Short-chain Aliphatic Carboxylic Acids Research Articles

Molecular simulations of liquid aliphatic carboxylic acids (C1-C6) using the 3D-RISM-KH molecular solvation theory

The liquid structures of short straight chain aliphatic carboxylic acids (C1-C6) and halogenated acetic acids (trifluoro and trichloro) are analyzed with molecular dynamics simulations, three-dimensional reference interaction site model, and density functional theory calculations. The neat acids are found to exist in multimeric ordered form consisting of both open chain and cyclic oligomers. Introduction of water breaks the hydrogen bonding networks between adjacent acetic acid molecules by inserting water as a bridging molecule. The electronic structure calculations confirm the formation of chain and ring type structures in the liquid state.

Liquid chromatography of short chain carboxylic acids using a glutamic acid surfactant coated C18 stationary phase

A C18 column was modified with the anionic amino acid surfactant lauroyl-l-glutamate (LLG) to facilitate the separation of ten short-chain aliphatic carboxylic acids (oxalic, tartaric, malic, malonic, lactic, acetic, maleic, citric, fumaric, and succinic). The developed method was proven to be fast, versatile, and environmentally friendly. After the coating of the column using 1% LLG solution and optimizing chromatographic conditions such as pH and temperature, near baseline resolution of the ten carboxylic acids within 4 min with excellent peak shape at pH = 1.8 using 100% H2O acidified with sulfuric acid was possible. Although the design of this stationary phase, with the hydrophilic group at the end of the alkyl chain, seems to be in contrast to such columns designed for a totally aqueous mobile phase that have a polar (often amide) group embedded near the silica surface, no evidence of phase collapse was noted. Linear relationships of ln retention factor (k) versus 1/Temperature (T) (van't Hoff plots) were generated for all the acids indicating a single retention mechanism was likely. As the pH of the mobile phase decreased, the analyte retention factors increased due to the increase of the fraction of the analyte with neutral charge (alpha zero). The surfactant amide linkage, being electron donating, increased the pKa of the more acidic carboxyl group of glutamic acid so both carboxyl groups were protonated (neutral) at pH 1.8. The exact nature of the retention mechanism is uncertain but there certainly seems to be a pronounced hydrophobic component due to the large difference in retention of fumaric acid and methyl fumarate at pH 1.8. In addition, eleven beverage samples were analyzed for their aliphatic carboxylic acid contents. The results showed that malic, fumaric, and citric acids were the most common carboxylic acids in natural beverages with concentrations as high as 6432 ppm of malic acid in organic apple juice, 64 ppm of fumaric acid in organic concord juice, and 6543 ppm citric acid in strawberry lemonade juice.

Retention time modeling of short-chain aliphatic acids in aqueous ion-exclusion chromatography systems under several conditions using computational intelligence methods (artificial neural network and adaptive neuro-fuzzy inference system)

In this paper, computational intelligence methods such as Artificial Neural Network (ANN) and Adaptive Neuro-Fuzzy Inference System (ANFIS) were used to model the effective parameters on retention behaviour of short-chain aliphatic carboxylic acids (C1-C6) and predict their retention time. For this purpose, seven factors, in three different categories, have been considered as input parameters in modeling and prediction of retention time: (i) operational parameters (temperature, H2SO4 normality as a mobile phase concentration, and flow rate); (ii) column characteristic properties (length of column, width of column, column’s particle size as the size of stationary phase); and (iii) acid type (number of carbon atoms in the analyte acid). Experimental data of available literatures were used as a data set to train and test Computational Intelligence (CI) methods. After developing the models, prediction ability of the models was checked with additional 18 data sets. The obtained results of the models showed that the proposed models are very precise, efficient and useful for fast and accurate prediction of the retention time for aliphatic carboxylic acids. Comparison of the two approaches indicated that both methods provide good results. Root mean square error of 0.0255 and 0.004, sum of square error of 0.148 and 0.001, and correlation factor of 0.978 and 0.998 for ANN and ANFIS, respectively, demonstrated that the proposed ANFIS model is more accurate in compared to the ANN model.

