Mixture Of Carboxylic Acids Research Articles

The scent gland composition of the Mangshan pit viper, Protobothrops mangshanensis.

The Mangshan pit viper, Protobothrops mangshanensis, is a rare, highly endangered snake native to the mountainous regions of Hunan Province in China. Snakes possess abdominal scent glands, which have been chemically studied in several species. These glands can contain various lipids and peptides, but very often also complex mixtures of carboxylic acids. We report here the occurrence of novel methyl-branched unsaturated acids found in the secretions of six captive individuals living in a zoo. The structures of these compounds, 4.6-dimethylalk-5-enoates in a homologous series from C11-C16, were characterized by GC-MS and GC-IR analysis and various microderivatization reactions including hydrogenation and esterification leading to methyl and pyridylmethyl esters. In addition, dimethyloxazoline formation helped to localize the double bond. The synthesis of methyl 4,6-dimethyldodec-5-enoate allowed the correct assignment of structures and showed the (E)-configuration of the double bond for the major naturally occurring diastereomers. These acids occur in small amounts compared to the major glandular components, cholesterol, and 1-O-hexadecylglycerol, as well as other common long-chain alcohols and amides. Although a general defensive function has been proposed for snake abdominal scent glands, the specific chemistry and moderate amounts of acids reported here may suggest a function in chemical signaling for the Mangshan pit viper. In addition, proline-containing diketopiperazines were identified for the first time in snake scent glands, although an artificial formation from amino acids likely present in the secretion cannot be excluded.

Flotation of Li Pegmatite with a Soybean Oil-Based Collector: Fundamental Studies

ABSTRACT In this work, the effect of a soybean oil-based collector on the surface properties of spodumene, feldspar, quartz, and muscovite was characterized and evaluated. By means of gas chromatography, it was determined that the reagent was composed of a mixture of carboxylic acids: linoleic (48%), oleic (28%), palmitic (13.3%), stearic (3.6%), α-linolenic (3.4%), and elaidic (3.2%). The reagent contained ~14 ppm Ca (determined by inductively coupled plasma optical emission spectroscopy – ICP-OES) and a critical micellar concentration (CMC) of 100 mg/L. At pH 6, the spodumene recovery was 50–60% higher than the other mineral recoveries, ascribed to chemical adsorption of the collector ionic-molecular species, which has high hydrophobicity power, on Al3+ sites on the spodumene surface. For pH values >10, the recoveries of feldspar and quartz were higher than spodumene, due to their activation by hydroxyl and hydroxide of Ca and subsequent adsorption of ionic specimen of the collector. The electrokinetic potential curves of spodumene, feldspar, and muscovite with collector were shifted toward more negative values compared to their electrokinetic potential curves without reagent. Fourier transform infrared spectroscopy (FT-IR) showed chemical adsorption of the anionic species of the collector at pH 6 with the Al3+, Fe3+, and Ca sites on the surface of aluminosilicates and Ca for quartz.

Detecting naphthenic acids in oil sands process water with microbial electrochemical sensor: Impact of inoculum sources and quorum sensing autoinducer

This study presents the inaugural demonstration of a microbial electrochemical cell (MXC)-based biosensor for naphthenic acids (NAs) detection in oil sands process water (OSPW) from a mining site. During the calibration process, different operating parameters were evaluated, including standing times (3 – 12 hours) and charging durations (5 – 20 minutes) within the charging-discharging cycles. The observations ascertained that a combination of a 12-hour standing period followed by a 15-minute charging period yielded the optimal current output when measuring NA concentrations ranging from 4.98 to 24.9 mg/L in real OSPW samples (diluted to concentrations of 20–100 %). Subsequently, incorporating diverse inoculum sources from MXCs led to significant signal output improvements, with one sustained on a mixture of cyclohexane carboxylic acids, commercial naphthenic acids, and real OSPW, and another exposed to acetate medium for over four years. Moreover, integrating quorum sensing (QS) autoinducers (10 μM) increased the current generation, highlighting the potential for more sensitive detection capabilities. Ultimately, our MXC biosensor could enable a cost-effective and rapid detection of OSPW NAs, offering a potential alternative for environmental surveillance.

