionsThe effect on dentin roughness parameters, demineralization, and collagen secondary structures varied based on the type of dentin surface treatment. Clinical significanceUnderstanding the impact of acids on the intrinsic properties of dentin is clinically essential for gaining insights into how these effects influence adhesion to dentin, the long-term stability of resin-based restorations, and the success of remineralization therapies.

Sequential Steps for Purifying Wet Processed Phosphoric Acid for Producing a High-Tech Grade and Barium or Ammonium Phosphate Salts

Sequential Steps for Purifying Wet Processed Phosphoric Acid for Producing a High-Tech Grade and Barium or Ammonium Phosphate Salts

Electrosorption-driven selective thorium removal from radioactive wastewater with phosphate – Incorporated g-C3N4 electrode

This research introduces a novel approach for developing an improved method for removing thorium ions (Th(IV)), termed as electrosorption, by fusing the principles of electricity and adsorption. The methodology involves utilizing a phosphate – incorporated graphitic carbon nitride (g-C3N4/P) electrode, synthesized via a hydrothermal – calcination process with urea as a precursor and bis (2-ethylhexyl) phosphoric acid (D2EHPA) as a dopant. Static batch experiments were conducted to explore the influence of various parameters, including voltages, initial Th(IV) concentrations and operational time, on the electrosorption of Th(IV). Characterization analysis including XRD, FT-IR, FESEM-EDS and XPS were conducted to validate the successful integration of phosphate into the g-C3N4 structure. The g-C3N4/P electrode demonstrated impressive adsorption capacity for Th(IV) electrosorption in an aqueous solution containing an initial concentration of Th(IV) at 100 mg.L−1. It was observed that applying a potential as low as −0.2 V resulted in significantly increase in the Th(IV) removal with 92.23 % (> 300 mg.g−1) within 30 minutes of duration, compared to cases without the electrochemical assistance (65.41 mg.g−1). Through FT-IR and XPS analyses, the adsorption mechanism was clarified as follows: (1) the negatively charged g-C3N4/P electrode attracted Th(IV) ions through electrostatic interaction; and (2) Th(IV) ions was coordinated with exposed oxygen (O), nitrogen (N) and phosphorus (P) atoms via complexation. In the context of real wastewater scenarios involving rare earth residue, encompassing Ce(III), La(III), Nd(III) and Pr(III) ions, the g-C3N4/P electrode showcased good capabilities in selectively adsorbing Th(IV). Additionally, the electrode synthesized in this study displayed considerable regenerative capabilities, sustaining a commendable removal ratio of approximately 70 % over five successive cycles. These findings underscore the promising potential of g-C3N4/P electrode for thorium removal through electrosorption applications.

Shear Bond Strength of Orthodontic Brackets Bonded with Thermo-Cured Glass-Based Materials-An In Vitro Study.

The results of orthodontic therapy largely depend, among other factors, on the preparation of the tooth enamel itself and the choice of material used to bond orthodontic brackets. The aim of this in vitro study was to determine the shear bond strength (SBS) and adhesive remnant index (ARI) score of thermo-cured glass-ionomers on different pretreated enamel, in comparison with the commonly used composite cement. Three commercially available nano-ionomer or highly viscous glass-ionomer cements (EQUIA Forte® Fil, EQUIA Fil, Ketac Universal) and two types of compo-sites (Heliosit Orthodontic, ConTec Go!) were investigated in this study. The research involved two hundred human premolars. The teeth were cleaned and polished, then randomly divided into five groups according to the enamel preparation method and the type of material. The enamel was treated in three different ways: polyacrylic acid, phosphoric acid, 5% NaOCl + etching with phosphoric acid, and a control group without treatment. Glass-ionomer cement was thermo-cured with heat from a polymerization unit during setting. Statistical analysis was performed using a Chi-square test and one-way ANOVA for independent samples. Spearman's Rho correlation coefficient was used to examine the relationship. Regardless of the material type, the results indicated that the weakest bond between the bracket and tooth enamel was found in samples without enamel pretreatment. The majority of the materials stayed on the brackets in samples without enamel preparation, according to ARI scores. The study's findings demonstrated that the strength of the adhesion between the bracket and enamel is greatly influenced by enamel etching and glass-ionomer thermo-curing. Clinical investigations would be required to validate the outcomes.

