Chain Length Of Carboxylic Acid Research Articles

Mesoporous silica-grafted deep eutectic solvent-based mixed matrix membranes for wastewater treatment: Synthesis and emerging pollutant removal performance

Abstract Nano-enhanced membrane technology and deep eutectic solvents (DESs) have demonstrated effectiveness in addressing emerging environmental pollutants. This research centers on purifying water by removing heavy metals employing membranes enhanced with mesoporous silica and DES. Various DESs, including hexanoic acid, octanoic acid, and decanoic acid, were synthesized using tetrabutylammonium bromide (TBABr) as a base. The study combined a polysulfone-based membrane with mesoporous silica, aiming for efficient indigenous crafting to remove heavy metals. Mesoporous silica was blended with the synthesized DES solution, creating diverse membranes for heavy metal separation. The study characterized these membranes using various techniques such as scanning electron microscopy, atomic force microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and contact angle measurements. Surface mapping confirmed the integration of silicon-based DES, reducing the membrane surface roughness from 4 to 1.4 nm. By adjusting the carboxylic acid chain length with TBABr and adding mesoporous silica, leaching ratios were reduced from 4.2 to 2.3%. Silica-grafted DES-based membranes exhibited a progressive increase in flux from 2.6 to 26.67 L/m2 h. The synthesized silicon-based membranes demonstrated outstanding performance, achieving rejection rates exceeding 80% for chromium and arsenic, maintaining an impressive 90% flux recovery ratio even at high flux rates. This study will envision the potential of nano-enhanced membrane technology utilizing DES for sustainable water purification and wastewater treatment applications to achieve the sustainable development goal (SDG) of clean water and sanitation (SDG-6).

The role of hydrochloric acid pretreated activated carbon in chain elongation of D-lactate to caproate: Adsorption and facilitation

Medium chain fatty acids (MCFA) generation is attracting growing interest due to fossil fuel depletion. To promote the production of MCFA, especially caproate, hydrochloric acid pretreated activated carbon (AC) was introduced into chain elongation fermentation. In this study, the role of pretreated AC on caproate production was investigated using lactate and butyrate as electron donor and electron acceptor, respectively. The results showed that AC did not improve the chain elongation reaction at beginning but promoted the caproate production at later stage. The addition of 15 g/L AC facilitated reactor reaching the peak of caproate concentration (78.92 mM), caproate electron efficiency (63.13%), and butyrate utilization rate (51.88%). The adsorption experiment revealed a positive correlation between the adsorption capacity of pretreated AC and the concentration as well as the carbon chain length of carboxylic acids. Moreover, the adsorption of undissociated caproate by pretreated AC contributed to a mitigated toxicity towards microorganisms, thereby facilitating the production of MCFA. Microbial community analysis revealed an increasing enrichment of key functional chain elongation bacteria, including Eubacterium, Megasphaera, Caproiciproducens, and Pseudoramibacter, but a suppression on acrylate pathway microorganism Veillonella, as the dosage of pretreated AC increasing. The findings of this study demonstrated the substantial impact of the adsorption effect of acid-pretreated AC on promoting caproate production, which would aid to the development of more efficient caproate production process.

Effects of acidity, number of hydroxyl group, and carbon chain length of carboxylic acids on starch cross-linking

Corn starch film samples cross-linked using malic, malonic, and succinic acids, and thermoplastic starch were characterized and tested for their water absorption, surface morphology, structural change, and thermomechanical properties. The acids vary in acidity, number of hydroxyl groups, and carbon chain length. The presence of an additional hydroxyl group has helped malic acid form more hydrogen bonding between starch molecules. The relatively higher acidity in malic acid compared to succinic acid is found to be another factor for its better cross-linking potential. The additional carbon chain in succinic acid, which reduces its solubility and acidity; has negatively affected its cross-linking potential. Among the three variables studied, number of hydroxyl group has highly influenced the cross-linking potential, followed by acidity and carbon chain length, respectively. Consequently, the elongation at break and water absorption resistance of thermoplastic starch were improved from 108.63 ​MPa to 175.72 ​MPa and from 140% to 80%, respectively, cross-linking corn starch with malic acid.