Carbon type and quantity regulate soil free-living nitrogen fixation through restructuring diazotrophic community

Free-living nitrogen fixation (FLNF) is a ubiquitous and significant source of new nitrogen in ecosystems. This process requires a substantial amount of energy, and as a result, the input of labile carbon to soils may enhance FLNF. Here, we aim to explore the precise influence of different types and quantities of carbon on FLNF. We conducted experiments where sugars, carboxylic acids, and amino acids (common labile carbon inputs via root exudates) were added to cropland and forest soils. We monitored the changes in FLNF rate and diazotrophic community in response to these additions. Our findings revealed that sugars and carboxylic acids significantly stimulated FLNF rate, with an increase of up to three orders of magnitude, while amino acids either restricted FLNF or had no effect. When a mixture of sugars and carboxylic acids was added, the stimulation of FLNF was not observed until a threshold quantity of carbon was reached, indicating competition between diazotrophs and other microbes. Furthermore, the enhanced FLNF rate following carbon addition was attributable to shifts in diazotrophic community composition (e.g., increased abundance of Paenibacillus, a genus frequently used as biofertilizers), rather than to changes in the overall abundance of diazotrophs (reflected by nifH gene copy number). Our findings highlight the significant role of carbon type and quantity in regulating soil FLNF, partly through restructuring the diazotrophic community. The results have implications for predicting the response of rhizosphere FLNF to shifts in root exudation under environmental changes and can contribute to the application of diazotrophic biofertilizers in sustainable agriculture.

Formic and lactic acids from the conversion of xylose with the use of modified clinoptilolite by sonication

AbstractBACKGROUNDA material of natural origin, clinoptilolite, was modified with selected metals in order to obtain a catalyst for the conversion of xylose – the main component of the hemicellulose fraction present in lignocellulosic biomass – to selected carboxylic acids.RESULTSThe starting material without modification (0‐parent), the hydrogen form (0‐hydrogen) of zeolite and zeolite after hierarchization with hydrochloric acid (0‐dealuminated) were used. Iron, copper and cobalt ions were introduced as active centers using the sonication technique. The catalytic process was carried out in a pressure autoclave for 2 h at a temperature of 220 °C. Compounds such as formic acid with a yield of 91% (0‐parent) and lactic acid with a yield of 66.1% (Fe‐hydrogen) were obtained.ConclusionThe catalytic processes carried out using xylose lead to the obtaining of a mixture of carboxylic acids: lactic acid, pyruvic acid and formic acid. An important role here is played by the presence of iron as an active site, which leads to the transformation of xylose into lactic acid by dehydration, and the presence of Lewis and Brønsted active sites. In the case of formic acid, which has never been reported in publications on a similar topic, the starting zeolite without modification contributed to its preparation. It is possible that the content of alkali metals contributed to its preparation along with the coupling of the oxidation reaction of the intermediate product, because of the presence of small amounts of iron, which are present in the natural material. © 2024 Society of Chemical Industry (SCI).

Thermo physical and spectroscopic properties of binary liquid mixtures at various temperatures and correlation with the Jouyban–Acree model (propargyl alcohol, ethanoic acid, propanoic acid and butanoic acid)

ABSTRACT A thorough investigation into binary mixtures of propargyl alcohol and various carboxylic acids (ethanoic, propanoic and butanoic) was conducted. Measurements of density (ρ), speed of sound (u) and viscosity (η) were meticulously performed across the entire range of mole fractions at temperatures (303.15 K−313.15 K) and atmospheric pressure (0.1 MPa). These data were used to calculate key thermodynamic and transport properties, including excess molar volume, excess isentropic compressibility, deviation in viscosity and excess Gibbs free energy of activation for viscous flow. The partial molar properties and infinite dilution molar partial properties were also determined for each binary system. Trends and behaviours were interpreted within the framework of intermolecular interactions, focusing on complex formation and specific chemical forces. The PFP theory and Jouyban–Acree model were critically applied, with confidence in the findings supported by FTIR studies.

