Phosphoric Acid Research Articles

Elaboration of Fibrous Structured Activated Carbon from Olive Pomace via Chemical Activation and Low-Temperature Pyrolysis

The objective of this study is to examine the preparation of activated carbon with a fibrous structure obtained from olive pomace through a chemical activation process using phosphoric acid (H3PO4) as the activating agent under air at a lower temperature. According to the findings, the most effective conditions to achieve high-performance activated carbon were 22 vol.% of H3PO4, a two-hour chemical activation impregnation residence time at 50°C, and a 500°C pyrolysis temperature for one hour. Structural analysis revealed that activated carbons possess highly developed textural and structural properties, resulting in an iodine value of 923 mg/g and a specific surface of 1400 m2/g. In addition to its microporosity, the produced carbon exhibits a highly developed fibrous structure, providing excellent adsorption properties. To confirm these results, SEM, FT-IR, XRF, XRD, Raman, and TGA techniques were employed. The fibrous carbon produced will expand the use of renewable carbon materials for removing various types of contaminants, including organic and inorganic pollutants in water, and numerous other industrial applications.

The role of Ni- and Cd-resistant rhizobacteria in promoting the growth of rice seedlings and alleviating the combined phytotoxicity of Ni and Cd

The problem of potentially toxic metal pollution is increasingly acute with the development of human society. In this study, we investigated the remediation of nickel (Ni) and cadmium (Cd) co-contamination through inoculating rice with three new-isolated Ni- and Cd-resistant plant growth-promoting rhizobacteria (PGPR) Y3, Y4, and Y5. These three strains possessed growth-promoting properties, including 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity, the ability of indoleacetic acid (IAA) production, phosphate solubilization, siderophores production, and exopolysaccharide (EPS) development. According to 16S rDNA sequence homology, strains Y3, Y4, and Y5 were identified as Pseudomonas sp., Chryseobacterium sp., and Enterobacter sp., respectively. Based on the results of rice germination experiments conducted under combined toxicity, we set the contamination concentrations for Ni2+ at 20μgmL-1 and Cd2+ at 40μgmL-1. Then we conducted potting experiments at these concentration levels to study the effects of strains Y3, Y4, and Y5 on rice growth under synergistic Ni and Cd stress. The results indicated that the inoculated strains Y3, Y4, and Y5 were effective in promoting the growth of rice seedlings under the combined stress of Ni and Cd, and conferring tolerance to Ni and Cd by increasing the antioxidant enzyme activities of the seedlings. Among them, strain Y3 exhibited stronger ACC deaminase activity, IAA production capacity, and EPS production capacity, showing the most pronounced growth-promoting effect on rice. It was demonstrated that after inoculation with strain Y3, the germination rate of rice seeds increased by 43%, the fresh weight of stems improved by 35%, and the chlorophyll content enhanced by 70% and other growth-promoting phenomena. Additionally, under Ni and Cd stress, strain Y5 performed better than strain Y4 in terms of IAA production capacity and its influence on rice root growth, suggesting that IAA production might play a specifically essential role in root growth under Ni and Cd stress.

Fabrication of sodium alginate doped phosphoric acid composite hydrogel and its application of the adsorption of La (III) in wastewater

Recycling rare earth ions from wastewater is an important task, as rare earth elements have a wide range of applications and can cause harm to the environment if discharged arbitrarily. In this work, a simple and inexpensive hydroxyethylidene diphosphate-based adsorbent (SA@HEDP) for adsorbing lanthanum was designed and fabricated. The adsorbent SA@HEDP with the surface rich in phosphate and hydroxyl functional groups provided active sites for adsorption of lanthanum. Research on adsorption performance was conducted by testing the amount of HEDP added, the amount of adsorbent used, the effect of initial pH of La (III), adsorption time, and temperature. The results showed that the adsorption capacity of the adsorbent was 158.0 mg/g. Adsorption of La (III) in real wastewater was tested, when the initial concentration of La (III) was 319.2 mg/L, it could be basically all recovered through three adsorption processes. SEM, EDS mapping, XPS, FTIR, and Zeta potential were used to characterize and analyze the mechanism, and mass transfer kinetics was used to analyze the adsorption process of the adsorbent for La (III).

