Kinetic regularities of electrochemical oxidation of the methionine anion on platinated platinum

The purpose of this study was the determination of the kinetic regularities of the methionine electrooxidation process on the Pt(Pt) electrode in an aqueous-alkaline medium.The main kinetic regularities of the methionine anion electrooxidation process were determined using by the methods of cyclic voltammetry, coulometry, and electrochemical impedance spectroscopy. The concentration of methionine in the alkaline solution before and after anodic oxidation was determined spectrophotometrically using spectrophotometer UNICO 2800. The measurements were carried out at room temperature both in an argon atmosphere and in an aerated aqueous solution. The results of voltammetric measurements were adjusted for the limiting oxygen recovery current and the charging current of the double electric layer.The range of potentials of the electrochemical activity of the methionine anion on the Pt(Pt) electrode, the number of electrons involved in the anode process, and its kinetic scheme were determined. The main product of the electrooxidation of methionine in an alkaline medium on Pt(Pt) was the methionine sulfoxide anion. It was shown that the electrooxidation of the methionine anion on Pt (Pt) was carried out from the adsorbed state and was irreversible.

Modeling the Electronic Properties for CNT Interacted with ZnO, CuO and Co3O4

Because of the wide applications of carbon nanotubes (CNTs) and magic properties of metal oxides, Hartree-Fock (HF)/STO-3G quantum mechanical calculations were applied to study the electronic properties of CNTs and its interaction with ZnO, CuO and Co3O4. Calculations were conducted to calculate HOMO/LUMO band gap energy ∆E, moleculare electrostatic potential (MESP) and total dipole moment (TDM) for CNTs, CNT-Zn-O, CNT-Cu-O, CNT-Co-O and CNT-O-Zn, CNT-O-Cu, CNT-O-Co following the two mechanism of interaction as adsorbed and complex state. The calculations show that the interaction of CNTs with metal oxides increases its reactivity where MESP indicated to more distribution charges and an increasing in the TDM value after interaction of CNTs with metal oxides. Where, the interaction of CNT-Co-O as adsorbed state has the highest TDM with lowest band gap ∆E which confirms that CNT-Co3O4 can be used in sensing devices.

Hydrogen sulfide occurrence states in China's coal seams

The occurrence states of hydrogen sulfide in coal seams are crucial in preventing and controlling hydrogen sulfide emission in coal mines and the safe development of coal bed methane. In this study, the research status of the occurrence states of free-state, adsorbed-state, and water-soluble hydrogen sulfide in coal seams was systematically analyzed. H2S anomaly areas in China's coal seams are mainly located in the Carboniferous-Permian and Jurassic series of northern, eastern, central, and northwest regions of China. Bacterial sulfate reduction accounts for most of the hydrogen sulfide anomalies of low-rank coal, while thermochemical decomposition thermal desorption spectroscopy and thermochemical sulfate reduction may also result in hydrogen sulfide anomaly in medium- and high-rank coal. In contrast, magmatism-induced hydrogen sulfide anomalies are rarely found. Absorbed-state hydrogen sulfide anomalies are prevailing, while water-soluble and free-state hydrogen sulfide anomalies are relatively scarce. Coal seam's porosity mainly controls the hydrogen sulfide adsorption, pressure, coalification degree, pore volume, and specific area, while water-soluble hydrogen sulfide is influenced by pressure, sulfate-reducing bacteria, burn, porosity, fractures, water temperature, and hydrodynamic conditions. The fractures in coal seams, their burial depth, coal quality, coal rank, roof, and floor lithology are the main factors controlling the free-state hydrogen sulfide preservation. The absorbed-state hydrogen sulfide in coal seams is mainly mitigated by varying the ventilation mode, increasing the ventilation capacity, spraying alkali fog into the air, and injecting alkali liquid into coal seams for governance.

Thermodynamic Impact of Mineral Surfaces on Amino Acid Polymerization: Aspartate Dimerization on Two-Line Ferrihydrite, Anatase, and γ-Alumina

The presence of amino acids in diverse extraterrestrial materials has suggested that amino acids are widespread in our solar system, serving as a common class of components for the chemical evolution of life. However, there are a limited number of parameters available for modeling amino acid polymerization at mineral–water interfaces, although the interfacial conditions inevitably exist on astronomical bodies with surface liquid water. Here, we present a set of extended triple-layer model parameters for aspartate (Asp) and aspartyl-aspartate (AspAsp) adsorptions on two-line ferrihydrite, anatase, and γ-alumina determined based on the experimental adsorption data. By combining the parameters with the reported thermodynamic constants for amino acid polymerization in water, we computationally demonstrate how these minerals impact the AspAsp/Asp equilibrium over a wide range of environmental conditions. It was predicted, for example, that two-line ferrihydrite strongly promotes Asp dimerization, leading to the AspAsp/Asp ratio in the adsorbed state up to 41% even from a low Asp concentration (0.1 mM) at pH 4, which is approximately 5 × 107 times higher than that attainable without mineral (8.5 × 10−6%). Our exemplified approach enables us to screen wide environmental settings for abiotic peptide synthesis from a thermodynamic perspective, thereby narrowing down the geochemical situations to be explored for life’s origin on Earth and Earth-like habitable bodies.