Solvent stabilizing effects on the order-disorder transition of schizophyllan in aqueous mixtures of carboxylic acids.

Schizophyllan is a triple helical β-1,3-D-glucan, and shows the cooperative order-disorder transition in the aqueous solution at the triple helix state. In this paper, the solvent stabilizing effects of two carboxylic acids, acetic acid and citric acid, on the cooperative order-disorder transition of aqueous schizophyllan solution were investigated from DSC and SEC-MALS measurements. The transition temperature (Tr) was shifted to higher temperature with increasing the molar fraction of carboxylic acid in the mixture (x). The transition enthalpy (ΔHr) was increased with increasing x. These solvent stabilizing effects indicate that these carboxylic acid molecules were selectively associated with the branched side chains of schizophyllan to stabilize the ordered state. The composition dependencies of Tr and ΔHr were analyzed by the linear cooperative transition theory to estimate the association parameters between the side chains and carboxylic acid. The theoretical parameters obtained were compared with those for the other active substances for the transition to discuss the molecular interactions between the triple helix and carboxylic acid.

Efficient Leaching of Metal Ions from Spent Li-Ion Battery Combined Electrode Coatings Using Hydroxy Acid Mixtures and Regeneration of Lithium Nickel Manganese Cobalt Oxide

Extensive use of Li-ion batteries in electric vehicles, electronics, and other energy storage applications has resulted in a need to recycle valuable metals Li, Mn, Ni, and Co in these devices. In this work, an aqueous mixture of glycolic and lactic acid is shown as an excellent leaching agent to recover these critical metals from spent Li-ion laptop batteries combined with cathode and anode coatings without adding hydrogen peroxide or other reducing agents. An aqueous acid mixture of 0.15 M in glycolic and 0.35 M in lactic acid showed the highest leaching efficiencies of 100, 100, 100, and 89% for Li, Ni, Mn, and Co, respectively, in an experiment at 120 °C for 6 h. Subsequently, the chelate solution was evaporated to give a mixed metal-hydroxy acid chelate gel. Pyrolysis of the dried chelate gel at 800 °C for 15 h could be used to burn off hydroxy acids, regenerating lithium nickel manganese cobalt oxide, and the novel method presented to avoid the precipitation of metals as hydroxide or carbonates. The Li, Ni, Mn, and Co ratio of regenerated lithium nickel manganese cobalt oxide is comparable to this metal ratio in pyrolyzed electrode coating and showed similar powder X-ray diffractograms, suggesting the suitability of α-hydroxy carboxylic acid mixtures as leaching agents and ligands in regeneration of mixed metal oxide via pyrolysis of the dried chelate gel.

Unravelling competitive adsorption phenomena in the aqueous phase reforming of carboxylic acids on Pt catalysts: An experimental and theoretical study

Biorefinery-derived wastewater is considered a valuable source of energy and chemicals thanks to its organic loading. However, it is constituted by different compounds which influence the performance of a catalytic valorization process. In this work, we investigated the treatment of a synthetic hydrothermal liquefaction-derived wastewater (HTL-WW) via aqueous phase reforming (APR) to obtain hydrogen. As a case study, we examined the underlying driving forces for performance differences in the APR of mono- and bi-component solutions of carboxylic acids as a model corn stover HTL-WW over Pt catalysts via a combined experimental and theoretical approach. In mono-component solutions, the conversion ranked as glycolic acid > propionic acid ≈ acetic acid, and the same was found for the hydrogen production tendency. Binary solutions of glycolic and acetic acid, with different concentration among the constituents, showed a strong inhibition of the acetic acid reactivity due to the prevalent adsorption of glycolic acid on Pt surface. The results from the APR of acetic and propionic acid solutions were less affected by such phenomena. DFT results showed that there are strong, attractive lateral interactions between carboxylic acids due to intermolecular hydrogen bonding that cause all carboxylic acids to preferentially adsorb in dimer structures. The lateral interaction strength was determined for both pure and binary mixtures of carboxylic acid dimers, with results showing that pure mixtures of carboxylic acids have stronger attractions and that glycolic acid dimers see the strongest attractions due to the added terminal hydroxyl functional group. The findings presented herein offer significant insights into the utilization of APR for industrial-like multi-component solutions, as well as for any catalytic process involving small organic compounds in an aqueous phase.