Exploring the performance of Coriandrum Sativum extract as an effective corrosion inhibitor for mild steel in a [formula omitted]medium, and its sustainable application in the eco-friendly removal of heavy metals

This research investigated the performance of coriander seeds, for the first time, in two critical phenomena: wastewater treatment and corrosion inhibition in acidic environments. On one hand, the aqueous extracts from Coriandrum Sativum seeds (CE) were evaluated for mild steel corrosion inhibition in a 2.0M phosphoric acid medium using several techniques such as phytochemical analysis (GC-MS), potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy (SEM-EDAX) and theoretical analyses, including DFT calculations and Molecular Dynamic Simulations, further elucidated the major chemical components. First, the phytochemical analysis has proved that CE contains heteroatoms. Second, the electrochemical results indicate that CE behaves as a mixed type inhibitor and the corrosion reaction is controlled by charge transfer process. Finally, The theoretical calculations confirmed that the active compounds of CE can be adsorbed on the Fe (1 1 0) surface through physical patterns and by sharing charges with iron to form coordinate bonds. The acquired results have shown a strong correlation between corrosion inhibition efficiency that was about 93%, SEM-EDAX and DFT parameters. On the other hand, the study examined coriander seeds (CS) in powder form as a removal of copper ions in aqueous solutions through Atomic Absorption Spectroscopy and Inductively Coupled Plasma analysis. The parametric study was effectuated by establishing the effect of contact time, adsorbent mass, solution pH and stirring speed. The removal rate was about 79%. Regeneration studies showed that CS could be reused for five cycles without significant loss of effectiveness. SEM-EDAX analysis has proved the studied process.

Influence of Phosphoric Acid Activation on Physiochemical Characteristics of Activated Carbons and Their Performance as Supercapacitor

ABSTRACTWe investigate the influence of phosphoric acid (H3PO4) activation on physiochemical characteristics of activated carbons (ACs) as a function of number of activation steps such as two‐step and three‐step and impregnation ratio (IR). Scanning electron microscopy observations identified that different morphologies in the forms of graphene sheet‐like, nano‐granular, and flake‐like carbon structure in the cases of ACs. FTIR spectroscopy confirmed that successful incorporation of phosphorous group in the ACs by H3PO4 activation. X‐ray diffraction (XRD) profile exposed that irrespective of the activation method and IR, all AC samples showed narrow and sharp XRD crystalline peak along with the amorphous signals. Raman scattering analysis suggested that three‐step activation create more defective structure as compared to two‐step activation route. Nitrogen adsorption–desorption isotherm measurements indicated that upon fabricating ACs via three‐step and two‐step activation approach, around 6.5 times and 3‐fold enhancement in the value of surface area of ACs as compared to that of carbon before activation. In addition, higher the IR value, lower the textural properties of ACs. This study demonstrated that three‐step activation methodology is capable of generating highly porous AC when compared to two‐step activation route. Cyclic voltammetry analysis showed that for the electrode developed from AC that fabricated via three‐step activation, capacitance retention of 50% is achieved upon tuning the scan rate by 10 times. The same electrode exhibited the capacitance retention of 45% upon increasing the current density by 10 times. We have also compared the electrochemical performance of symmetric and asymmetric supercapacitors. Electrochemical capacitance retention of symmetric and asymmetric supercapacitors is determined to be 100% and 92% respectively after 1000 cycles at the current density of 1 A g−1. Based on the Ragone plot study, it is observed that the maximum energy density of 5 W h kg−1 and the maximum power density of 943 W kg−1 are attained for the case of symmetric supercapacitors. Asymmetric supercapacitor displayed improved energy density of 7.15 W h kg−1 and modest power density of 432 W kg−1.

