Electrochemical Generation of Superoxide in Room-Temperature Ionic Liquids

We have demonstrated that superoxide ion can be generated electrochemically in room-temperature ionic-liquid solvents. In the absence of impurities, cyclic voltammetry showed that the super oxide ion is stable in these solvents. Similar superoxide ion chemistry has previously been demonstrated in volatile and environmentally suspect aprotic solvents such as dimethyl formamide and acetonitrile. However, ionic liquids are nonvolatile and should minimize the problems of secondary solvent waste. It is proposed that the resultant superoxide ion can be used to perform low temperature oxidation of wastes. Low-temperature oxidation of waste solvents can provide a much needed alternative to high-temperature waste incinerators, whose use is greatly complicated by regulatory requirements and locating suitable sites

Utilizing ultrasonic energy for reduction of free fatty acids in crude palm oil

Recently, biodiesel production from abundant bio-sources has drawn the attention of the academic and the industrial community. In this study, crude palm oil (CPO) containing 8.7% free fatty acid content (FFA) was used as raw material. Different common types of acid catalysts (sulfuric acid, methanesulfonic acid and hydrochloric acid) were optimized to investigate the catalytic activity of each acid in the pre-treatment of CPO by the esterification process. Ultrasonic energy was used for the reduction of FFA in CPO. FFA content was measured at different sonication intervals, and the optimum time was determined. Hydrochloric acid showed the highest catalytic activity in the reduction of FFA content in CPO, as well as in converting FFA to fatty acid methyl ester (FAME). From this work, it is reasonable to conclude that there is significant enhancement in the pre-treatment of oils by applying ultrasonic energy using long sonication time.Keywords: Biodiesel, crude palm oil, free fatty acids, ultrasonic energ

Temperature Effects on the Kinetics of Ferrocene and Cobaltocenium in Methyltriphenylphosphonium Bromide Based Deep Eutectic Solvents

The oxidation of ferrocene (Fc/Fc+) and reduction of cobaltocenium (Cc+/Cc) under different temperatures has been studied by cyclic voltammetry and double potential step chronoamperometry in deep eutectic solvents (DESs) consisting of methyltriphenylphosphonium bromide salt with tri-ethylene glycol, glycerol or ethylene glycol as hydrogen bond donors. The temperature dependence of the measured physical properties of DESs (such as viscosity and conductivity) is discussed in detail. The kinetics of the redox couples are studied using cyclic voltammetry, and the standard heterogeneous electron transfer rate constant, k0 is found to be of the order of 10−5 to 10−4 cms−1 at different temperatures. The diffusion coefficient, D, of Fc and Cc+ is determined to lie between 8.28 × 10−10 to 6.65 × 10−9 cm2 s−1. These results show that both k0 and D increase with temperature in the studied DESs. In addition, better kinetic parameters for the DES with ethylene glycol as hydrogen bond donor means that this could be evaluated favorably as both solvents and electrolytes for redox flow cells