Use of RSM for the multivariate, simultaneous multiobjective optimization of the operating conditions of aliphatic carboxylic acids ion-exclusion chromatography column: Quantitative study of hydrodynamic, isotherm, and thermodynamic behavior

The present study evaluates the capability of ion exclusion chromatography (IEC) of short chain aliphatic carboxylic acids using a cation exchange column (8% sulfonated cross-linked styrene-divinylbenzene copolymer) in different experimental conditions. Since one of the prerequisites to the development of an efficient carboxylic acid separation process is to obtain the optimum operational conditions, response surface methodology (RSM) was used to develop an approach to evaluate carboxylic acids separation process in IEC columns. The effect of the operating conditions such as column temperature, sulfuric acid concentration as the mobile phase, and the flow rate was studied using Central Composite Face (CCF) design. The optimum operating conditions for the separate injection of lactic acid and acetic acid is temperature of 75 °C, sulfuric acid concentration of 0.003 N for both acids and flow rate of 0.916 (0.886) mL/min for acetic acid (lactic acid). Likewise, the optimum conditions for the simultaneous injection of acetic and lactic acid mixture are the column temperature of 68 °C, sulfuric acid concentration of 0.0003 N, and flow rate of 0.777 mL/min. In the next step, the adsorption equilibria of acetic acid and lactic acid on the stationary phase were investigated through a series of Frontal Analysis (FA), Frontal Analysis by Characteristic Points (FACP), and using Langmuir isotherm model. The results showed an excellent agreement between the model and experimental data. Finally, the results of thermodynamic studies proved that the IEC process for separation of acetic and lactic acid is a spontaneous, feasible, exothermic, and random process with a physical adsorption mechanism.The results of the current paper can be a valuable information in the stages of designing IEC columns for separation of aliphatic carboxylic acids.

Application of electrochemical advanced oxidation to bisphenol A degradation in water. Effect of sulfate and chloride ions

Electrochemical oxidation with electrogenerated H2O2 (EO- H2O2), electro-Fenton (EF), photoelectro-Fenton (PEF) and solar PEF (SPEF) have been applied to mineralize bisphenol A solutions in 0.050 M Na2SO4 or 0.008 M NaCl + 0.047 M Na2SO4 at pH 3.0. The assays were performed in an undivided cell with a boron-doped diamond (BDD) anode and an air-diffusion cathode for continuous H2O2 production. The PEF and SPEF processes yielded almost total mineralization due to the potent synergistic action of generated hydroxyl radicals and active chlorine, in conjunction with the photolytic action of UV radiation. The higher intensity of UV rays from sunlight explained the superior oxidation ability of SPEF. The effect of applied current density was studied in all treatments, whereas the role of bisphenol A concentration was examined in PEF. Bisphenol A abatement followed a pseudo-first-order kinetics, which was very quick in SPEF since UV light favored a large production of hydroxyl radicals from Fenton's reaction. Eight non-chlorinated and six chlorinated aromatics were identified as primary products in the chloride matrix. Ketomalonic, tartronic, maleic and oxalic acids were detected as final short-chain aliphatic carboxylic acids. The large stability of Fe(III)-oxalate complexes in EF compared to their fast photomineralization in PEF and PEF accounted for by the superior oxidation power of the latter processes.

Removal of 4-hydroxyphenylacetic acid from aqueous medium by electrochemical oxidation with a BDD anode: Mineralization, kinetics and oxidation products

The degradation of 100mL of solutions containing 4-hydroxyphenylacetic acid in 0.050M Na2SO4 at pH3.0 has been performed by anodic oxidation with electrogenerated H2O2 (AO-H2O2) using a stirred tank reactor equipped with a boron-doped diamond (BDD) anode and an air-diffusion cathode. An almost total mineralization with 95.5% total organic carbon (TOC) removal was achieved for a 1.03mM substrate solution at 100mAcm−2. The effect of current density between 16.7 and 100mAcm−2 and 4-hydroxyphenylacetic acid content between 0.21 and 2.06mM was examined. Greater current efficiency with lower specific energy consumption and smaller mineralization was found at low current density and high substrate concentration. The TOC abatement as well as the 4-hydroxyphenylacetic acid concentration decay obeyed a pseudo-first-order kinetics. The oxidation role of hydroxyl radical formed from water discharge at the BDD anode is explained on the basis of its electrogeneration rate and competitive wasting reactions. 4-Hydroxybenzenemethanol and its derivative 4-hydroxybenzenealdehyde were identified as primary aromatic by-products by gas chromatography-mass spectrometry. Ion-exclusion HPLC allowed the detection of low amounts of the persistent oxalic acid during the AO-H2O2 process. The remaining TOC in final electrolyzed solutions is related to the presence of a large proportion of unidentified by-products that are even more recalcitrant than common short-chain aliphatic carboxylic acids.