The Effect of Acidity, Number of Hydroxyl Group, and Carbon Chain Length of Carboxylic Acids on Starch Cross-Linking

The Effect of Acidity, Number of Hydroxyl Group, and Carbon Chain Length of Carboxylic Acids on Starch Cross-Linking

Conversion of C2–4 Carboxylic Acids to Hydrocarbons on HZSM-5: Effect of Carbon Chain Length

The conversion of C2–4 carboxylic (acetic, propionic, and n-butyric) acids on HZSM-5 was studied at 350 °C. The reaction proceeds through ketonization (to acetone, 3-pentanone, and 4-heptanone, respectively), aldol condensation, and tertiary reactions to aromatics-rich hydrocarbons. The product distribution is influenced by the carbon chain length of carboxylic acids due to the shape selectivity of ZSM-5. The turnover frequency (TOF) of ketonization of carboxylic acids decreases while the TOF of aldol condensation of corresponding ketones increases with increasing carbon chain length. Langmuir–Hinshelwood mechanism analysis shows that the true activation enthalpy of both ketonization and aldol condensation increases with increasing carbon chain length, due to the increased steric hindrance for the formation of a C–C bond. However, the true Gibbs free activation energy increases for ketonization but decreases for aldol condensation with increasing chain length, due to a greater contribution of activation e...

Preparation of silver-exchanged heteropolyacid catalyst and its application for biodiesel production

ABSTRACT In this study, the silver-exchanged heteropolyacids were prepared by a simple and environmentally friendly ion exchange method, were found to be active in the esterification of oleic acid with methanol to produce biodiesel. The catalysts were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and scanning electron microscopy (SEM), separately. The effect of various factors was investigated to optimize the reaction conditions. The results showed that the oleic acid conversion can reach 91.3% after reacting for 3 h at 70°C, with oleic acid to methanol ratio of 1:10 and the amount of catalyst of 5 wt.%. Moreover, the catalyst could be easily separated from the reaction mixture and used repeatedly for five cycles with the oleic acid conversion over 50.1%, due to its relative stability. In particular, this catalyst can also catalyze other esterification of fatty acids with different chain length of carboxylic acid and high acid value non-edible oils, which may provide significant benefits for developing an environmentally benign and continuous process for synthesizing biodiesel in the future.

Friction Mechanisms by Carboxylic Acids in Aqueous Lubricants

Carboxylic acids are well known for their friction-reducing abilities driven by the formation of low-shear-strength films on the steel surface. However, understanding of the adsorption mechanisms especially in polar solvents is yet not well explored. In this work, atomic force microscopy was used to visualise the adsorption behaviour of various carboxylic acids in both polar and less-polar solvents. The work was continued with a tribological study of the lubricants additivated with carboxylic acids in a laboratory scale ball-on-disc tribometer. During this study, the effect of concentration and carboxylic acid chain length was studied in polar media (water-based lubricants) and compared with commonly used synthetic non-polar lubricant (poly-α-olefin, PAO). It was observed that for both polar and less-polar lubricants, surface coverage of carboxylic acids increased with increasing length of hydrocarbon tail. In less-polar lubricants, carboxylic acids adsorbed to the surface by spreading on it evenly, whereas in polar lubricants, very dense multi-layered formation was promoted. Friction reduction achieved with the use of carboxylic acids in the non-polar lubricant was not as efficient as in the case of the polar lubricant. This was associated with the more pronounced multilayer formation of carboxylic acids in the polar lubricants, facilitating higher friction reduction as compared to the adsorption of carboxylic acids in a dense monolayer form seen in the less-polar lubricant.

