Effects Of Various Acids Research Articles

Effects of various acids on physical stability, rheological characteristics and curcumin encapsulation of whey protein isolate Pickering emulsion gels

Acid treatment can alter the functional properties of whey protein isolate (WPI), but the effect of different acids on properties of WPI‐stabilised Pickering emulsion gel (PE) is unknown. Compared with WPI‐PE, droplet size of the acid‐treated WPI‐PE decreased but its zeta potential, apparent viscosity, binding water capacity and curcumin encapsulation were enhanced. Due to the formation of the tightest gel structure of malic acid‐Pickering emulsion gel, it showed the highest viscoelastic modulus, bound water content and gel stability. This work would introduce a novel method for the development of PEs with good gelatinisation and curcumin delivery system for food processing.

Acid Resistance of Geopolymer Concrete – Literature Review, Knowledge Gaps, and Future Development

Geopolymer concrete, a sustainable and durable alternative to conventional Portland cement-based concrete, has gained significant attention in recent years. Its reduced carbon footprint and superior mechanical properties make it a viable option for various construction applications. However, acid resistance remains a critical area of concern, particularly in environments where exposure to acidic substances is prevalent. This review paper delves into the acid resistance of geopolymer concrete, providing a comprehensive overview of the latest research findings, methodologies, and advancements in the field. The paper commences by exploring the fundamental principles of geopolymer chemistry. Subsequently, the paper meticulously reviews the experimental results of studies investigating the acid resistance of geopolymer concrete. It focuses on the effects of various acids commonly encountered in industrial and environmental settings, such as sulfuric acid, hydrochloric acid, and organic acids. The paper summarizes the key findings from the reviewed literature, highlighting the strengths and limitations of geopolymer concrete in terms of acid resistance. It identifies the factors that contribute to enhanced acid resistance and suggests potential strategies for further improvement. Furthermore, the paper outlines future research directions, emphasizing the need for long-term studies, the development of standardized testing methods, and the exploration of novel geopolymer formulations with superior acid resistance.

Structural and gelling properties of whey proteins influenced by various acids: Experimental and computational approaches

Five different acids, i.e., hydrochloric acid (HCl), acetic acid, lactic acid, γ-aminobutyric acid (GABA) and taurine were applied to investigated their effects on heat-induced gelation properties of whey protein isolate (WPI) at pH = 5.5. All WPI gels were found to have self-similar structures with the fractal dimension, df = 2.40. Those denatured WPI formed strong physical gels that were susceptible to shear and strain. Of all the acids, HCl, GABA and taurine significantly strengthened WPI gels. Moreover, denser packing of protein aggregates was observed from the gels with GABA and taurine. Besides experimental approaches, molecular dynamics (MD) simulations were also applied to investigate the effects of various acids on denaturation of β-lactoglobulin (β-LG). GABA and taurine were found to protect β-LG from denaturation and delayed the molecular heat-induced unfolding. Moreover, presence of HCl, GABA and taurine conserved the rigidity of unfolded β-LG and localized the residue –SH121, which was believed to result in promoted reaction-limited clustering aggregations (RLCA) of β-LG molecules and strengthened WPI gels. Further studies suggested that there was no strong binding or aggregation between cations (Na+) or anions/zwitterions and β-LG molecule. Therefore, the effects from various acids (anions/zwitterions) on β-LG and WPI were supposed to result from long-distanced electrostatic interactions and/or their effects on the protein hydration shells.