A humid electronic nose based on pulse voltammetry: A proof-of-concept design

[EN] We report herein the design, manufacture and use of a "humid electronic nose" prototype based on voltammetric techniques. It consists of an array of four working electrodes (i.e., Au, Pt, Ir and Rh) housed inside a homemade stainless steel cylinder, in contact with a fabric mesh made of nylon damped with a NaCl aqueous solution, used as the supporting humid membrane. The "humid electronic nose" was tested for the discrimination of different samples displaying different volatile compounds. The samples chosen involve aqueous solutions of different simple volatile products (i.e., ammonia, acetone, acetic acid and 6-amino-1-hexanol) and different food samples (i.e., onion, coffee and Roquefort cheese). Under working conditions, the volatile compounds from the corresponding sample were generated in the measurement chamber and were partially dissolved in the damped nylon fabric, which was in contact with the set of electrodes. It was envisioned that provided different samples offer different vapours, the application of a suitable set of pulses to the electrodes will differentiate the samples. This proof-of-concept study employed a Large Amplitude Pulse Voltammetry (LAPV) waveform. The increment for the potential steps was of 200 mV and potentials ranged from +1 to -1 V with each pulse applied for 50 ms. PCA studies from the response obtained by the "humid electronic nose" discriminated the different samples studied. The neural network Self Organized Map (SOM) was also used to analyze the electrochemical data obtained from the "humid electronic nose". © 2013 Elsevier B.VThe financial support from the Spanish Government (project MAT2012-38429-C04) and the Generalitat Valenciana (Valencian Regional Government; projects PROMETEO/2009/016 and GV/2012/094); is gratefully acknowledged.Bataller Prats, R.; Campos Sánchez, I.; Alcañiz Fillol, M.; Gil Sánchez, L.; García Breijo, E.; Martínez Mañez, R.; Pascual Vidal, L.... (2013). A humid electronic nose based on pulse voltammetry: A proof-of-concept design. Sensors and Actuators B: Chemical. 186:666-673. https://doi.org/10.1016/j.snb.2013.06.033S66667318

Investigation of ammonium- and phosphonium-based deep eutectic solvents as electrolytes for a non-aqueous all-vanadium redox cell

The charge/discharge characteristics for vanadium acetylacetonate in deep eutectic solvents were evaluated using an H-cell with an anion-exchange membrane separator for the first time. Coulombic (CE) and energy efficiencies (EE) of the electrolyte containing V(acac)3/0.5 M TEABF4 in DES3 (a hydrogen bonded eutectic between choline chloride and ethylene glycol) were obtained as 49-52% and 25-31%, respectively, when charging from 0 to 50% of theoretical maximum state-of-charge for 12 cycles. The low CE may be due to the crossover of the active species through the separator, or to the loss of active vanadium due to a parasitic reaction. However, the CE was similar to that for acetonitrile (CH3CN) indicating the promise of DESs as suitable electrolytes for future evaluation. Charge and discharge voltages are respectively higher and lower than the formal cell potential obtained by voltammetry. Ohmic drop in the DES results from the low conductivity of the electrolyte and the relatively large distance between the two electrodes in the H-cell. Further studies require investigation in a flow cell with analyses of polarization curves and impedance to determine the loss mechanisms in sufficient detail

Preparation of sustainable activated carbon-alginate beads impregnated with ionic liquid for phenol decontamination

Powder activated carbon (PAC), derived from calligonum pollygonides, was successfully modified with the ionic liquid (IL) trihexyltetradecylphosphonium bromide ([PC6C6C6C14][Br]) in the presence of sodium alginate and characterized using SEM, FTIR and TGA. PAC, granular AC (GAC), AC-alginate and AC-Alg-IL bead were assessed for the removal of phenol from aqueous media via batch adsorption. Both PAC and AC-Alg-IL beads displayed high adsorption capacities, 123 mg/g and 78 mg/g, respectively, under optimized conditions. In contrast, GAC gave a much lower adsorption capacity than AC-ALG-IL beads, indicating that AC-ALG-IL beads are superior as potential adsorbents for this industrial application. Theoretical studies showed that the pseudo-second-order kinetic and Freundlich isotherm models were suitable to describe the adsorption process. The interaction between phenol and AC-Alg-IL beads was analyzed using the conductor-like screening model for realistic solvents (COSMO-RS). It has been concluded that AC-Alg-IL beads can be used as an efficient adsorbent for phenol and other organic compounds

The effect of temperature on kinetics and diffusion coefficients of metallocene derivatives in polyol-based deep eutectic solvents