Improving plant availability of recycled phosphorus with organic acids

Increasing the efficiency of phosphorus (P) use through nutrient circularity is essential for securing P sufficiency and reducing pollution. The release of P in recycled materials can be enhanced with organic acids produced from cellulose. In this study, fertilisers based on sewage sludge (SS) and poultry manure (BR) were treated with increasing levels (0 %, 8 %, and 20 %) of hydroxy carboxylic and carboxylic acid mixture to determine the effect of acidification on the availability of P and other selected elements. According to sequential extractions, acidification increased the share of labile P in both products. In SS, which was dominated by refractory metal phosphates, a higher acid dose was required for the effect, and a smaller share of total P was transformed than in the BR, which was already rich in easily accessible P. Besides P, acidification increased the mobility of several elements but induced no harmful element accumulation in ryegrass leaves. The increased P lability recorded by fractionation in SS was reflected in ryegrass P uptake, cumulative yield, apparent P recovery, and mineral-P equivalence. In BR exhibiting superiority to mineral P, the effect of acidification on plant growth and P uptake was negative. Acidification treatment offers an option to enhance the plant availability of circular P, but the treatment needs to be tailored according to product characteristics. Optimising the application rate and acid composition might allow increasing effectiveness while avoiding negative growth effects.

2,2′-Biphenol-Derived Phosphoric Acid Catalyst for the Dehydrative Esterification of Carboxylic Acids with Alcohols

AbstractA dehydrative esterification from an equimolar mixture of carboxylic acids and primary or secondary alcohols in toluene at 100 °C was promoted without the necessity to remove water by using a simple 2,2′-biphenol-derived phosphoric acid catalyst (2.5–10 mol%). This reaction was also successfully conducted at the gram scale. To demonstrate the synthetic utility of this catalytic system, pharmaceutically useful substrates and acid-sensitive substrates were examined using these acid–base cooperative phosphoric acid catalysts, which exhibit relatively weak Brønsted acidity.

Selective pertraction of dicarboxylic acids from simulated Rhizopus oryzae fermentation broths

Fumaric, malic and succinic acids have been selectively separated by facilitated pertraction with Amberlite LA-2, using n-heptane as liquid membrane. The feed phase consisted on viscous aqueous solution with similar mixture of carboxylic acids and viscosity as those of Rhizopus oryzae fermentation broth. Due to the differences between the acidities and molecule size of these acids, it is possible to selectively recover fumaric acid from the initial solution. The pH-gradient between the feed and stripping phases, as well as carrier concentration in the liquid membrane represent the main process parameters influencing the pertraction selectivity. Among them, Amberlite LA-2 concentration exhibits the most important control on the selectivity factor S, the maximum value of S being reached for carrier concentration of 30 g/l. The increase of feed phase viscosity amplified the magnitude of these influences on pertraction selectivity, due to the hindrance of acids diffusion towards the region where their reaction with Amberlite LA-2 occurs, effect more important for malic acid. Therefore, by modifying the viscosity from 1 to 24 cP, the maximum value of selectivity factor was increased from 12 to 18.8.