Development and optimization of high-performance extraction chromatography method for separation of rare earth elements

The effectiveness of commonly used extractants for chromatographic separation of rare earth elements (REEs) was compared. Columns loaded with similar molar concentrations of tributyl phosphate (TBP), di-(2-ethylhexyl) phosphoric acid (HDEHP), and N-Methyl-N, N, N-tri-octyl-ammonium chloride (Aliquat-336), with mineral acid as eluent were evaluated. Retention factors were determined, and separation efficiency was assessed based on the resolution data of the REEs acquired under the same elution conditions for each column. HDEHP demonstrated the best separation efficiency for the entire REE series (mean Rs = 2.76), followed by TBP (mean Rs = 1.52), while Aliquat-336 exhibited the lowest performance (mean Rs = 1.42). The HDEHP-coated column was then used to optimize the extraction chromatographic separation of the REEs. The primary challenge was to completely elute the heavy REEs (Tb – Lu) while maintaining adequate separation of the light REEs (La – Gd) within a reasonably short time. The stepwise gradient elution procedure improved the resolution between adjacent REEs, allowing the complete separation of the entire REE series within 25 minutes. Better separation efficiency for light REEs was achieved at higher column temperatures and a mobile phase flow rate of 1.5 mL/min in the tested domain of 20–60 °C, and 0.5–2.0 mL/min, respectively, resulting in plate heights (H) ranging from 0.011 to 0.027 mm.

Self-Organization of Polyurethane Ionomers Based on Organophosphorus-Branched Polyols.

Based on organophosphorus branched polyols (AEPAs) synthesized using triethanolamine (TEOA), ortho-phosphoric acid (OPA), and polyoxyethylene glycol with MW = 400 (PEG), vapor-permeable polyurethane ionomers (AEPA-PEG-PUs) were obtained. During the synthesis of AEPAs, the reaction of the OPA etherification with polyoxyethylene glycol was studied in a wide temperature range and at different molar ratios of the starting components. It turned out that OPA simultaneously undergoes a catalytically activated etherification reaction with triethanolamine and PEG. After TEOA is fully involved in the etherification reaction, excess OPA does not react with the terminal hydroxyl groups of AEPA-PEG or the remaining amount of PEG. The ortho-phosphoric acid remaining in an unreacted state is involved in associative interactions with the phosphate ions of the AEPA. Increasing the synthesis temperature from 40 °C to 110 °C leads to an increase in OPA conversion. However, for the AEPA-PEG-PU based on AEPA-PEG obtained at 100 °C and 110 °C, ortho-phosphoric acid no longer enters into associative interactions with the phosphate ions of the AEPA. Due to the hydrophilicity of polyoxyethylene glycol, the presence of phosphate ions in the polyurethane structure, and their associative binding with the unreacted ortho-phosphoric acid, the diffusion of water molecules in polyurethanes is enhanced, and high values of vapor permeability and tensile strength were achieved.

Organocatalytic Csp2-O Amination of Quinolin-4(1H)-ones with 3-Alkynyl-3-hydroxyisoindolinones.

The Brønsted acid catalytic Csp2-O amination of quinolin-4(1H)-ones with 3-alkynyl-3-hydroxyisoindolinones as animation reagents has been developed. The cascade dehydration/conjugate addition/intramolecular annulation/ring-opening reaction proceeded smoothly to afford a broad scope of aminated products with high efficiency. Furthermore, the enantioselective construction of Csp2-N atropisomers was also investigated in the presence of chiral phosphoric acid. Importantly, this work not only realized the organocatalytic Csp2-O amination of quinolin-4(1H)-ones but also laid the foundation for directly asymmetric synthesis of Csp2-N atropisomers.