Mechanism analysis of hydrochloric and acetic acids dissolving clay minerals

During acidification of the reservoir, the acid concentration will continually decrease as the reaction progresses. If the reaction time is long enough, the acid will eventually be exhausted. According to this phenomenon, the acidification of the reservoir can be regarded as the reaction between different concentrations of acid and minerals. Mineral dissolution is the common method for carbonate reservoirs to reform reservoirs and acid fracturing. In addition to carbonate minerals, carbonate reservoirs are likely to contain clay minerals, but less study has been done on acids with different concentrations and clay minerals. In this work, hydrochloric acid (HCl), acetic acid (HAC), and mixture acid (HCl + HAC) were used to dissolve chlorite, montmorillonite, kaolinite, and illite, respectively. The mechanism of acid dissolving clay minerals was analyzed by XRD, ICP-OES, and SEM. Moreover, we found that a high concentration of HCl has an anti-swelling and shrinkage effect on montmorillonite. The result shows that during the processes of HCl dissolving chlorite, montmorillonite and illite, there is SiO2 precipitate generated even at solutions’ pH of 0.5. In addition, chlorite may generate bischofite precipitate. Moreover, the effect of HCl dissolving chlorite is larger than that of other clay minerals. Also, by comparing the effects of various acids dissolving clay minerals, the effect of HAC dissolving clay minerals is lower than that of HCl, and the precipitate is not formed. The mixture acid dissolving clay minerals is better than that of single acid except for montmorillonite. For reservoirs with high chlorite content, the concentration of HCl can be appropriately reduced and the concentration of HAC can be increased; for reservoirs with high montmorillonite content, the concentration of HCl can be increased. Illite and kaolinite react weakly in HCl and hardly react with HAC.

Determination of Th(IV) in Natural Waters after Preconcentration with a Chelating Sorbent

Chelating sorbents containing norsulfazole and sulfadimezine fragments were prepared by modification of maleic anhydride-styrene copolymer with amines. The conditions of the Th(IV) sorption onto these sorbents were studied. The maximal sorption was observed at pH 5. The effect of various acids on the Th(IV) desorption from the sorbents was examined. The developed procedure was applied to the Th(IV) determination in water via preconcentration.

CONCENTRATION OF THORIUM (IV) BY CHELATING SORBENT

The paper analyses complexation of thorium(IV) with 2,3,4-trihydroxy-4’-fluoroazobenzene. A complex is formed immediately after mixing the components. Their molar ratio (1:2) was established using the methods of Starik–Barbanel relative yield, equilibrium shift and isomolar series. The maximum light absorption of the complex is observed at 440 nm, with the molar absorption coefficient being equal to 1.80×10 4 . In this work, we synthesised a new sorbent containing fragments of para-aminosalicylic acid. Identification of sorbents was carried out using IR spectroscopy. Sorption was studied in static and dynamic modes. The optimal conditions for concentration were investigated. The magnitude of the sorption and the degree of metal extraction was calculated from its residual concentration in the solution using a spectrophotometric method. Our results show that the maximum sorption is observed at pH = 4. In the course of preliminary kinetic experiments, it was found that the maximum sorption of cadmium is attained within 2 hours, remaining practically at the same level thereafter. The effect of the ionic strength of the solution was studied using the photometric method. Thorium(IV) was sorbed from solutions having an ionic strength of 0.1–1.4. It is shown that a significant decrease in the sorption of thorium(IV) occurs in solutions with an ionic strength of more than 0.2 M. The effect of metal concentration on sorption was also investigated. An isotherm of thorium sorption by the synthesised sorbent was constructed. An increased concentration of thorium(IV) in the solution leads to an increase in the amount of sorbed metal, with the maximum concentration being reached at 1856 mg/l. We also studied the effect of various acids (HClО 4 , H2SО 4 , HNО 3 , HCl) on the desorption of thorium(IV) from the sorbent: thorium(IV) was quantitatively desorbed by 2 M nitric acid. The degree of extraction of thorium ions (IV) under optimal conditions exceeds 95%. The study has revealed the possibility of using the matrix of a copolymer of maleic anhydride and styrene modified by para-aminosalicylic acid for sorption-photometric determination of thorium(IV). Following regeneration, this sorbent can be reused.