Investigation on release and migration characteristics of sodium during the combustion of high-sodium coal with phosphorite

To mitigate slagging, fouling, and corrosion from burning high-sodium coal, phosphorite was introduced during combustion. The migration and release characteristics of Na were analyzed at different temperatures and phosphorite ratios. Results show that Na in Shaerhu coal mainly exists in water-soluble (68.75 %) and insoluble forms (22.35 %). As the temperature increases from 700 °C to 1100°C, the water-soluble sodium in the coal ash decreases by 1151 μg∙g−1, and the insoluble sodium increases by 98 μg∙g−1. Phosphorite can react with water-soluble sodium at high temperatures. Adding 15 % phosphorite at 900°C will reduce the water-soluble sodium content by 455 μg∙g−1, increase the insoluble sodium content by 1408 μg∙g−1, and reduce the sodium release ratio by 12.99 %. The softening temperature of Shaerhu coal is 1158°C. After adding phosphorite, the softening temperature of coal ash can be increased to more than 1200°C. Compared with SiO2 used in traditional processes, phosphorite as an additive can improve anti-scaling performance and facilitate ash discharge in solid form. Meanwhile, recycling phosphorite co-combustion with coal for using in thermal phosphoric acid process can increase the conversion ratio of phosphorite by 10 %–20 %.

Sustainable Enhancement of Biogas Production from a Cold-Region Municipal Wastewater Anaerobic Digestion Process Using Optimized Sludge-derived and Commercial Biochar Additives

Anaerobic digestion (AD) of municipal wastewater sludges produces valuable solid digestate and biogas. Biogas is a source of clean energy and enhancement of its production has been of recent interest for increased electricity generation, among other products. The objective of this study was the development of a novel municipal sludge-derived biochar and its application in a municipal wastewater AD system to increase the biogas production rate. Thickened waste-activated sludge (TWAS) samples were collected from the cold-region municipal wastewater treatment plant and used to synthesize biochar applied in the simulation of AD processes using laboratory-scale reactors. The TWAS-derived biochar was synthesized using the commonly used furnace pyrolysis (sludge-based biochar, SBC), and more novel microwave pyrolysis including phosphoric acid as a microwave activator (activated sludge-based biochar, ASBC). The microwave pyrolysis conditions were optimized using a computational fluid dynamics (CFD) technique. In addition, various commercially available carbon-based additives were assessed for their impacts on the AD process including activated carbon, wood-derived biochar, and forest residue-derived biochar. Results showed that the ASBC increased the cumulative methane production by 50% (333 mL/g VS) versus the control sample (221 mL/g VS) after 30 d. The ASBC showed higher surface area, electrical conductivity, and metal contents versus the other biochars which boosted the AD microbial community growth leading to higher organic matter conversion into biogas. In the ASBC-amended digesters, the bacterial phylum Bacteroidota, which contains a major genus of the dgA-11-gut-group, exhibited a synergy between organic substrate fermentation and volatile fatty acid production, resulting in enhanced biogas production. The TWAS biochar demonstrated promising performance in enhancing the AD process fostering energy and resource self-sufficiency at municipal wastewater treatment plants. This smart sludge management aligns well with sustainable waste management practices and clean energy production strategies, especially considering that the biochar was sourced from a readily available continuous waste-product stream.

A rapid and efficient approach for quantifying metformin in human plasma using Ultra-High performance liquid chromatography with UV-Detection: Relevance in Non-Diabetes clinical studies

Metformin, a first-line drug to treat type-2 diabetes, has gained attention in various non-diabetes studies, such as anti-aging, reduced cancer incidence and mortality, and reduced symptomatic viral infection due to its immunomodulatory properties. This study aims to develop and validate a simple and cost-effective ultra-high-performance liquid chromatography method with UV detection (uHPLC-UV) for quantifying metformin in human plasma amidst operational challenges and restricted accessibility to mass spectrometry. Plasma samples were protein precipitated with acetonitrile, and metformin was separated from endogenous plasma components using a Waters Acquity UPLC BEH Amide column, 1.8 µm, (2.1 x 100 mm) with gradient elution using 0.1 M potassium phosphate adjusted with phosphoric acid to pH 5.8, and acetonitrile as mobile phases and detected at 240 nm. Method validation was performed according to U.S. FDA guidelines. Total run time achieved was 3 min and linearity was demonstrated over the range of 0.1–40 mg/L based on linear regression using 1/x weighting. The lowest quantitation limit of 0.1 mg/L was achieved. Excellent recoveries (90.3–98.4 %) and negligible matrix factors (94.6–108.1 %) were observed in the sample preparation, negating the need for using any internal standard. Finally, the developed assay was utilised to measure metformin plasma levels from healthy volunteers recruited in a randomised, double-blind, placebo-controlled study investigating potential immunomodulatory effects of metformin influence on yellow fever viremia.