Chiral phosphoric acid-catalyzed asymmetric epoxidation of alkenyl aza-heteroarenes using hydrogen peroxide

The synthesis of chiral α-azaheteroaryl oxiranes via enantioselective catalysis is a formidable challenge due to the required complex stereoselectivity and diverse N-heterocyclic structures. These compounds play a crucial role in developing bioactive molecules, where precise chirality significantly influences biological activity. Here we show that using chiral phosphoric acid as a catalyst, our method efficiently addresses these challenges. This technique not only achieves high enantio- and diastereoselectivity but also demonstrates superior chemo- and stereocontrol during the epoxidation of alkenyl aza-heteroarenes. Our approach leverages a synergistic blend of electrostatic and hydrogen-bonding interactions, enabling the effective activation of both substrates and hydrogen peroxide. The resulting chiral oxiranes exhibit enhanced diversity and functionality, aiding the construction of complex chiral azaaryl compounds with contiguous stereocenters. Kinetic and density functional theory studies elucidate the mechanism, highlighting chiral phosphoric acid’s pivotal role in this intricate enantioselective process.

Enabling extreme low-temperature proton pseudocapacitor with tailored pseudocapacitive electrodes and antifreezing electrolytes engineering

A critical current challenge in the development of proton pseudocapacitors is developing antifreezing electrolytes and high-performance proton storage materials in extreme environments. Here, we design an antifreezing proton pseudocapacitor using a high-concentration phosphoric acid electrolyte and pseudocapacitive electrode materials, which delivers an outstanding rate capacity and cycle life below − 40 °C. Comprehensive physical characterization techniques and theoretical simulations demonstrate that the solvation structure of the electrolyte defines the freezing point and electrochemical stability window, which is crucial for achieving fast charge carrier mobility and avoiding side effects. The pseudocapacitive hydrated tungsten oxide anodes and Prussian blue analogue cathodes with their open crystal structures achieve fast proton transport and storage, resulting in excellent electrochemical performance from − 60 to 25 °C (1000 cycles with no capacity fading at − 40 °C). Benefiting from the synergistic effect between the electrolyte and electrode materials, the fabricated proton pseudocapacitors exhibit remarkable low-temperature electrochemical performance. It achieves a maximum energy density of 39 Wh kg−1 and a broadened electrochemical window from 1.7 V at 25 °C to 2.3 V at − 60 °C. This work provides a comprehensive strategy to develop high-performance proton energy storage devices under ultralow-temperature conditions.

Assessment and Mitigation of Groundwater Contamination from Phosphate Mining in Tunisia: Geochemical and Radiological Analysis

Groundwater contamination in the Mediterranean Basin is a severe problem that has a significant impact on environmental ecosystems and human health. The unconventional uranium and the potentially toxic elements (PTEs) of phosphate rocks are the principal contaminants in the phosphate mining industry in Tunisia. Phosphogypsum (PG) results from the valorization of phosphate to fertilizers and phosphoric acid. PG stocks can be used in cement production, brick manufacturing, and soil amendments in desertic land, and can be resolved by using nanomaterial adsorbents. In the flat area of the study area, the increase in radioactivity (40K) is due to abusive fertilizer use. Geochemical and radiological analyses in the northern part of Tunisia and its karst shallow aquifer indicate significant contamination levels. The northern part exhibits moderate contamination, whereas the karst shallow aquifer shows higher contamination levels, particularly with elevated nitrate concentrations. In the phosphate basin, both washing phosphate and phosphogypsum reveal high levels of radioactive elements, with the latter showing especially high concentrations of radium. The shallow aquifer in this region has moderate contamination levels, while the deep geothermal aquifer also shows noticeable contamination but to a lesser degree compared to the shallow aquifer. The shallow groundwater is characterized by a higher value of radioactivity than the groundwater due to the contamination impact from the phosphate industry and the cumulative radioactivity disintegration. Finally, the nanoparticles and the electrostatic adsorption can decrease the PTEs and radionuclides from the contaminated water in the study area. Moreover, other key issues for advancing research on groundwater contamination are proposed in this study. It is time to valorize this PG and the other mines of (Fe, Pb, and Zn) in the socioeconomic sector in Tunisia and to minimize the environmental impact of the industrial sector’s extraction on groundwater and human health in the study area.