The Effect of Various Acids to the Gelation Process to the Silica Gel Characteristic Using Organic Silica

Bagasse ash is solid waste of cane sugar industry which contain of silica more than 51%. Some previous study of silica gel from bagasse ash have been conducted often and been applied. This study concerns about the effect of various acid used in the process of gelation to the characteristic of silica gel produced. Then, this silica gel will be used as adsorbent. As that, the silica gel must fulfill the requirements of adsorbent, as have good pores characteristics, fit in mesoporous size so that adsorbent diffusion process is not disturbed. A fitted pores size of silica gel can be prepared by managing acid concentration used. The effect of acid, organic acid (tartaric acid) and inorganic acid (hydrochloric acid), is investigated in detail. The acid is added into sodium silicate solution in that the gel is formed, the pores structures can be investigated with BET, the crystal form is analyzed with XRD and the pore structure is analyzed visually with SEM. By managing the acid concentration added, it gets the effect of acid to the pore structure of silica gel. The bigger concentration is, the bigger the pore’s size of silica gel produced.

Catalytic Effects of Various Acids on Microwave-assisted Depolymerization of Organosolv Lignin

The catalytic effects of various acids (sulfuric acid, hydrochloric acid, phosphoric acid, and formic acid) on the depolymerization of organosolv lignin under mild microwave heating (approximately 100 W, 160 °C for 30 min) were investigated. The liquid product was separated from the solid residue and analyzed by gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FTIR). The solid residue was analyzed with thermogravimetric analysis (TG-DTG) and observed by scanning electron microscopy (SEM). The experimental results showed that sulfuric acid exhibited a better catalytic effect than the other acids. The SEM and TG-DTG results showed that the solid residue from sulfuric acid-catalyzed depolymerization was not only remarkably smaller than that of the other groups, but also presented a faster thermal decomposition rate. The molecular weight (Mw, weight-average) of the liquid product (Mw = 1020) from sulfuric acid-catalyzed depolymerization was also lower than that of the other groups.

Effect of various acids on physicochemical and functional characteristics of gelatin from swim bladder of rohu (Labeo rohita).

Influence of various acids (acetic acid, phosphoric acid, and propionic acid) at different concentrations (0.05, 0.1, and 0.2M) on the extraction yield, physicochemical and functional properties of gelatin from Labeo rohita swim bladder were investigated. Highest gelatin yield (44.22%, dry weight basis) was obtained in a sample prepared by without acid pretreatment (GWA) of swim bladder as compared to acid pretreatment counterparts. Amongst the acid pretreatments, propionic acid (GPrA) showed the highest gelatin yield, followed by acetic acid (GAA) and phosphoric acid (GPA) at all concentrations used, respectively. Moreover, with increased concentrations of all acids, the decrease in gelatin yield was observed for all the acids. GWA showed higher protein and hydroxyproline content than that of acid counterparts (P<0.05). Amino acid analysis of gelatins showed glycine as the major amino acid in all gelatins followed by proline, glutamic acid and alanine, respectively. GWA showed α (α1 and α2) and β-chains as the predominant components with low molecular weight peptides. However, GPrA, GAA, and GPA had α1 and α2 dominant constituents. FTIR spectra of gelatins revealed that the loss of the triple-helix was found in GPA, GAA, and GPrA, compared to GWA. Among gelatin samples, GWA showed the highest solubility at all pH tested followed by GPrA, GPA, and GAA respectively. Furthermore, GWA exhibited higher emulsifying, foaming and gelling properties as compared to GPrA, GPA, and GAA, respectively. Therefore, the acid pretreatment of swim bladder had a negative impact on the extraction yield, physicochemical and functional properties of gelatin from rohu swim bladder.