Laser synthesized TiO2-based nanoparticles and their efficiency in the photocatalytic degradation of linear carboxylic acids

Titanium dioxide nanoparticles were synthesized by laser pyrolysis, their surface and electronic properties were modified by gold and/or nitrogen. These materials were characterized by different techniques like X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). Time resolved conductivity (TRMC) was used to study the charge separation of electron/hole pairs. Altogether (XPS, EPR, TRMC), the physicochemical characterizations are well correlated with chemical photoactivity of the different samples. Their photocatalytic activity was evaluated for the degradation of linear carboxylic acids (C2-C3) under UV and visible illumination. The decomposition rate of acids was measured, it shows that the modification with gold increases the photoactivity while the presence of nitrogen slows down the process. Such observations are in good agreement with evolution of TRMC signals. A degradation pathway has been determined by identification of intermediate products by chromatography and EPR, results show different intermediate species. In particular EPR confirms the presence of NO2− paramagnetic centers and shows two novel N centered paramagnetic centers. A decrease of the degradation rate is observed with increase of carboxylic acid chain length.

Impact of Macroporosity on Catalytic Upgrading of Fast Pyrolysis Bio-Oil by Esterification over Silica Sulfonic Acids.

Fast pyrolysis bio‐oils possess unfavorable physicochemical properties and poor stability, in large part, owing to the presence of carboxylic acids, which hinders their use as biofuels. Catalytic esterification offers an atom‐ and energy‐efficient route to upgrade pyrolysis bio‐oils. Propyl sulfonic acid (PrSO3H) silicas are active for carboxylic acid esterification but suffer mass‐transport limitations for bulky substrates. The incorporation of macropores (200 nm) enhances the activity of mesoporous SBA‐15 architectures (post‐functionalized by hydrothermal saline‐promoted grafting) for the esterification of linear carboxylic acids, with the magnitude of the turnover frequency (TOF) enhancement increasing with carboxylic acid chain length from 5 % (C3) to 110 % (C12). Macroporous–mesoporous PrSO3H/SBA‐15 also provides a two‐fold TOF enhancement over its mesoporous analogue for the esterification of a real, thermal fast‐pyrolysis bio‐oil derived from woodchips. The total acid number was reduced by 57 %, as determined by GC×GC–time‐of‐flight mass spectrometry (GC×GC–ToFMS), which indicated ester and ether formation accompanying the loss of acid, phenolic, aldehyde, and ketone components.

Thermal and mechanical properties of tailor-made unbranched α-1,3-glucan esters with various carboxylic acid chain length

The convenient and environmentally friendly method for in vitro polymerization catalyzed by glucosyltransferase, designated as GtfJ, extracted from recombinant E. Coli was used to synthesize tailor-made α-1,3-glucan (α-1,3-d-glucan) having moderate molecular weight (Mw=2.0×105) and no branches. With the aim to improve thermoplasticity of this polysaccharide, after in vitro synthesis, chemical modification by acylation was selected and then fully substituted α-1,3-glucan esters were successfully obtained via both homogeneous and heterogeneous methods. Thermal degradation temperature of α-1,3-glucan esters was improved after esterification and dependent on neither side chain length nor synthesis methods. DSC curves suggested a presence of crystal structure in α-1,3-glucan acetate, propionate, butyrate, valerate and hexanoate due to detectable melting endotherm, whereas octanoate exhibited amorphous behavior. Tm’s of α-1,3-glucan esters were relatively high, more than 200°C, in comparison with commercial plastics. The shorter chain length of acid component, the higher Tm and Tg ester products exhibited. In addition, tensile strength of α-1,3-glucan esters decreased in contrast with elongation at break with an increase in alkyl chain length of an acid component. Thus, crystalline and amorphous α-1,3-glucan esters with adjustable thermal and mechanical properties obtained from this research are promising materials for continuing applied researches and contemplating the future application in bio-based thermoplastic materials.