A Simple Validated LC-UV Method for the Simultaneous Determination of Brimonidine and Brinzolamide in the Presence of Brinzolamide's Degradation Product (Major Metabolite) in Rabbit Aqueous Humor.

A sensitive, specific, reliable and low-cost LC-UV method has been developed and validated for simultaneous quantification of brimonidine tartrate (BM) and brinzolamide (BZ) in rabbit aqueous humor (AH) in the presence of N-desethyl-brinzolamide (NDBZ); BZ is a major degradation product, and it is also considered to be its major metabolite. Dorzolamide hydrochloride (DZ) was used as an internal standard (IS). The analytes were extracted from rabbit AH samples by a simple pre-treatment utilizing ZnSO4.7H2O as a deproteinizing agent. The analytes were separated on a cyanopropyl Waters column (4.6 × 200mm, 5μm) with an isocratic mobile phase consisting of 25mM ammonium acetate pH4.5 (adjusted with 85% phosphoric acid):methanol:acetonitrile (94:4.5:1.5, v/v) at a flow rate of 1.0mLmin-1. The detection was done at 254nm. The lower limit of quantification in rabbit AH was 100.0ngmL-1. The method was validated according to EMA guidelines. The method was confirmed to be accurate, precise and linear over a range of 100.0-1000.0ngmL-1 for BM and BZ. The method developed herein is simple, safe, eco-friendly, rapid and accurately applied for the quantification of BM and BZ, along with the successful separation of NDBZ, which is considered as a potential irritant degradation product of BZ.

Effect of Water-Soluble Polymers on the Rheology and Microstructure of Polymer-Modified Geopolymer Glass-Ceramics.

This work explores the effects of rigid (0.1, 0.25, and 0.5 wt. %) and semi-flexible (0.5, 1.0, and 2.5 wt. %) all-aromatic polyelectrolyte reinforcements as rheological and morphological modifiers for preparing phosphate geopolymer glass-ceramic composites. Polymer-modified aluminosilicate-phosphate geopolymer resins were prepared by high-shear mixing of a metakaolin powder with 9M phosphoric acid and two all-aromatic, sulfonated polyamides. Polymer loadings between 0.5-2.5 wt. % exhibited gel-like behavior and an increase in the modulus of the geopolymer resin as a function of polymer concentration. The incorporation of a 0.5 wt. % rigid polymer resulted in a three-fold increase in viscosity relative to the control phosphate geopolymer resin. Hardening, dehydration, and crystallization of the geopolymer resins to glass-ceramics was achieved through mold casting, curing at 80 °C for 24 h, and a final heat treatment up to 260 °C. Scanning electron microscopy revealed a decrease in microstructure porosity in the range of 0.78 μm to 0.31 μm for geopolymer plaques containing loadings of 0.5 wt. % rigid polymer. Nano-porosity values of the composites were measured between 10-40 nm using nitrogen adsorption (Brunauer-Emmett-Teller method) and transmission electron microscopy. Nanoindentation studies revealed geopolymer composites with Young's modulus values of 15-24 GPa and hardness values of 1-2 GPa, suggesting an increase in modulus and hardness with polymer incorporation. Additional structural and chemical analyses were performed via thermal gravimetric analysis, Fourier transform infrared radiation, X-ray diffraction, and energy dispersive spectroscopy. This work provides a fundamental understanding of the processing, microstructure, and mechanical behavior of water-soluble, high-performance polyelectrolyte-reinforced geopolymer composites.