Automated Liquid–Liquid Microextraction of Fluoroquinolones for Their Subsequent Chromatographic Determination

An automated method is developed for dispersive liquid–liquid microextraction of fluoroquinolone antibiotics based on the principles of stepwise injection analysis. The method involves the dispersion of the extractant by the gas phase, formed in situ in the extraction chamber of the flow analyzer. A deep eutectic solvent based on a terpenoid and a mixture of hydrophilic and hydrophobic carboxylic acids is studied as an extractant for the isolation and preconcentration of fluoroquinolones, and a possibility of its use is substantiated. Hydrophilic carboxylic acid in the composition of the extractant acts as a proton donor for the formation of a carbon dioxide dispersant in the presence of sodium carbonate dissolved in the aqueous phase. A possibility of combining the developed method with high-performance liquid chromatography with fluorimetric detection is shown on an example of the determination of fluoroquinolones in wastewaters. The limits of detection (3σ) for ofloxacin, fleroxacin, and norfloxacin were 0.3 µg/L.

Protic ionic liquids based on fatty acids: A mixture of ionic and non-ionic molecules

Fatty acids are long chain carboxylic acids naturally and abundantly found in oils and fats; therefore, they are interesting candidates for protic ionic liquids (PILs) synthesis. Mixtures of carboxylic acids and amines should lead to intermediate proton transfer from the acid to the amine to form PILs, with both ionic molecules (PIL) and non-ionic molecules observed in these mixtures, depending on the nature of the amine. This work studied the physicochemical properties of mixtures between fatty acids and amines, with phase transitions, thermal stability, viscosity, solvation (Kamlet-Taft parameters) and proton transfer evaluated. Our results show that like other carboxylic acids the proton transfer is highly dependent on the structure of the amine, being much higher for primary amines than for tertiary amines. Also, hydroxyl groups on tertiary amines increase the proton transfer. The extent of the proton transfer strongly influences the physicochemical properties of the mixtures, where a larger proton transfer leads to a higher melting point and higher viscosity. Also, mixtures based on highly volatile amines decomposed at low temperatures even when a high degree of proton transfer was observed. Surprisingly, mixtures based on butylamine or triethylamine exhibited high hydrogen bond acceptor capacity and low dipolarity-polarizability which is an unusual characteristics of ionic liquids, potentially opening new solvent application space for ionic liquids.

PRODUCTION OF ESTERS BY ETERIFICATION OF FATTY ACIDS OF SUNFLOWER, OLIVE AND SOYBEAN OILS WITH MANNITOL, SORBITOL AND XYLITOL

Polyol esters are widely used in various fields of science and technology, food industry, sanitation, medicine, cosmetics, etc. In engineering, polyol esters are mainly used as high-temperature lubricating oils․Esters of polyols with a degree of substitution from 1:1 to 3:1 are used as emulsifiers, stabilizers, defoamers, dispersants and detergents. Esters of saturated carboxylic acids С12 – С18 – with a degree of substitution from 4:1 to 6:1 are thick or hard oils and are used in medicine, pharmacy and cosmetology. In our early studies, with the esterification of mannitol and other C4 – C6 polyols with some higher aliphatic acids in molar ratios of 1: 3÷6, various esters were obtained. The synthesized oil-like products were similar in their physicochemical and rheological properties to natural fats and oils and had melting points in the range of –10...64 °C. However, differing from artificial oils, natural fats and oils contains variety of saturated and unsaturated fatty acids C6 – C12. Therefore, in order to obtain more natural oil and fat substitutes, it seems appropriate to obtain esters of higher polyols with a complex of natural fatty acids. This paper presents data on obtaining a complex of fatty acids of sunflower, olive and soybean oils and further synthesis of esters with mannitol, sorbitol and xylitol in molar ratios of 1: 3...6. The studies were carried out according to the following scheme: A) hydrolysis of sunflower, olive and soybean oils with an alkali solution, with the formation of a mixture of carboxylic acids, consisting mainly of oleic, linoleic, stearic and palmitic acids; B) neutralization of alkali salts, isolation and drying of fatty acids mixtures; C) esterification of mannitol, sorbitol and xylitol with fatty acid complexes; D) purification and drying of non-glyceride oils; E) determination of the main physicochemical properties of the obtained artificial oils. The reaction progress is monitored by HPLC method on an Agilent Infinity II HPLC 1260 System instrument and by IR spectra method on an IKS 29 instrument. The completion of polyol esterification reactions with fatty acid complexes is determined by the disappearance of absorption bands in the IR spectra in the region of 1740 and 2500...2700 cm˗1. Outputs of artificial oils in optimal conditions reach 95-97%. Non-glyceride oils are intended for testing as substitutes for natural oils and fats.