Thermodynamic study of interactions in binary liquid mixtures of 2-Chloroaniline with some carboxylic acids

ABSTRACTDensities, speed of sound and dynamic viscosity of liquid mixtures of 2-Chloroaniline with carboxylic acids (ethanoic acid, propanoic acid and butanoic acid) have been calculated over the entire composition range and at T = (303.15–318.15) K. Changes in the physical properties have been studied as a function of temperature and alkyl chain length of carboxylic acids. By using density, speed of sound, viscosity data the excess molar volume (), excess isentropic compressibility (), excess Gibbs energy of activation flow () of liquid mixtures have been calculated. In addition, excess partial molar volume, , excess partial isentropic compressibility, , and excess partial molar volume, , excess partial isentropic compressibility, , at infinite dilution over the whole composition range have also been calculated. Further the topology of electron density obtained by non-covalent interaction plots are used to identify the evolution of strong and weak interactions between dimers of binary liquid mixtures.

Fast, High Yield, and High Solid Loading Synthesis of Metal Selenide Nanocrystals

The synthesis of metal selenide nanocrystals based on the injection of selenium powder in a hot mixture containing the metal cation precursor complexed by a carboxylic acid is demonstrated by means of the formation of CdSe and ZnSe nanocrystals. In both cases, the synthesis can reach reaction yields of 80–85% within 5 min. In the case of CdSe nanocrystals, a more extensive study shows that even without protective atmosphere, the synthesis leads to state-of-the-art nanocrystals with low size dispersion. Importantly, the size of the nanocrystals at close to full yield can be changed by varying the carboxylic acid chain length, whereas the solid loading, that is, the amount of nanocrystals formed over the reaction volume, of the synthesis can be the 10-fold of typical literature syntheses. The potential of this reaction for the scaled up production of metal selenide nanocrystals is discussed and supported by the automated, parallel synthesis of CdSe nanocrystal batches using this heterogeneous selenium precursor where the standard deviation on the nanocrystal diameter is less than 1.5%.

Biofuels and additives: Comparative kinetic study of Amberlite IR 120-catalyzed esterification of ethanol with acetic, propanoic and pentanoic acids to produce eco-ethyl-esters

The effect of reaction time and operating parameters like temperature, catalyst loading and feed ratios on Amberlite IR 120-catalyzed esterification of ethanol with acetic, propanoic and pentanoic acids is studied. All three esterifications are slightly endothermic. The kinetic results are presented in the form of surface response plots. Relative increase in initial rates with increase in temperature depends on the steric hindrance around the carboxylic group. Ethanol feed ratios ranging from 0.3 to 0.6 exhibit the fastest initial rates. Catalyst efficiency is found to decrease significantly with increase in carboxylic acid chain length. Modified UNIFAC (Dortmund) model is used to predict system non idealities. An Eley Rideal mechanism, with surface reaction between adsorbed ethanol and acid in the bulk as the limiting step, best correlates the kinetic data.

Selective detection of dopamine in urine with electrodes modified by gold nanodendrite and anionic self-assembled monolayer

The determination of dopamine (DA) in urine is a promising technique for non-invasive DA monitoring, but current electrochemical techniques face substantial interference from uric acid (UA). This study applies three-dimensional gold nanodendrite (Au-DT) and self-assembled monolayer (SAM) to modify gold electrodes to improve their sensitivity and specificity to DA and alleviate UA interference. With the optimal ω-mercaptoalkane carboxylic acid chain length, the differential pulse voltammograms of Au-DT deposited electrode coated with 8-mercaptooctanoic acid (MOA) exhibit two voltammetric peaks that represent the oxidation potentials of DA and UA, respectively, with a separation of 260mV. Amperometric measurements show that the response current of Au-DT/MOA linearly depends on DA in the range of 0.01–5μM. The sensitivity of the Au-DT/MOA modified electrode is 20-fold that of the MOA-coated electrode. The proposed electrode has a low detection limit of 20nM for DA at a signal to noise ratio of 3 and resistance to UA interference, showing no response current with UA addition and no obvious decrease in the sensitivity of DA detection in the presence of UA. Moreover, the performances of the developed electrode, including sensitivity, recovery, and reproducibility, are validated for detecting DA in non-diluted human urine, with satisfactory results.