Accelerating Anhydrous Proton Transport in Covalent Organic Frameworks: Pore Chemistry and its Impacts.

Proton conduction is important in both fundamental research and technological development. Here we report designed synthesis of crystalline porous covalent organic frameworks as a new platform for high-rate anhydrous proton conduction. By developing nanochannels with different topologies as proton pathways and loading neat phosphoric acid to construct robust proton carrier networks in the pores, we found that pore topology is crucial for proton conduction. Its effect on increasing proton conductivity is in an exponential mode other than linear fashion, endowing the materials with exceptional proton conductivities exceeding 10-2 S cm-1 over a broad range of temperature and a low activation energy barrier down to 0.24 eV. Remarkably, the pore size controls conduction mechanism, where mesopores promote proton conduction via a fast-hopping mechanism, while micropores follow a sluggish vehicle process. Notably, decreasing phosphoric acid loading content drastically reduces proton conductivity and greatly increases activation energy barrier, emphasizing the pivotal role of well-developed proton carrier network in proton transport. These findings and insights unveil a new general and transformative guidance for designing porous framework materials and systems for high-rate ion conduction, energy storage, and energy conversion.

The Synthesis and Characterization of Selenium-Doped Bioglass.

Background Bioactive glass, which can form strong bonds with tissues, particularly bones, has become pivotal in tissue engineering. Incorporating biologically active ions like selenium enhances its properties for various biomedical applications, including bone repair and cancer treatment. Selenium's antioxidative properties and role in bone health make it a promising addition to biomaterial. Aim The present study was aimed at the preparation and characterization of selenium-doped bioglass. Materials and methods Tetraethyl orthosilicate (TEOS) was mixed with ethanol, water, and nitric acid to form a silica network and then supplemented with calcium nitrate, selenium acid sodium nitrate, and orthophosphoric acid. Sequential addition ensured specific functionalities. After sintering at 300 °C for three hours, the viscous solution transformed into powdered selenium-doped bioglass. Characterization involved scanning electron microscope (SEM) for microstructure analysis, attenuated total reflection infrared spectroscopy (ATR-IR) for molecular structure, and X-ray diffraction (XRD)for crystal structure analysis. Results SEM analysis of selenium-doped bioglass reveals a uniform distribution of selenium dopants in an amorphous structure, enhancing bioactivity through spherical particles with consistent size, micro-porosity, and roughness, facilitating interactions with biological fluids and tissues. ATR-IR analysis shows peaks corresponding to Si-O-Si and P-O bonds, indicating the presence of phosphate groups essential for biomedical applications within the bioglass network. XRD analysis confirms the amorphous nature of selenium-doped bioglass, with shifts in diffraction peaks confirming selenium incorporation without significant crystallization induction. Conclusion The selenium-infused bioglass displays promising versatility due to its amorphous structure, potentially enhancing interactions with biological fluids and tissues. Further research is needed to assess its impact on bone regeneration activity.

Phosphorus: Chronicles of the epistemology of a vital element.

It was in the philosopher's stone quest that the alchemist Hennig Brand isolated chemiluminescent white phosphorus (P), Greek for "light bearer", from urine in 1669. By 1771 phosphorus was isolated from bone, and in 1777 it was identified by Antoine Lavoisier as a highly reactive element that exists predominantly in nature as ionic phosphate (PO43-) and in solution as phosphoric acid (H3PO4). Early 20th century studies revealed phosphorylated biomolecules as essential components of replicative nuclear material (RNA, DNA), a metabolic source of energy (ATP), and structural components of cellular membrane (phospholipid bilayer). Life on earth began as organophosphates of a self-replicating RNA that evolved into DNA and acquired a membrane to form the original eukaryotes, which eventually joined to form multicellular organisms of the deep sea. Tissue mineralization during transition from the ocean to land generated the endoskeleton, the largest phosphorus stores of evolving vertebrates. Subsequent studies of phosphate homeostasis elucidated its complex regulatory system based on the interaction of the kidney, small intestine, bone, and parathyroid glands, orchestrated by hormones (PTH, calcitriol, FGF23, Klotho), and carried out by phosphate-specific transporters (SLC34 and SLC20 families) all to ensure adequate phosphate for survival and health. Paradoxically, kidney replacement therapy in the 1970s, by prolonging the lives of millions of individuals with kidney failure, revealed the hazards of phosphorus excess. "Phosphorus the light bearer" has become in the eyes of many nephrologists "Phosphorus the cardiovascular toxin".