Flotation separation of titanite concentrate from apatite-nepheline-titanite ores of anomalous zones of the Khibiny deposits

Titanium raw materials are widely used for the synthesis of various functional materials – sorbents of radionuclides and rare earth elements, various additives, filler pigments, etc. Since most of titanium concentrates are imported, in line with the import substitution program, production of titanite concentrate from apatite-nepheline ores of the Khibiny deposits is a promising trend for supplying national industry with titanium raw materials. The article presents the results of laboratory studies of flotation separation of titanite concentrate from apatite-nepheline-titanite ores extracted from the upper ore horizon of the Koashvinskoye deposit, where titanite-enriched ores are concentrated. Recovery of titanite concentrate was accomplished using two reagent modes – a mixture of alkyl hydroxamic and carboxylic acids with the addition of distilled tall oil and a mixture of tall oils with the addition of polyalkyl benzene sulfonic acids. The results of the research showed that the first flotation mode, which allows a selective recovery of titanite into the concentrate (titanite content in the concentrate was 93.5 %) is the most efficient. It was shown that flotation separation of titanite concentrate is preferable compared to the chemical method based on sulfuric acid leaching.

Optimized regimes of nepheline flotation using stockpiled apatite-nepheline processing waste (the Khibiny deposits)

The task of processing stockpiled apatite-nepheline waste is of relevance and in line with the goal of ensuring environmental safety in Russia’s Arctic zone achievable through the reduction of accumulated environmental damage. The cost of processing secondary raw materials — when no grinding is required and thus most energy costs are saved — is much lower in comparison with the processing of natural raw materials. Around 1 billion tons of flotation waste have accumulated in the tailings ponds of Apatit-owned concentrator plants over the 90-year history of exploiting the Khibiny deposits. It poses a real threat of toxic pollution. In this regard, the development of beneficiation processes aimed at reducing waste that goes in the tailings ponds should be considered a priority area of research in the field of mineral processing. This paper describes the results of an extended laboratory study that looked at the concentratibility of two samples of apatite-nepheline flotation waste taken from two tailings ponds owned by Apatit which have different storage times. It is shown that the main valuable minerals in the tailings include nepheline (more than 50%), pyroxenes (5–7%) and titanite (about 4%). Three reagent regimes of reverse flotation were used to obtain nepheline concentrate: a basic regime that uses a mixture of coniferous and deciduous tall oil; a regime that uses alkyl hydroxamic acids to which distilled tall oil is added, and a regime that uses a mixture of tall oil and polyalkyl benzene sulfonic acids. The findings suggest that the regime that uses the mixture of alkyl hydroxamic and carboxylic acids with the addition of distilled tall oil provides the most efficient flotation regime that helps to selectively separate nepheline and darkcoloured minerals from the long-term storage tailings. The paper demonstrates feasibility of using apatite-nepheline processing waste (a case study of the Khibiny deposits) to produce nepheline concentrate, which serves as a material that can substitute imported non-bauxite raw materials required by aluminium industry.