Ion-Exclusion High-Performance Liquid Chromatography of Aliphatic Organic Acids Using a Surfactant-Modified C18 Column.

Ion exclusion chromatography (IELC) of short chain aliphatic carboxylic acids is normally done using a cation exchange column under standard HPLC conditions but not in the ultra-HPLC (UHPLC) mode. A novel IELC method for the separation of this class of carboxylic acids by either HPLC or UHPLC utilizing a C18 column dynamically modified with sodium dodecyl sulfate has been developed. The sample capacity is estimated to be near 10 mM for a 20 µL injection or 0.2 µmol using a 150 × 4.6 mm column. The optimum mobile phase determined for three standard mixtures of organic acids is 1.84 mM sulfuric acid at pH 2.43 and a flow rate of 0.6 mL/min. Under optimized conditions, a HPLC separation of four aliphatic carboxylic acids such as tartaric, malonic, lactic and acetic can be achieved in under 4 min and in <2 min in the UHPLC mode at 2.1 mL/min. A variety of fruit juice and soft drink samples are analyzed. Stability of the column as measured by the retention order of maleic and fumaric acid is estimated to be ∼4,000 column volumes using HPLC and 600 by UHPLC. Reproducible chromatograms are achieved over at least a 2-month period. This study shows that the utility of a C18 column can be easily extended when needed to IELC under either standard or UHPLC conditions.

Effect of short chain aliphatic carboxylic acids for sorption of uranyl on rutile Zeta potential and in situ ATR-FTIR studies

Migration of radionuclides in aqueous system is a matter of great environmental concern due to their acute and long-term toxicity. This study seeks to address the sorption of uranyl on rutile in presence of short-chain aliphatic carboxylic acids by zeta potential analysis and in situ ATR-IR spectroscopy. Point of zero charge of rutile was significantly shifted with the addition of carboxylic acids/uranyl ions separately in solution but it was negligible when organics and uranyl ions were added in the suspension. In situ ATR-IR data for uranyl sorption was evidenced by an absorption band of uranyl as(UO2) at 915cm−1.

Chemical oxidation of a malodorous compound, indole, using iron entrapped in calcium alginate beads

Iron-alginate beads (Fe-ABs) were successfully prepared by the ion-gelation method, and applied as heterogeneous Fenton catalysts for the removal of a malodorous compound ‘indole’. Similarly, copper-enriched alginate beads (Cu-ABs) were synthesized and tested as like-Fenton catalyst, however, their application proved not to be effective for this purpose. Fe-ABs catalysts were characterized by FTIR, SEM, EDS and AAS spectroscopy.Results pointed out that the parameters affecting Fenton catalysis must be carefully chosen to avoid excessive iron release. Under optimal conditions, complete indole removal and considerably high reduction of TOC, without significant leaching was achieved. Indole decay followed a pseudo-first-order kinetics. The absolute rate constant for indole hydroxylation was 3.59×109M−1s−1, as determined by the competition kinetics method.Four reaction intermediates (Isatin, Dioxindole, Oxindole and Anthralinic acid) were identified by ULC/MS/MS analysis. Short-chain aliphatic carboxylic acids like formic, acetic, oxalic, maleic, oxamic and pyruvic acids were identified by ion exclusion chromatography and as end-products. Based on the identified by-products, a plausible mineralization pathway was proposed. Moreover, the catalyst was recovered quantitatively by simple filtration and reused for several times without significant loss of activity.

Performance of a low-cost direct glucose fuel cell with an anion-exchange membrane

This paper reports on the use of renewable carbohydrate as a high-density energy source for electricity production under low temperatures. We have developed a two-chamber glucose alkaline fuel cell with a low-cost anion-exchange membrane. Methyl viologen (MV) and nickel foam were used as electrocatalyst for glucose oxidation reaction at the anode. Effects of various experimental parameters on the fuel-cell performance were investigated. The fuel cell achieved the maximum power density of 5.20 W m−2 at 15 mM MV, 3 M KOH, 1 M glucose, and 25 °C. The performance can be improved further by increasing operational temperature and concentrations of MV, KOH, and glucose. HPLC results show the main oxidation products are short-chain aliphatic carboxylic acids. Specific discharge capacity of glucose reached 153.58 ± 17.49 mAh g−1 in the fuel cell with AEM, which was 1.81-fold higher than without AEM.