Synthesis and evaluation of phosphoric ester pyrogallic acid hexaglycidyl ether as a green corrosion protective agent in the gas and oil industries

Synthesis and evaluation of phosphoric ester pyrogallic acid hexaglycidyl ether as a green corrosion protective agent in the gas and oil industries

Dynamics of Coordinated Phosphonate Group Directly Observed by 17O-NMR in Lanthanide(iii) Complexes of a Mono(ethyl phosphonate) DOTA Analogue.

Biological phosphates can coordinate metal ions and their complexes are common in living systems. Dynamics of mutual oxygen atom exchange in the tetrahedral group in complexes has not been investigated. Here, we present a direct experimental proof of exchange ("phosphonate rotation") in model Ln(III) complexes of monophosphonate H4dota analogue which alters phosphorus atom chirality of coordinated phosphonate monoester. Combination of macrocycle-based isomerism with P-based chirality leads to several diastereoisomers. (Non)-coordinated oxygen atoms were distinguished through 17O-labelled phosphonate group and their mutual exchange was followed by various NMR techniques and DFT calculations. The process is sterically demanding and occurs through bulky bidentate (κ2-PO2)- coordination and was observed only in twisted-square antiprism (TSA) diastereoisomer of large Ln(III) ions. Its energy demands increase for smaller Ln(III) ions (298ΔG≠(exp./DFT)=51.8/52.1 and 61.0/71.5 kJ mol-1 for La(III) and Eu(III), respectively). These results are helpful in design of such complexes as MRI CA and for protein paramagnetic NMR probes. It demonstrates usefulness of 17O NMR to study solution dynamics in complexes involving phosphorus acid derivatives and it may inspire use of this method to study dynamics of phosphoric acid derivatives (as e. g. phosphorus acid-based inhibitors of metalloenzymes) in different areas of chemistry.

Ethanol production from the wood and fruit juice of paper mulberry via simultaneous saccharification and juice co-fermentation under normal and very high gravity conditions

A novel batch simultaneous saccharification and juice co-fermentation (SSJcF) process was investigated using mixtures of PHP (phosphoric acid plus hydrogen peroxide) pretreated wood and fruit juice of paper mulberry tree. All the different substrate mixture configurations evaluated under normal gravity SSJcF (total sugar titer of 180 g/L) significantly improved both ethanol concentration and yield compared to sole simultaneous saccharification and fermentation (SSF) of paper mulberry wood. Among the different mixing ratios, the feedstock mixture with equal sugar content from each substrate resulted in maximum ethanol concentration, yield and productivity of 77.1 g/L, 83.9 % and 1.1 g/L/h, respectively. The external additions of mineral nutrients also had no impact on fermentation performance of the mixture. Furthermore, SSJcF was evaluated under different levels of high gravity (HG) and very high gravity (VHG) conditions. The total sugar titer of 350 g/L at equal contributions from each substrate reached very high ethanol concentration of 147.0 g/L, with yield and productivity of 82.3 % and 1.5 g/L/h, respectively. By implication, the PM wood and fruit juice mixture could serve as suitable low-cost and non-food feedstock alternative to the typical use of sugary and/or starchy feedstocks for VHG fermentation.