Enhancing wet phosphoric acid production efficiency with vanadium catalyst waste derived silica

Enhancing wet phosphoric acid production efficiency with vanadium catalyst waste derived silica

Heat capacities and thermodynamic properties of urea phosphate and its aqueous solutions at various temperatures

Urea phosphate was produced through a complexation reaction of phosphoric acid and urea and subsequent cooling crystallization. The elemental composition analysis, XRD, and FTIR all confirmed that the prepared urea phosphate had high purity and good crystallinity, which showed a clear onset melting temperature of 118.12℃ and corresponding enthalpy change of 222.10 J∙g−1 in TG/DSC measurement. Meanwhile, the heat capacities of urea phosphate and its aqueous solution were carefully measured using microcalorimetry with an expanded relative uncertainty better than 2 %. The experimental results revealed that the heat capacity of urea phosphate rises rapidly with temperature, with an increase of 41 % from −20 to 100℃. The experimental heat capacity data were correlated with semi-empirical models of Maier-Kelley equation, Khodakovsky equation and Debye-Einstein equation which all give excellent reproduction of the measured data with very close average deviation around 0.5 %. The enthalpy, entropy, and Gibbs free energy of solid urea phosphate were estimated at various temperatures by integrating heat capacity against temperature with Maier-Kelley equation and the results confirmed urea phosphate is thermally quite stable below 100℃. The heat capacity of urea phosphate aqueous solution increases with concentration and temperature, and there is a strong linear relationship between the solution’s heat capacity and temperature while the composition remains constant. The apparent molar heat capacity of urea phosphate in solution is positive and increases with concentration and temperature. The extrapolated partial molal heat capacity of urea phosphate is temperature independent and shows an average value of −709.4J·K−1·mol−1. Due to the partial dissociation and partial ionization of urea phosphate in solution, the excess molar heat capacities show positive deviation from that of ideal solution, which also increases with the increase of concentration and temperature.

Simultaneous quantitative analysis of some main components in cinnamon leaves (Cinnamomum cassia) by HPLC-PDA

Cinnamon leaves, a part of the cinnamon tree, are used as raw materials to extract cinnamon essential oil and as a spice in food processing. Trans-cinnamaldehyde is the main ingredients that have biological effects and high concentration in cinnamon, cinnamic acid is often used as a marker in the quantification methods of cinnamon, coumarin is the ingredient that needs to be controlled due to risk of liver toxicity. So that, cinnamaldehyde (CAL), cinnamic acid (CA) and coumarin (CM) have been choosen to determin quality of cinnamon leaves. The analytes in the test sample were extracted with methanol:water ratio 9:1 by ultrasound twice 30 minutes and resting for 30 minutes between extractions. The ultrasonic extract was analyzed using an HPLC-PDA, C18 column (250×4.6 mm, 5 µm) at 25°C, mobile phase system consisting of acetonitrile and 0.05% phosphoric acid is eluted according to the program's gradient, detection wavelength 280 nm. The method was determined according to AOAC 2016 guidelines with appropriate specificity and linearity ranging from 51.90-691.31 µg/mL for coumarin, 1.00-20.10 µg/mL for cinnamic acid and 52.45-609.8 µg/mL for trans-cinnamaldehyde, good repeatability with RSD from 0.46% to 0.61%, accuracy of coumarin, cinnamic acid and cinnamaldehyd were 101.0%, 100.7% and 100.7% respectively, meets AOAC requirements at 3 concentration levels. The study applied quantitative research methods to quantify coumarin, cinnamic acid and transcinnamaldehyde on 17 C. cassia leaves samples collected in provinces in Vietnam. In result, analyte concentrations varied widely between samples, with coumarin ranging from 0.53- 2.47%, cinnamic acid from 0.01-0.08%, and cinnamaldehyde from 0.95-2.56%.