Routes for the electrochemical degradation of the artificial food azo-colour Ponceau 4R by advanced oxidation processes

The performance of three electrochemical advanced oxidation processes, namely electro-oxidation with electrogenerated H2O2 (EO–H2O2), electro-Fenton (EF) and photoelectro-Fenton (PEF) for the treatment of aqueous solutions of the food azo dye Ponceau 4R in an undivided cell with a BDD anode and an air-diffusion cathode was compared in terms of colour, dye concentration and total organic carbon (TOC) removals. PEF treatments in ultrapure water with Na2SO4 were performed to assess the effect of current density, as well as supporting electrolyte and dye concentrations. At 100mAcm−2, solutions of 130mL of 254mgL−1 of the dye in 0.05M Na2SO4 became colourless and totally mineralized after 50 and 240min, respectively, which can be explained by the synergistic action of BDD(OH) at the anode surface and homogeneous OH formed in the bulk from Fenton’s reaction promoted in the presence of Fe2+ catalyst. Furthermore, UVA photons induced the continuous Fe2+ regeneration and photolytic decomposition of refractory intermediate complexes. In that aqueous matrix, the cleavage of the dye molecules proceeded through several reaction routes to yield N-containing and non-N-containing derivatives with one or two aromatic rings, short-chain aliphatic carboxylic acids and inorganic ions. Oxalic and oxamic acids and sulfate ions were accumulated at different rates in EO–H2O2, EF and PEF. The three methods allowed the progressive decontamination of Ponceau 4R solutions in a real water matrix even without the addition of electrolyte, although complete TOC abatement after 360min at 33.3mAcm−2 was only ensured by the iron-catalyzed PEF process.

Comparison of Processes for the Degradation of Trans-Cinnamic Acid: Anodic Oxidation, Electro-Fenton and Photoelectro-Fenton

INTRODUCTION Olive mill wastes worsen environmental problems in Mediterranean countries. These wastewaters contain phenolic compounds used as fragrances and artificial flavours and other compounds such as trans-cinnamic acid. The electrochemical techniques, especially the electrochemical advanced oxidation processes (EAOPs), are applied in many fields including the wastewater treatment. EAOPs are based on the in situ electrochemical generation of the hydroxyl radical (●OH), which has so high oxidizing power that it is able to yield dehydrogenated or hydroxilated derivatives that can be oxidized up to their complete mineralization. EXPERIMENTAL In this work, the degradation of trans-cinnamic acid was studied by means of various EAOPs. Solutions of 100 mL of this compound in 0.05 M Na2SO4 of pH 3.0 were comparatively treated by anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF) and photoelectro-Fenton (PEF) using a stirred tank reactor equipped with a 3 cm2 boron-doped diamond (BDD) anode and a 3 cm2 carbon-polytetrafluoroethylene air-diffusion cathode. In AO-H2O2, the acid and its intermediates were destroyed by ●OH formed at the BDD surface, whereas in EF the mineralization rate was enhanced by ●OH generated in the bulk from Fenton’s reaction between cathodically generated H2O2 and 0.5 mM Fe2+ added at the beginning of the experiment. In the case of PEF, the degradation process can be significantly enhanced under the photocatalytic action of UVA radiation provided by a 6 W artificial lamp. For each method, the influence of current density and trans-cinnamic acid content on TOC decay was examined. The results revealed that the PEF process was always the most efficient treatment, allowing an almost total mineralization of a 100 mg L-1 TOC solution of trans-cinnamic acid after 180 min of electrolysis at 33.3 mA cm-2. Generated short-chain aliphatic carboxylic acids as oxalic, acetic and fumaric in the above treatments were identified and quantified by ion-exclusion HPLC. RESULTS For all the EAOPs tested, TOC was gradually reduced at prolonged electrolysis. The oxidation ability increased in the sequence AO-H2O2 < EF < PEF. For each method, the mineralization was enhanced with increasing current density. PEF became the most potent method, yielding 98% mineralization after 180 min at 33.3 and 66.7 mA cm-2, which showed that UVA light was a powerful tool. TOC removal increased at a higher initial trans-cinnamic acid concentration, especially in the EF and PEF assays, thereby making the process much more efficient. HPLC chromatograms of electrolyzed solutions exhibited well-defined peaks related to oxalic (t r = 6.96 min), acetic (t r = 15.1 min) and fumaric (t r = 15.6 min) acids. The two latter acids are formed from the cleavage of the benzene ring of trans-cinnamic acid, being oxidized to oxalic acid that is directly and completely mineralized to CO2in 240 min by PEF. DISCUSSION Trans-cinnamic acid solutions can be decontaminated at pH 3 and 25 °C using a BDD/air-diffusion cell. This is due to the oxidation with ●OH formed from water oxidation at the BDD surface in AO-H2O2, the additional destruction with ●OH produced in the bulk from Fenton’s reaction between generated H2O2 and added Fe2+in EF, and the synergistic action of photolysis of Fe(III)-carboxylate complexes under UVA irradiation in PEF. The mineralization rate of trans-cinnamic acid increases in the order AO-H2O2 < EF < PEF under the same experimental conditions due to the larger production of ●OH and the action of UVA light. For each EAOP, higher mineralization rate was found at higher current density as a result of the higher generation of ●OH at the BDD surface and in the bulk, but the mineralization current efficiency decreased because of the enhancement of parasite reaction of ●OH. An increase in trans-cinnamic acid concentration caused a higher TOC removal with superior current efficiency due to the minimization of parasite reactions of ●OH by the presence of more organic matter. The destruction of the parent molecule and its intermediates yielded final short-chain carboxylic acids such as fumaric, acetic and oxalic. The latter was the most persistent but its Fe(III) complexes could be rapidly photodecomposed in PEF. The PEF process was the most potent EAOP giving rise to an almost total mineralization of solutions with 100 mg L-1 TOC of trans-cinnamic acid after 180 min at 33.3 mA cm-2. The EAOPs tested demonstrated their feasibility to decontaminate water containing trans-cinnamic acid, opening the door to develop more effective technologies for the treatment of olive mill wastewaters. ACKNOWLEDGEMENTS The authors are grateful to MINECO (Spain) for financial support from project CTQ2013-48897-C2-1-R, co-financed with FEDER funds. The scholarship given to N.E Flores from SENECYT (Ecuador) is also acknowledged.