The Effect of Various Acids on Properties of Microcrystalline Cellulose (MCC) Extracted from Rice Husk (RH)

Microcrystalline cellulose (MCC) was successfully extracted from rice husk (RH) via acid hydrolysis process using nitric acid (HNO3) in comparison with sulphuric acid (H2SO4) and hydrochloric acid (HCl). MCC-RH extracted using HNO3 produced the highest percentage yield at 83.5% as compared to H2SO4 and HCl at 80.6% and 81.8% respectively. Analysis of Fourier Transform Infrared (FTIR) spectroscopy affirmed the successive elimination of non-cellulosic material from RH cellulose resulting highly purified MCC-RH. X-ray Diffraction (XRD) analysis showed MCC-RH treated with HCl gives the highest crystallinity index value of 54.2% while HNO3 and H2SO4 produced comparable results of 52.4% and 49.7% respectively. The results indicate successive extraction of MCC-RH using HNO3 that has great potential to replace strong acid such as H2SO4 and HCl in acid hydrolysis.

A comparison of acidic and enzymatic hydrolysis of rutin

Rutin and its hydrolysis products (isoquercitrin and quercetin) are widely used as important materials in food and pharmaceutical industry. In this study, the effects of various acids and enzymes as catalysts on the hydrolysis reaction of rutin were studied. In comparison with acidic and enzymatic catalysis of rutin, the research results indicated that there was a sharp difference in the selectivity of hydrolysis product between the methods. When 2.5% H3PO4, 1% HCl and 0.5% H2SO4 were used as catalysts, transformation yields of isoquercitin hydrolyzed from rutin were 9.60, 0.69 and 1.25%, but those of quercetin were 11.13, 100 and 2.57%, respectively. When hesperidinase, snailase and cellulase-T2440 were used as catalysts, transformation yields of isoquercitin hydrolyzed from rutin were 43.21, 3.07 and 0.00%, but those of quercetin were 58.10, 96.39 and 30.89%, respectively. In conclusion, the aglycon of rutin was deglycosolated easily under mild acidic hydrolysis conditions at appropriate temperatures, but its secondary glucoside was difficult to be obtained. Contrarily, the prepared isoquercitrin by enzymatic hydrolysis of rutin was preferable to the acidic hydrolysis, especially for hesperidinase.

ChemInform Abstract: An Unprecedented, Tandem Aldol-Grob Reaction Sequence.

The authors report an unprecedented, tandem Aldol-Grob sequence involving the reaction of ketones with aromatic aldehydes in nonnucleophilic solvents in the presence of boron trifluoride. Although a detailed study of the reaction mechanism has not yet been completed, the consistent formation of (E)-alkene products, as well as the fact that aromatic aldehydes appear to be required, would point toward the intermediacy of a carbocation derivative. A reasonable mechanism would involve the formation of the mixed aldol followed by the formation and subsequent nonsynchronous ring opening of a lactol. The proposed fragmentation is reminiscent of two-step Grob fragmentations that have been reported for N-halo-{alpha}-amino acids and cyclobutane hemiacetals as well as the acid-catalyzed fragmentation of {beta}-hydroxy acetals. The authors examined the effect of various acids on the reaction sequence in order to ascertain which would be most efficient. They conclude that boron trifluoride is the most effective of the acids studied in achieving the new tandem condensation-cleavage sequence.

Loss of Bonded Phase in Reversed-Phase Liquid Chromatography in Acidic Eluents and Practical Ways To Improve Column Stability

Silica-based, reversed-phase liquid chromatographic (RPLC) stationary phases are very widely used to separate basic compounds in acidic eluents due to their high efficiency, good mechanical strength, and the versatile selectivity offered by different functional groups and the chemistry on the silica surface. However, the stability in acid of most silica-based stationary phases is poor, especially at elevated temperatures, due to hydrolysis of the siloxane bonds, which hold silanes on the silica substrate. This hydrolysis is commonly believed to be solely the result of catalysis by protons. However, we show that various metal cations (principally Fe3+/Fe2+, Ni2+, and Cr3+) released from acid corrosion of the stainless steel inlet frit greatly accelerate the hydrolysis of the siloxane bond. Furthermore, these metal cations, and not the high acidity per se, are mainly responsible for column instability. We show that removing the stainless steel inlet frit, or use of a titanium frit, greatly reduces or totally eliminates corrosion of the inlet frit and radically improves retention stability. The effects of various acids and types of organic modifier were also studied. These observations suggest a number of practical approaches that can significantly extend the lifetime of any RPLC stationary phase in acidic media at elevated temperature.