Effect of Phosphoric Acid and Soluble Phosphate on the Properties of Magnesium Oxychloride Cement

This study investigates the effects of phosphoric acid (H3PO4), potassium dihydrogen phosphate (KH2PO4) and sodium dihydrogen phosphate (NaH2PO4) admixtures on the setting time, compressive strength and water resistance of magnesium oxychloride cement (MOC). MOC samples incorporating different admixtures are prepared, and their hydration products and microstructures are studied via X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicate that the addition of H3PO4, KH2PO4 and NaH2PO4 reduces the initial and final setting times and decreases the compressive strength. However, the compressive strength of MOC is higher than 30.00 MPa with the addition of 2.0 wt.% phosphoric acid and its phosphate after 14 days of air curing. The water resistance of modified MOC slurries is significantly improved. The softening coefficient of MOC with 2.0 wt.% H3PO4 is 1.2 after 14 days of water immersion, which is 3.44 times higher than that of the neat MOC. The enhancement in water resistance is attributed to the formation of amorphous gel facilitated by H3PO4, KH2PO4 and NaH2PO4. Furthermore, the improvement in water resistance is manifested as H3PO4 > KH2PO4 > NaH2PO4.

Possibility of processing phosphogypsum to obtain an alkalizing reagent

Relevance. The need to develop a technology for the disposal of solid and liquid industrial waste to obtain organic-inorganic fertilizer. The growth of industrial production is accompanied by an increase in waste. In modern society, considerable attention is paid to the problem of processing man-made waste to obtain demanded products. Phosphogypsum is the main by-product of the production of fertilizers and phosphoric acid, it is a multi-tonnage waste, its storage leads to the withdrawal of vast territories from circulation. Liquid waste from pig farms also needs to be processed into organic fertilizers. Aim. To study the process of heat treatment of phosphogypsum in the presence of a reducing agent to obtain an alkalizing reagent. This will make it possible to further organize processing liquid and solid agricultural and industrial waste and produce domestic organic fertilizers Methods. Heat treatment of phosphogypsum in the presence of a reducing agent, followed by the preparation of an aqueous suspension to obtain an agent that reduces the acidity of livestock effluents. The samples of heat-treated phosphogypsum obtained during the study were characterized by X-ray phase analysis, electron microscopy. Suspensions with different pH values were obtained on their basis. Results and conclusions. The authors have studied heat treatment of large-tonnage inorganic waste of the chemical industry – phosphogypsum. It was found that the suspension of phosphogypsum heat-treated in the presence of a reducing agent has increased values of the hydrogen index, which can be used to obtain an alkalizing reagent for treating agricultural waste. The authors revealed the optimal technological modes of obtaining a reagent having the maximum pH value of the suspension: the amount of the introduced reducing agent is 0.16 mol/mol CaSO4, the heat treatment temperature is 1000 °C.

Insight into the chemistry of Folin’s test for uric acid

Folin developed an analytical technique for uric acid spectroscopic determination. It is based on the interaction of uric acid with sodium tungstate in phosphoric acid. This produces an intense blue colour after alkalinization, whose concentration is measured. However, the structure of the organic product obtained was not mentioned. The present communication gives the references related to each reaction step, as well as information about the reaction products obtained in uric acid oxidations carried-out in acidic or in alkaline mediums. The reaction route is as follows: addition of tungstic acid to the C-C double bond, acidolysis of the organo-metallic ester, producing tungstic subacid and an epoxide. Oxirane opening to vicinal diol after reaction with water. Two carbinolamines result, which are broken by protonation at the nitrogen; carbonyl groups are formed at C-4 and C-5 with concomitant elimination of a urea molecule. This way alloxan monohydrate is formed. The blue products obtained are described.