Degradation of tyrosol by a novel electro-Fenton process using pyrite as heterogeneous source of iron catalyst

Tyrosol (TY) is one of the most abundant phenolic components of olive oil mill wastewaters. Here, the degradation of synthetic aqueous solutions of 0.30 mM TY was studied by a novel heterogeneous electro-Fenton (EF) process, so-called EF-pyrite, in which pyrite powder was the source of Fe2+ catalyst instead of a soluble iron salt used in classical EF. Experiments were performed with a cell equipped with a boron-doped diamond anode and a carbon-felt cathode, where TY and its products were destroyed by hydroxyl radicals formed at the anode surface from water oxidation and in the bulk from Fenton's reaction between Fe2+ and H2O2 generated at the cathode. Addition of 1.0 g L−1 pyrite provided an easily adjustable pH to 3.0 and an appropriate 0.20 mM Fe2+ to optimize the EF-pyrite treatment. The effect of current on mineralization rate, mineralization current efficiency and specific energy consumption was examined under comparable EF and EF-pyrite conditions. The performance of EF-pyrite was 8.6% superior at 50 mA due to self-regulation of soluble Fe2+ by pyrite. The TY decay in this process followed a pseudo-first-order kinetics. The absolute rate constant for TY hydroxylation was 3.57 × 109 M−1 s−1, as determined by the competition kinetics method. Aromatic products like 3,4-dihydroxyphenylethanol, 4-hydroxyphenylacetic acid, 4-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid and catechol, as well as o-benzoquinone, were identified by GC–MS and reversed-phase HPLC. Short-chain aliphatic carboxylic acids like maleic, glycolic, acetic, oxalic and formic were quantified by ion-exclusion HPLC. Oxalic acid was the major and most persistent product found. Based on detected intermediates, a plausible mineralization pathway for TY by EF-pyrite was proposed.