Production of trehalase inhibitor validoxylamine A using acid-catalyzed hydrolysis of validamycin A

As a competitive trehalase inhibitor and lead compound with broad uses, validoxylamine A has been increasingly studied for its many possible applications. The process of acid-catalyzed hydrolysis of validamycin A was investigated for production of validoxylamine A. The effects of various acids and substrate concentrations were explored, and the mechanism of acid-catalyzed hydrolysis of validamycin A was proposed. Results demonstrated that the optimal condition of acid hydrolysis of validamycin A included 1 M H 2SO 4 and a 30% (w/v) initial validamycin A concentration in a 1 h reaction time.

Mechanical Properties and Swelling Behavior of Short Glass Fiber Reinforced Polyester Composites

Chopped strand glass fiber reinforced particle-filled polymer composite with different volume fractions of glass fibers has been investigated for tensile strength. Both the properties have been studied with respect to varying fiber content i.e., from 1 to 10%. In addition, the effect of various acids, alkalies, and solvents has been investigated. It has been found that fiber reinforcement increases the chemical absorption. Swelling studies have also been done for NaCl (15%) and distilled water, and the diffusivity coefficient and sorption coefficient are calculated. The sorption coefficient increases with increasing fiber content while the diffusivity coefficient decreases with increasing fiber content.

Augmenting effect of acetic acid for acidification on bactericidal activity of hypochlorite solution.

Bactericidal activity of chlorine solution is enhanced by weak acidification. We compared the effects of various acids on the bactericidal activity of hypochlorite solution to establish a method for safe and effective use of an acidic hypochlorite solution. The bactericidal activities of acidic hypochlorite solutions that had been adjusted to pH 5.0 with hydrochloric acid, acetic acid, citric acid, lactic acid, formic acid, phosphoric acid or sulphuric acid against Bacillus subtilis spores were compared. The acidic solutions prepared with hydrochloric acid and acetic acid showed the highest bactericidal activity, and all of the spores (5 x 106 cfu ml(-1)) were killed within 10 min. On the other hand, the solutions prepared with citric acid and lactic acid showed no bactericidal activity against any bacterial strains tested in this study despite the low pH. The amount of chlorine gas produced by the preparation using acetic acid was sixfold less than that produced from the preparation using hydrochloric acid. Acetic acid is the most suitable and safe acid for the preparation of an acidic hypochlorite solution. The results of this study provide useful information for establishing a method for safe and effective use of an acidic hypochlorite solution.

Effect of various acids at different concentrations on the pinacol rearrangement

The formation of side products in the pinacol–pinacolone rearrangement was studied as a function of concentration and strength of various aqueous acids using 1H NMR spectroscopy. In all cases, pinacolone was the principal product and in most cases, its relative yield decreased with respect to 2,3-dimethyl-1,3-butadiene, when the acid concentration was lowered or the corresponding conjugate base was added.

Effect of Various Acids and Sulfites in Steep Solution on Yields and Composition of Corn Fiber and Corn Fiber Oil

ABSTRACTThe addition of six acids (organic and inorganic) and four sulfite compounds (including gaseous SO2) during the conventional corn wet‐milling steeping process of two yellow dent corn hybrids were evaluated for the effect on corn fiber yield, corn fiber oil yield, and the composition of three phytosterol compounds (ferulate phytosterol esters [FPE], free phytosterols [St], and phytosterol fatty acyl esters [St:E]) in the corn fiber oil. No significant effect of different sulfite compounds and acids were observed on corn fiber yields. However, a significant effect was observed on corn fiber oil yield and the composition of corn fiber oil for phytosterol compounds. Three of the sulfite compounds (including gaseous SO2) caused very little effect on the levels of phytosterol compounds compared with the control sample (corn steeped with sodium metabisulfite and lactic acid). However, for one hybrid, ammonium sulfite gave a significantly higher yield of FPE and St:E and had no effect on the yield of St. For the other hybrid, it gave a significantly higher yield of FPE and had no effect on the yield of St and St:E compared with the control sample. This indicates that the effect of these sulfite compounds on yields of these phytosterol compounds in corn fiber oil is probably hybrid‐dependent. No significant effect of acids was observed on corn fiber yields, but significant effects were observed on corn fiber oil yields and yields of phytosterol compounds in the corn fiber oil. The effect also seems to be hybrid‐dependent because different acids affected the two hybrids differently. Overall, it seems that weak acids have a positive effect on increasing the individual phytosterol compounds in the corn fiber. When comparing the effect of experimental acids and sulfites on the two hybrids, acids have a more positive effect than sulfites in increasing the yield of phytosterol compounds in corn fiber oil.