Simultaneous determination of acid carnosic and carnosol in rosemary-containing foods by high-performance liquid chromatography with photodiode array detection (HPLC–PDA)

The research was conducted to develop and validate a simultaneous quantification method for acid carnosic (CA) and carnosol (CAR) in rosemary-containing foods using highperformance liquid chromatography coupled with photodiode array detection (HPLC–PDA), with a simple and fast sample processing procedure. Analytical samples were extracted using a methanol–phosphoric acid mixture (99.5:0.5, v/v) at room temperature for 20 minutes. The chromatographic conditions were as follows: Sunfire C18 column (4.6 mm x 250 mm; 5 µm), mobile phase consisting of 0.1% phosphoric acid – acetonitrile (40:60, v/v), flow rate of 1 mL/min, injection volume of 10 µL, detection at 230 nm. The method was validated according to the Association of Official Analytical Chemists (AOAC) criteria. The results showed that the method had good specificity, and the standard curves of acid carnosic and carnosol were linear in the concentration range of 2.5 – 200 µg/mL. The limits of detection (LOD) for acid carnosic and carnosol were 0.3 µg/mL and 0.25 µg/mL, respectively. The limits of quantification (LOQ) for acid carnosic and carnosol were 1 µg/mL and 0.75 µg/mL, respectively. The recovery rates were in the range of 98.8 – 100.6% (acid carnosic) and 97.5 – 102.2% (carnosol). Repeatability and internal reproducibility met the requirements of AOAC. The method was applied to evaluate the acid carnosic and carnosol levels in 20 food samples collected from the market, such as rosemary leaf powder, dried rosemary leaves, rosemary herbal tea,...

Study on determination of cynarin in dietary supplement containing artichoke by high performance liquid chromatography

There has been no announcement on the standardization and testing of cynarin in dietary supplements containing artichokes in Vietnam. The high-performance liquid chromatography (HPLC) method was developed to determine cynarin in dietary supplements containing artichokes. The sample was extracted twice with 80% methanol solvent and ultrasonicated at 50°C for 20 minutes. Centrifuge at 6000 rpm for 5 minutes, filter, and inject into HPLC system with XBridge C18 column (250 mm x 4,6 mm, 5 µm) and corresponding pre-column, mobile phase consisting of two solvents phosphoric acid 0,1% and acetonitrile eluted according to gradient program, flow rate 1mL/min, detection wavelength 322nm. The calibration curves for cynarin had R2 = 1, and the validation parameters met AOAC standards. The method detection limits and the limit of quantification were 3.00 mg/kg and 10.0 mg/kg, respectively. The validated method was applied to determine cynarin in 15 dietary supplement samples. The content of cynarin varied depending on the manufacturer

Organocatalytic asymmetric cascade bicyclization of 2‐indolylmethanols with α‐(2‐indolyl) propargylic alcohols to access chiral fluorescent hexacyclic bisindoles

A cascade regioselective 1,8‐addition/ biscyclization of 2‐indolylmethanols with α‐(2‐indolyl) propargylic alcohols has been developed via chiral phosphoric acid (CPA) catalysis. A series of chiral cyclopenta[4,5]pyrrolo biindoles bearing a quaternary stereogenic center were obtained in modest to good yields (72‐95%) with high enantioselectivities (82‐94%). Additionally, the photophysical properties of these hexacyclic bisindoles are examined, revealing bright fluorescence with high quantum yields.

Development and validation of RP-HPLC method with UV-DAD detection for simultaneous determination of acesulfame K, sodium saccharin and aspartame in beverages

AbstractArtificial sweeteners are low-calorie substances used as food additives with aim to impart a sweet taste to beverages without adding significant calories. Due to the regulatory compliance regarding the type and the amount of artificial sweetener, and due to the large consumption of beverages and the effects of artificial sweeteners on human health, their identification and quantification is of a great importance. In this research simultaneous determination of acesulfame K (ACE-K), sodium saccharin (Na-SAC) and aspartame (ASP) as the most commonly used sweeteners in beverages was performed with a reversed – phase high performance liquid chromatography (RP – HPLC) with diode array detection (DAD). The best separation of the analytes was achieved on a Poroshell 120 EC-C18 (3.0 × 50 mm, 2.7 µm) column and isocratic elution with a mobile phase consisted of acetonitrile and diluted phosphoric acid (pH = 3.8) with 7/93 volume ratio (V/V), and flow rate of 1 mL min−1. The chromatographic process was followed at 195, 220 and 230 nm, under constant column temperature (25 °C). Under these chromatographic conditions, the total time of analysis was less than 5 min. The developed method was validated for linearity, precision, accuracy, limit of detection (LOD) and limit of quantification (LOQ). The LOD under established chromatographic conditions was 0.03, 0.07 and 0.17 mg L−1 for Na-SAC, ACE-K and ASP, respectively. The amount of artificial sweeteners in analyzed samples ranged from 30.32 to 148.37 mg L−1 for ACE-K, from 16.10 to 93.05 for Na-SAC, and from 6.06 to 512.72 for ASP. The validated method was successfully applied for determination of analytes in different commercially available beverages.