Total removal of alachlor from water by electrochemical processes

Concentrated aqueous solutions of the chloroacetanilide herbicide alachlor, a suspected human carcinogen that has been classified as a priority water pollutant by the European Commission, have been quickly degraded and even totally mineralized by different electrochemical advanced oxidation processes (EAOPs) in cells equipped with a carbonaceous air-diffusion cathode able to electrogenerate H2O2 on site and a Pt or boron-doped diamond (BDD) anode. The highest performance was obtained by means of the photoelectro-Fenton (PEF) process with BDD in the presence of 0.5mM Fe2+, thanks to the synergistic action of (i) electron transfer, (ii) coupled oxidation by OH generated by Fenton’s reaction in the solution bulk and BDD(OH) generated at the anode surface, and (iii) photolytic and photodecarboxylation reactions allowed by UVA photons. Good results were also obtained by electro-oxidation (EO) and electro-Fenton (EF) with BDD, resulting in a much higher mineralization current efficiency than EO, EF and PEF with Pt. Based on GC–MS analyses, the initial transformation step of alachlor promoted by the EAOPs involved four different reaction pathways, namely dealkylation, cyclization, scission of the R–N bond and hydroxylation by OH and BDD(OH). Further cleavage of the resulting nine cyclic and/or aromatic by-products led to the appearance of short-chain aliphatic carboxylic acids such as acetic, chloroacetic, oxamic and oxalic. Only PEF with BDD was able to ensure the quick and total degradation of the latter two acids, therefore becoming the best available electrochemical technology at present for the degradation of alachlor. Different amounts of nitrogenated (NH4+ and NO3−) and chlorinated (Cl−, ClO3− and ClO4−) ions were accumulated in the final solutions depending on the anode and the applied current.

Degradation of anti-inflammatory drug ketoprofen by electro-oxidation: comparison of electro-Fenton and anodic oxidation processes.

The electrochemical degradation of the nonsteroidal anti-inflammatory drug ketoprofen in tap water has been studied using electro-Fenton (EF) and anodic oxidation (AO) processes with platinium (Pt) and boron-doped diamond (BDD) anodes and carbon felt cathode. Fast degradation of the parent drug molecule and its degradation intermediates leading to complete mineralization was achieved by BDD/carbon felt, Pt/carbon felt, and AO with BDD anode. The obtained results showed that oxidative degradation rate of ketoprofen and mineralization of its aqueous solution increased by increasing applied current. Degradation kinetics fitted well to a pseudo-first-order reaction. Absolute rate constant of the oxidation of ketoprofen by electrochemically generated hydroxyl radicals was determined to be (2.8 ± 0.1) × 10(9) M(-1) s(-1) by using competition kinetic method. Several reaction intermediates such as 3-hydroxybenzoic acid, pyrogallol, catechol, benzophenone, benzoic acid, and hydroquinone were identified by high-performance liquid chromatography (HPLC) analyses. The formation, identification, and evolution of short-chain aliphatic carboxylic acids like formic, acetic, oxalic, glycolic, and glyoxylic acids were monitored with ion exclusion chromatography. Based on the identified aromatic/cyclic intermediates and carboxylic acids as end products before mineralization, a plausible mineralization pathway was proposed. The evolution of the toxicity during treatments was also monitored using Microtox method, showing a faster detoxification with higher applied current values.

Screening and determination of aliphatic organic acids in commercial Brazilian sugarcane spirits employing a new method involving capillary electrophoresis and a semi-permanent adsorbed polymer coating

A simple method for the screening and determination of short chain aliphatic carboxylic acids in Brazilian sugarcane spirits by indirect capillary zone electrophoresis was developed and validated according to Eurachem guidelines. The separations were performed in a coated capillary (Ltot 73cm×Ldet 64.5cm) with 2-hydroxy-propyltrimethyl-ammonium chloride chitosan. The background electrolyte was optimized using Peakmaster® software and was composed of 21mmolL−1 β-alanine and 10mmolL−1 3,5 dinitrobenzoic acid, at pH3.6, with an applied voltage of −30kV. The method was validated for formic, lactic and acetic acids. Linearity was demonstrated and significant matrix effects were not observed at between 2.8 and 144mgL−1. The recovery (means of 89.6–117.9%) was evaluated, and ANOVA was carried out to determine the RSD values for the repeatability (2.63–8.35%) and reproducibility (1.92–6.62%). The LOD and LOQ ranged from 0.69 to 2.70 and 2.76 to 8.11mgL−1, respectively. The concentrations detected in the samples were 0.19–106.43mg per 100g.