Preparation of molecular-sieving glass hollow fiber membranes based on phase separation

Glass hollow fiber membranes with ultra-micropores (pore diameter less than 1 nm) were prepared by acid leaching. The effects of various acids and leaching times on the preparation of the membranes were investigated. It was found from acid leaching that the sodium ions of the Al-0 (composition: 62.5SiO 2–28.3B 2O 3–9.2Na 2O wt.%) and Al-3 (composition: 62.5SiO 2–27.3B 2O 3–7.2Na 2O–3.0Al 2O 3 wt.%) glass hollow fibers were completely eluted after 10 and 90 min, respectively, with 3 mol/dm 3 HNO 3, and after 30 and 90 min, respectively, with 3 mol/dm 3 H 3PO 4 or 3 mol/dm 3 CH 3COOH. Ideal separation factors of H 2/N 2 were measured at 373 K using a gas mixture of 50% H 2–50% N 2. The membranes showed highly selective separation of hydrogen. Values for the Al-0 hollow fiber membrane treated with 3 mol/dm 3 HNO 3 reached more than 80. However, ideal separation factors of H 2/N 2 for the Al-3 hollow fiber membranes treated with various acids were smaller. This is thought to be due to the addition of Al 2O 3. Four coordination aluminum species (AlO 4 −) are strongly attracted to alkali metal ions because of charge compensation. Sodium ions in the Al-3 glass hollow fibers were, therefore, prevented from moving within the glass network and the destruction of the glass network during acid leaching caused defects in the Al-3 glass hollow fiber membranes. The formation mechanism of the ultra-micropores was also investigated. From N 2 adsorption measurement and gas separation measurement, it was concluded that the ultra-micropores of the membranes were formed by elution of the phase-separated sodium borate-rich phase at sub-nanometer level and that these defect-free membranes could only be obtained by using phase separation rather than elution of homogeneously distributed ions from homogeneous glasses (no phase separation) such as the alkali–silicate glasses reported previously.

Improved Separation and Determination of Rare Earth Metal Ions in Real Samples by Capillary Electrophoresis with Indirect UV Detection

The separation of rare earth metal ions by capillary electrophoresis in the presence of imidazole as the UV-absorbing background electrolyte, and lactic acid or α-hydroxyisobutyric acid (α-HIBA) as the complexing agent, with indirect UV absorbance detection was investigated. The effects of various acids in the running buffer, pH of buffer and the concentration of complexing agent on the separation were examined. It was observed that the acid used for adjusting the pH of the buffer was another important factor, besides the concentration of the complexing agent that affects the separation of rare earth metal ions. The results showed that under a positive voltage of 10.0 kV, fourteen rare earth metal ions could be baseline separated within 9 minutes using 0.02 mol/1 imidazole containing 8x10−3 mol/1 α-HIBA at pH 3.4 adjusted with hydrochloric acid. The detection limits of La, Ce, Pr, Nd, Sm and Tb were 5x10−6 mol/1. The contents of La, Ce, Pr, Nd and Sm in real samples from Gansu Rare Earth Company were determined quantitatively using Tb (III) as an internal standard. The results were consistent with those of ICP.