Evaluation of Etching Time Effect on Shear Bond Strength of Orthodontic Brackets Bonded with Self-Adhesive Composite: An in-Vitro Study

Introduction: Precise acid etching of the tooth surface is a significant factor in the strength of the bracket bond. The current study aimed to determine the effect of different application times of acid etching on the shear bond strength of metallic orthodontic brackets under controlled laboratory conditions. Methods: Sixty intact premolar teeth were selected for this in-vitro study. The samples were divided into four groups based on the different acid etching times: 20, 25, 30, and 35 seconds. The teeth surfaces were etched with 37% phosphoric acid according to the specified times, and brackets were bonded to the enamel surface using GC Ortho connect composite. Shear bond strength values of the brackets was measured using a Universal Testing Machine. The amount of Adhesive Remnant Index was also observed using a stereomicroscope. Additionally, the surface roughness of the tooth enamel after bracket bonding was examined using SEM. The results related to shear bond strength were analyzed with one-way ANOVA statistical test and using SPSS version 16 software. The non-parametric Kruskal Wallis (Wallis-Kruskal) test was also used to check the frequency of ARI index. Results: The highest shear bond strength was observed at 25 seconds, and the lowest at 30 seconds. However, there was no significant difference in the shear bond strength of brackets was observed among the four groups (p=0.186). The highest ARI score was observed at 35 seconds, and the lowest at 20 seconds. No statistically significant difference was observed in the ARI scores in different groups. SEM images revealed that the enamel surface porosity was highest at 20 seconds. Conclusion: The results indicate that the shear bond strength and ARI at different acid etching times do not significantly differ. Therefore, orthodontic bracket bonding can be performed with less acid etching time.

Tailored proton conductive membranes of PVdF-co-HFP: Investigating the synergistic effects of ammonium tetrafluoroborate and phosphoric acid dopants on dielectric characteristics

This study investigates the structural, thermal, and dielectric properties of pure PVdF-co-HFP matrix and its composite electrolytes, PVdF-co-HFP/NH4BF4[x], both before and after PA doping, using FTIR, SEM, TGA, and dielectric analyses. FTIR spectra reveal characteristic vibrational bands, confirming the presence of various functional groups and phases. SEM images display a smooth and homogeneous surface morphology for pure PVdF-co-HFP, while the composite electrolytes exhibit irregular dispersion of NH4BF4 salt and rougher surfaces upon PA doping. TGA analysis shows that the onset of thermal degradation occurs at approximately 370 ℃ for pure PVdF-co-HFP, while PA-doped samples demonstrate higher decomposition temperatures, exceeding 400 ℃ due to hydrogen bonding and ionic complex formation. The presence of NH4BF4 and PA doping also affects the crystallinity of the PVdF-co-HFP matrix, notably shifting the transition temperatures of the alpha and beta phases. Ionic conductivity measurements indicate that PA doping significantly enhances conductivity by increasing charge carrier concentration and facilitating ion transport. PA-doped PVdF-co-HFP/NH4BF4[10] showed the highest conductivity reaching 1.68 × 10−3 S.cm−1 at 1 MHz and 400 K. Dielectric studies reveal frequency-dependent behavior, with dielectric constant (ε') and loss (ε") showing distinct trends influenced by salt concentration and PA doping. The dielectric tangent loss (tanδ) of PA-doped PVdF-co-HFP/NH4BF4 composite membranes exhibits frequency and temperature dependence. At higher temperatures, tanδ increases with frequency, showing a resonance peak that shifts towards higher frequencies. The study elucidates the impact of PA doping on the structural, thermal, and electrochemical performance of PVdF-co-HFP/NH4BF4 composites, providing insights for their potential applications in advanced electrolyte systems.