Carboxylic acid가 CuInS2/ZnS 반도체 나노입자의 광학적 특성에 미치는 영향

We report the effect of the chain length of carboxylic acid on the photoluminescence(PL) of /ZnS nanocrystals. /ZnS nanocrystals with emission wavelength ranging from 566 nm through 583 nm were synthesized with zinc acetate and carboxylic acids with various chain length. In this study, /ZnS nanocrystals prepared using long chain carboxylic acid showed more improved PL intensity. The origin of strong photoluminescence of the nanocrystals prepared with zinc acetate and long chain carboxylic acid was ascribed to improved size distribution due to strong reactivity between long chain carboxylic acid and zinc acetate.

Microelectrodes with gold nanoparticles and self-assembled monolayers for in vivo recording of striatal dopamine

Electrochemical determination of in vivo dopamine (DA) using implantable microelectrodes is essential for monitoring the DA depletion of an animal model of Parkinson's disease (PD), but faces substantial interference from ascorbic acid (AA) in the brain area due to similar electroactive characteristics. This study utilizes gold nanoparticles (Au-NPs) and self-assembled monolayers (SAMs) to modify platinum microelectrodes for improving sensitivity and specificity to DA and alleviating AA interference. With appropriate choice of ω-mercaptoalkane carboxylic acid chain length, our results show that a platinum microelectrode coated with Au-NPs and 3-mercaptopropionic acid (MPA) has approximately an 881-fold specificity to AA. During amperometric measurements, Au-NP/MPA reveals that the responsive current is linearly dependent on DA over the range of 0.01-5 μM with a correlation coefficient of 0.99 and the sensitivity is 2.7-fold that of a conventional Nafion-coated electrode. Other important features observed include fast response time (below 2 s), resistance to albumin adhesion and low detection limit (7 nM) at a signal to noise ratio of 3. Feasibility of in vivo DA recording with the modified microelectrodes is verified by real-time monitoring of electrically stimulated DA release in the striatum of anesthetized rats with various stimulation parameters and administration of a DA uptake inhibitor. The developed microelectrodes present an attractive alternative to the traditional options for continuous electrochemical in vivo DA monitoring.

Nanoparticles Change the Ordering Pattern of n-Carboxylic Acids into Nanorods on HOPG

This paper describes the formation of organic nanorods induced by monolayer-protected inorganic nanoparticles. Alkanes and alkane derivatives, such as n-carboxylic acids, self-assemble on highly oriented pyrolytic graphite (HOPG) into a persistent molecular packing structure that is dictated by the epitaxial interaction between the carbon chain plane and the HOPG basal plane. Carboxylic acids form 2-D crystalline layers consisting of nanostripe domains whose periodicity is one or two times the molecular chain length. However, when the molecular ordering occurs in the vicinity of a nanoparticle, this persistent HOPG-dominated nanostripe pattern is disrupted, and nanorods attached to the nanoparticles become the dominant structure. In order to understand the underlying mechanism of the nanoparticle-mediated nanorod formation, the effects of film-forming conditions, carboxylic acid chain length, nanoparticle size, and chemical composition of the nanoparticle are examined. It is determined that carboxylic acid nanorods can be induced by nanoparticles of different core materials including CdSe, CdS, and Au, as long as the protecting monolayer allows sufficient dispersion and colloidal stability of the nanoparticles in solution. A carboxylic chain length range amenable to the nanorod formation is identified, as is the relationship between the nanoparticle size and the number of nanorods per nanoparticle. This study contributes to the understanding of seed-mediated crystallization and molecular ordering. Moreover, it defines the parameters governing solution-based formation of hybrid nanostructures and nanopatterns incorporating dual functionality as defined by the inorganic nanoparticle and organic nanorod, respectively.