Generating power from cellulose in an alkaline fuel cell enhanced by methyl viologen as an electron-transfer catalyst

In this work, we developed a single-compartment direct cellulose alkaline fuel cell by using nickel foam as the anode and methyl viologen as an electron transfer catalyst. The maximum power density of the fuel cell at optimal conditions is 450 mW m−2. High-performance liquid chromatography detected short-chain aliphatic carboxylic acids in the oxidation products. Using common reed and red algae as fuels, the fuel cell achieved maximum power densities of 295 mW m−2 and 154 mW m−2, respectively.

Dissolved organic matter: Fractional composition and sorbability by the soil solid phase (Review of literature)

The behavior of dissolved organic matter (DOM) in soils under varying environmental conditions represents a poorly studied aspect of the problem of organic matter loss from soils. The equilibrium and sustainable development of ecosystems in the northern latitudes are largely determined by the balance between the formation of DOM, its accumulation in the lower soil horizons, and its input with runoff into surface waters. The residence time, retention strength in the soil, and thermodynamic and biochemical stabilities depend on the localization of DOM in the pore space and its chemical structure. Amphiphilic properties represent a valuable diagnostic parameter, which can be used to predict the behavior of DOM in the soil. Acidic components of hydrophobic and hydrophilic nature constitute the major portion of DOM in forest soils of the temperate zone. The hydrophilic fraction includes short-chain aliphatic carboxylic acids, hydrocarbons, and amino acids and is poorly sorbed by the solid phase. However, the existence of this fraction in soil solution is also limited both in space (in the finest pores) and time because of higher accessibility to microbial degradation. The hydrophilic fraction composes the major portion of labile DOM in soils. The hydrophobic fraction consists of soluble degradation products of lignin; it is enriched in structural ortho-hydroxybenzene fragments, which ensure its selective sorption and strong retention in soils. Sorption is favored by low pH values (3.5–5), the high ionic strength of solution, the heavy texture and fine porous structure of soil, the high contents of oxalate- and dithionite-soluble iron (and aluminum) compounds, and hydrological conditions characterized by slow water movement. The adsorbed DOM is chemically and biochemically recalcitrant and significantly contributes to the humus reserves in the low mineral horizons of soils.

Application of flow-injection potentiometric system for determination of total concentration of aliphatic carboxylic acids

In this work, flow-injection system with potentiometric detection was tested for determination of total carboxylic acid concentration. Detection part of the examined system consists of ion-selective electrodes (ISEs) with polymer membranes of different compositions. First electrode is based on Zr(IV)-tetraphenylporphyrin as ionophore selective towards carboxylic acid anions, the membrane of second one contains only liphophilic anion exchanger – tridodecylmethylammonium chloride. Final response of the system is a result of combination of EMF signals from both electrodes. Combination of two detectors enables significant decrease of differences between potentiometric signals induced by mixtures of studied anions of various concentrations as compared to results obtained only with metalloporphyrin-based ISE. The use of anion-exchanger based detector allows for elimination of the influence of aliphatic carboxylic acids lipophilicity.Proposed potentiometric flow-injection system was employed for determination of short-chain aliphatic carboxylic acids (so-called VFA – volatile fatty acids) in samples originating from an anaerobic digester. Results obtained for these relatively complicated samples are in good agreement with results obtained with the use of reference colorimetric method.Linear response towards carboxylic acids was observed in the concentration range of 10−4 to 10−2moldm−3, with the slopes in the range of −110 to −150mVdec−1 (for acetate− and butyrate−, respectively). System enables for determination of about 6 samples per hour. Life time of ISEs average about 2 months.

Electron Beam Radiolysis of Diethyl Phthalate in Aqueous Solutions

Abstract Electron beam radiolysis experiments were undertaken to gain insights into the kinetic mechanisms of diethyl phthalate (DEP) degradation in aqueous solutions. DEP degradation was found to follow pseudo-first-order kinetics. The pseudo-first-order rate constant decayed exponentially with DEP initial concentrations (C0), whereas G values of DEP and C0 followed linear relationship. Addition of sodium carbonate to irradiated DEP solutions reduced DEP decomposition. H2O2 was not favorable for removal of DEP. An effective degradation was achieved in both N2O-saturated and t-BuOH–containing N2-saturated DEP solutions. High removals (>99%) were achieved at 15 kGy without these radical scavengers. Radical scavenging tests indicated that both •OH and e−aq played significant roles in DEP radiolysis. Several intermediates such as monoethyl phthalate, phthalate acid, and short-chain aliphatic carboxylic acids were formed from DEP radiolytic degradation. Finally, DEP was completely mineralized when the absorbe...