Micellar and sub-micellar chromatography with a cocamidopropyl betaine surfactant

We have coated a typical C18 column with the pH cationic charge controllable zwitterionic synthetic surfactant, cocamidopropyl betaine (CAPB), in order to generate a mixed mode reversed phase weak ion exchange column. As determined by the Thomas model, the column has an adsorbed surfactant capacity of 0.557 mmoles. The addition of 8.8 × 10–4 M CAPB to the totally aqueous mobile phase ensured stability of the surfactant on the column and permitted separation of the four component sulfonamide mixture with micellar liquid chromatography (MLC) in under 11 min. Comparatively, with a dilute H2SO4 mobile phase with no CAPB, the separation time for the sulfonamide mixture reached an excessive run time of an hour on the bare C18 chains. With CAPB in the mobile phase (no organic solvent present), a seven component sulfonamide mixture could be separated in less than 45 min. A five component short chain carboxylic acid mixture, separated in 20 min, was used to examine the ion exchange character of the column in pH environments of 2.3 and 4.6. Three phase MLC equilibrium analysis was also done in these pH environments with the sulfa drug and carboxylic acid mixtures to determine partition coefficients. Finally, a quite high molecular weight (70,000) anionic polystyrene sulfonate polymer was characterized by MLC with only CAPB and variable pH mobile phases; the optimal pH was determined to be 5.6. A totally aqueous mobile phase without CAPB was not suitable for profiling this polymer.

Effect of ferrate pretreatment on anaerobic digestibility of primary sludge spiked with resin acids.

Resin acids are mixtures of high molecular weight carboxylic acids found in tree resins. Due to higher hydrophobicity and low solubility, they tend to adsorb on the suspended solids in pulp and paper (P&P) mill wastewater and accumulate in primary sludge through settling. Anaerobic digestion (AD) is a common practice stabilizing sludge; however, high concentration of resin acids affects the AD process. The aim of this research was mainly to determine the impact of ferrate (Fe (VI)) oxidation on selected resin acids and anaerobic digestibility of ferrate-treated primary sludge (PS) spiked with the resin acids. First, batch control oxidation of model resin acids with Fe (VI) was conducted to identify an optimum dosage, pH and contact time using a Box-Behnken design approach. Thereafter, anaerobic treatability studies of primary sludge spiked with resin acids both under control condition and optimum ferrate pretreatment were conducted. Up to 97% oxidation of resin acids occurred in pure water, while only 44%-62% oxidation of resin acids occurred in PS with an increasing Fe (VI) dosage from 0.034 to 0.137mg Fe (VI)/mg tCODfed. The pretreatment did not affect the anaerobic biodegradability of resin acids; however, it lowered their negative influences on the PS digestibility. About 0.076mg Fe (VI) dosage/mg tCODfed solubilized the sludge increasing the methane production by 40% compared to the untreated digester. The potential benefits of ferrate pretreatment of P&P primary sludge include resin acids oxidation and subsequent toxicity reduction, higher sludge solubilization enhancing methane production and enabling anaerobic digestion at higher COD loading.

Surface tension of binary mixtures of benzene + propionic acid and butanoic acid between 298.15 K and 318.15 K: Measurement and modeling

Experimental measurement of the surface tension of benzene + propanoic acid and benzene + butanoic acid has been carried out in the temperature range of 298.15 K to 318.15 K and atmospheric pressure. 170 new experimental points of surface tension have been obtained. Three theoretical models, i.e., Linear gradient theory (LGT), Shereshefsky model (SM), and the extended Langmuir model (LM), were used to modeling the surface tension and adsorption phenomenon of these binary mixtures. The three models correlated the surface tension of the benzene + carboxylic acid mixtures, and the average percent deviation was, 0.04% for LGT, 0.08% for SM, and 0.05% for LM. The Helmholtz density term and the liquid and vapor densities required in computing density with LGT were obtained with perturbed chain-statistical associating fluid theory equation of state (PC-SAFT EOS). Based on SM, the standard Gibbs energy of adsorption and the free energy change in the surface region were calculated. The free energy change was used to obtain the excess number of molecular layers in the surface region. The required parameters of the LM were adjusted, the standard Gibbs energy of adsorption was calculated, and negative deviations from ideality were determined. Also mole fractions of solute 0at surface were calculated by using LM. Additionally, by using surface tensions at different temperatures, specific surface enthalpy and specific surface entropy were calculated for (benzene + carboxylic acid) mixtures.