Investigation of phosphoric acid influence on the oxygen reduction reaction on carbon-supported platinum electrocatalyst via rotating disk electrodes

Phosphoric acid (PA), utilized as an electrolyte in high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs), has been observed to exert a detrimental effect on oxygen reduction reaction (ORR) electrocatalyst, consequently compromising cell performance. To comprehensively elucidate the impact of phosphoric acid on ORR, this study employs a range of electrochemical techniques, including electrochemical impedance spectroscopy and voltammetry method. The negative influence of PA on commercial Pt/C electrocatalyst manifests differently under various potentials and PA concentrations. Upon the introduction of PA, the decay rate and amplitude of ECSA, as calculated by Hupd adatoms, are notably smaller compared to the kinetic current density generated by the oxygen reduction reaction. Particularly, in the kinetic-controlled potential range, the negative impact of PA becomes more pronounced at higher electrode potentials, accompanied by a significantly steeper Tafel slope. Additionally, the EIS results suggest that phosphoric acid may gradually transform into polyphosphoric acid at a high concentration, accentuating the poisoning effect of PA under steady-state conditions. However, a high PA concentration can substantially alter the electrolyte properties, potentially leading to an inaccurate assessment of PA tolerance in electrocatalysts. Hence, it is imperative to consider the appropriate PA concentration when evaluating PA tolerance and to discern the poisoning mechanism under different electrode potentials.

Extraction and Purification of Squalene from Virgin Olive Oil via Catalytic Transesterification and Molecular Distillation

Squalene, a highly valuable compound abundant in various natural sources, shows great potential in pharmaceutical, cosmetic, and nutraceutical applications. This research article outlines a comprehensive methodology for extracting and purifying squalene from virgin olive oil, a rich source of the compound. The extraction process begins with degumming, which involves heating the olive oil to 60-70°C to reduce viscosity, followed by the addition of 2-3% warm water to hydrate phospholipids. Food-grade phosphoric acid is then added to react with the phospholipids, forming precipitates. The mixture is stirred for 20-30 minutes and allowed to rest for an additional 20-30 minutes, enabling impurities to settle. The upper layer of degummed oil is separated via decantation or centrifugation and washed with warm water for pH adjustment. Next, transesterification is performed by mixing 100 ml of virgin olive oil with 25% methanol (w/w) and a catalyst (0.5% sodium methoxide or PTSA), and heating the mixture to 80-90°C under reflux for 1-2 hours. Following transesterification, the solvent and acetone are distilled out, and acetone precipitation is repeated 2-3 times to remove unsaponified matter, which is then filtered and evaporated. The concentrated oil undergoes molecular distillation at 180°C and 0.0033 bar pressure for 1 hour, yielding the distillate and residue for further analysis. Qualitative analysis using Thin Layer Chromatography (TLC) involves Merck TLC plates with silica gel 60 F254 and a hexane: chloroform (9:1) mobile phase. Spots are developed with a 10% HCl solution, confirming the presence of squalene with an RF value of 0.93. Quantitative analysis via High-Performance Thin-Layer Chromatography (HPTLC) employs Merck TLC plates with cyclohexane as the mobile phase and CAMAG at 254 nm and 366 nm wavelengths, revealing a squalene purity of 67% and a recovery rate of 69.8%. The initial purification through transesterification facilitated the conversion of ester groups, yielding squalene-rich fractions, while acetone precipitation effectively removed saponified matter. Molecular distillation further enhanced squalene purity. TLC analysis confirmed the qualitative presence of squalene, and HPTLC provided precise quantitative measurements. The obtained squalene purity of 67% significantly enriches the initial content in virgin olive oil, though further optimization could enhance purity and yield. Complementary techniques like GC-MS or HPLC could validate the purification process. This study presents an efficient, replicable procedure for extracting and purifying squalene from virgin olive oil, with significant implications for pharmaceutical, cosmetic, and nutraceutical industries. The findings support a sustainable and ethical shift towards vegetable-derived squalene, meeting market demands while ensuring high-quality production.