Incorporation of Fluorescent-Labeled Non-α-Amino Carboxylic Acids into the N-Terminus of Proteins in Response to Amber Initiation Codon

Abstract Incorporation of non-natural amino acid derivatives containing fluorescent groups into proteins is a useful method for protein analyses. Here, we investigated the incorporation of fluorescent-labeled non-α-amino carboxylic acids into the N-terminus of proteins in response to the UAG initiation codon. A series of TAMRA-labeled amino carboxylic acids were synthesized and attached to an amber suppressor initiator tRNA derived from Escherichia coli initiator tRNA. Fluorescent-labeled amino carboxylic acids were successfully incorporated into the N-terminus of streptavidin by adding TAMRA-acylated initiator tRNAs to an E. coli cell-free translation system, although the incorporation efficiency differed depending on the amino carboxylic acid chain length. Based on this observation, 3-aminopropionic acid derivatives labeled with BODIPY, rhodamine, and cyanine fluorophores were designed and synthesized. The fluorescent-labeled 3-aminopropionic acid derivatives developed using BODIPY and rhodamine dyes could be incorporated with good efficiency. On the other hand, 6-aminohexanoic acid was effectively incorporated when labeled with cyanine dyes. The present study demonstrates that translation initiation can accept a wide variety of non-natural substrates and provides a useful method for N-terminal-specific labeling of proteins with various fluorophores.

Development of a simple aqueous solution based chemical method for synthesis of mesoporous γ-alumina powders with disordered pore structure

A technically simple chemical method for the synthesis of mesoporous γ-alumina has been reported. Mesoporous γ-aluminas with different pore structure and surface area were synthesized by using aluminium nitrate as a source of aluminum. Supramolecular liquid crystalline phase of acid soap template synthesized via reaction of different carboxylic acids (stearic acid, oliec acid and lactic acid) with excess of triethanolamine (TEA) acts as a structure directing agent and water was used as solvent. Precursors were calcined at 550 °C in air for 2 h to obtain mesoporous alumina powders. Synthesized γ-alumina powders were characterized by using thermogravimetric analysis, X-ray diffraction, high resolution transmission electron microscope and N2 adsorption–desorption surface area and pore size analyzer. Pore size and ordering of pores were influenced by the chain length of carboxylic acids. Surface area of synthesized alumina powders varied from 214 to 376 m2/g and average pore diameter from 3.3 to 6.5 nm depending upon the chain length of the carboxylic acid.

Deuterium exchange and mass spectrometry reveal the interaction differences of two synthetic modulators of RXRα LBD

Protein amide hydrogen/deuterium (H/D) exchange was used to compare the interactions of two antagonists, UVI 2112 and UVI 3003, with that of the agonist, 9-cis-retinoic acid, upon binding to the human retinoid X receptor alpha ligand-binding domain (hRXRalpha LBD) homodimer. Analysis of the H/D content by mass spectrometry showed that in comparison to 9-cis-retinoic acid, the antagonists provide much greater protection toward deuterium exchange-in throughout the protein, suggesting that the protein-antagonist complex adopts a more restricted conformation or ensemble of conformations in which solvent accesses to amide protons are reduced. A comparison between the two antagonists shows that UVI 3003 is more protective in the C-terminal region due to the extra hydrophobic interactions derived from the atoms in the benzene ring of the carboxylic acid chain. It was less protective within regions comprising peptides 271-278 and 326-330 due to differences in conformational orientation, and/or shorter carboxylic acid chain length. Decreased deuterium exchange-in in the segment 234-239 where the residues do not involve interactions with the ligand was observed with the two antagonists, but not with 9-cis-RA. The amide protons of helix 12 of the agonist- or antagonist-occupied protein in solution have the same deuterium exchange rates as the unliganded protein, supporting a suggestion made previously that helix 12 can cover the occupied binding cavity only with the cofactor present to adjust its location.