The temperature dependence of the density, dynamic viscosity and ionic conductivity of several deep eutectic solvents (DESs) containing ammonium-based salts and hydrogen bond donvnors (polyol type) are investigated. The temperature-dependent electrolyte viscosity as a function of molar conductivity is correlated by means of Walden's rule. The oxidation of ferrocene (Fc/Fc+) and reduction of cobaltocenium (Cc+/Cc) at different temperatures are studied by cyclic voltammetry and potential-step chronoamperometry in DESs. For most DESs, chronoamperometric transients are demonstrated to fit an Arrhenius-type relation to give activation energies for the diffusion of redox couples at different temperatures. The temperature dependence of the measured conductivities of DES1 and DES2 are better correlated with the Vogel-Tamman-Fulcher equation. The kinetics of the Fc/Fc+ and Cc+/Cc electrochemical systems have been investigated over a temperature range from 298 to 338 K. The heterogeneous electron transfer rate constant is then calculated at different temperatures by means of a logarithmic analysis. The glycerol-based DES (DES5) appears suitable for further testing in electrochemical energy storage devices

Kinetics of superoxide ion in dimethyl sulfoxide containing ionic liquids

The chemical generation of superoxide ion (O-2 (aEuro cent a')) by dissolving potassium superoxide was investigated. The chemically generated O-2 (aEuro cent a') was then used to study the long-term stability of O-2 (aEuro cent a') in dimethyl sulfoxide (DMSO) containing ionic liquids (ILs) and determine the rate constants based on pseudo 1st- and 2nd-order reactions between the IL and O-2 (aEuro cent a') generated in DMSO. O-2 (aEuro cent a') was unstable in DMSO containing S-222TFSI, DMImMS, BDMImTfO, EMImTFSI, EMImMS, P-14,P-666TPTP, P-14,P-666TFSI, and all pyridinium-based ILs. In contrast, O-2 (aEuro cent a') was very stable in DMSO containing MOPMPipTFSI, BMPyrrDCA, BMPyrrTFSI, BMPyrrTfO, HMPyrrTFSI, MOEMPipTPTP, BMPyrrTFA, N-112,1O(2)TFSI, and MOEMMorTFSI. This shows that these ILs can be used for different applications involving O-2 (aEuro cent a'). The reaction rate constant, total consumption, and consumption rate of O-2 (aEuro cent a') were determined. The rate constants of O-2 (aEuro cent a') in some ILs were found to follow pseudo 1st-order reaction, while in others, pseudo 2nd-order reaction kinetics were observed

COSMO-RS Prediction for Choline Chloride/Urea Based Deep Eutectic Solvent: Chemical Structure and Application as Agent for Natural Gas Dehydration

In recent years, green solvents named deep eutectic solvents (DESs) have been found to possess significant properties and to be applicable in several technologies. Choline chloride (ChCl) mixed with urea at a ratio of 1:2 and 80 °C was the first discovered DES. In this article, chemical structure and combination mechanism of ChCl: urea based DES were investigated. Moreover, the implementation of this DES in water removal from natural gas was reported. Dehydration of natural gas by ChCl:urea shows significant absorption efficiency compared to triethylene glycol. All above operations were retrieved from COSMOthermX software. This article confirms the potential application of DESs in gas industry

A novel technique for separating glycerine from palm oil-based biodiesel using ionic liquids

Biodiesel production from abundant bio-sources has drawn the attention of the academic as well as the industrial communities in recent years. However, one of the most serious obstacles for using biodiesel as an alternative fuel is the complicated and costly purification processes involved in its production. The difficulties involved in the separation of glycerine and other un-reacted reactants and by-products necessitate the development of new competent low cost separation processes for this purpose. In this work, a low cost quaternary ammonium salt-glycerine-based ionic liquid is proposed as a solvent for extracting glycerine from the transesterification biodiesel product. The separation technique was tested on palm oil-based produced biodiesel with KOH as a reaction catalyst. The study investigated the effect of DES:biodiesel ratio and the DES composition on the efficiency of the extraction process. The lab scale purification experiments proved the viability of the separation technique with a best DES:biodiesel molar ratio of 1:1 and a DES molar composition of 1:1 (salt:glycerine). The purified biodiesel fulfilled the EN 14214 and ASTM D 6751 standard specifications for biodiesel fuel in terms of glycerine content. A continuous separation process is suggested for industrial scale application. © 2009 Elsevier B.V. All rights reserve