Redundancy-Free Models for Mathematical Descriptions of Three-Phase Catalytic Hydrogenation of Cinnamaldehyde

A new approach on how to formulate redundancy-free models for mathematical descriptions of three-phase catalytic hydrogenation of cinnamaldehyde is presented. An automatically created redundant (generalized) model is formulated according to the complete reaction network. Models based on formal kinetics and kinetics concerning the Langmuir-Hinshelwood theory for three-phase catalytic hydrogenation of cinnamaldehyde were investigated. Redundancy-free models were obtained as a result of a step-by-step elimination of model parameters using sensitivity and interval analysis. Starting with 24 parameters in the redundant model, the redundancy-free model based on the Langmuir-Hinshelwood mechanism contains 6 parameters, while the model based on formal kinetics includes only 4 parameters. Due to less degrees of freedom of molecular rotation in the adsorbed state, the probability of a direct conversion of cinnamaldehyde to 3-phenylpropanol according to the redundancy-free model based on Langmuir-Hinshelwood approach is practically negligible compared to the model based on formal kinetics.

Thermodynamic Impact of Mineral Surfaces on Amino Acid Polymerization: Aspartate Dimerization on Ferrihydrite, Anatase and γ-alumina

The ubiquity of amino acids in carbonaceous meteorites has suggested that amino acids are widespread in the Universe, serving as a common class of components for the emergence of life. However, parameters for modeling amino acid polymerization at mineral–water interfaces remain limited, although the interfacial conditions inevitably exist on planets with surface liquid water. Here, we present a set of extended triple-layer model parameters for aspartate (Asp) and aspartyl-aspartate (AspAsp) adsorptions on ferrihydrite, anatase, and γ-alumina determined based on the experimental adsorption data. By combining the parameters with the reported thermodynamic constants for amino acid polymerization in water, the impacts of these minerals on Asp dimerization are calculable over a wide range of environmental conditions. It was predicted, for example, that ferrihydrite strongly increases the AspAsp/Asp equilibrium ratio in neutral to acidic pH; the ratio in the adsorbed state reaches 40% even from a low Asp concentration (0.1 mM) at pH 4. This percentage is approximately 5 × 107 times higher than that attainable without mineral (8.5 × 10–6%). Our exemplified approach enables us to screen wide environmental settings for abiotic peptide synthesis from a thermodynamic perspective, thereby narrowing down the geochemical situations to be explored for life’s origin on Earth and Earth-like habitable planets.

A novel catalytic adsorptive stripping voltammetric method for the determination of germanium ultratraces in the presence of chloranilic acid and the V(IV)·HEDTA complex

A novel, sensitive catalytic adsorptive stripping voltammetric procedure which can be used to determine trace amounts of germanium is described. The method is based on the interfacial accumulation of the complex formed by Ge(IV) and the product of the reduction of chloranilic acid on the hanging mercury drop electrode or the renewable silver amalgam film electrode, and its subsequent reduction from the adsorbed state followed by the catalytic action of the V(IV)·HEDTA complex. The presence of V(IV)·HEDTA greatly enhances the adsorptive stripping response of Ge. The reduction of the Ge(IV) in the presence of chloranilic acid and V(IV)·HEDTA was investigated in detail and the effects of pH, electrolyte composition, and instrumental parameters were studied. Under optimal conditions, the catalytic peak current of germanium exhibited good linearity for Ge(IV) concentrations in the range of 0.75–60 nM (for 60 s of accumulation at −0.1 V, r2 = 0.995) and a low limit of detection (LOD = 0.085 nM). The procedure was successfully applied to determine Ge in water samples.

Enhanced magnetorheological effect and sedimentation stability of bimodal magnetorheological fluids doped with iron nanoparticles

The improvement of properties of magnetorheological fluids and mechanism study has long been a classic area within the field of magnetorheological materials. This article was undertaken to dope the iron nanoparticles synthesized by direct current electric arc discharge with the traditional carbonyl iron powders to prepare bimodal magnetorheological fluids with different doping ratios. Their rheological properties and sedimentation stability were evaluated to explore the influence rules and mechanisms. The results indicate that the effect of the addition of iron nanoparticles on rheological properties under magnetic field is a combination of two opposing factors such as the strengthening of the structure and the weakening of magnetization. The sedimentation stability of the bimodal magnetorheological fluids improved significantly with the increase in the proportion of iron nanoparticles, which is attributed to the help of both free state and adsorbed state iron nanoparticles in magnetorheological fluids. Furthermore, within a specific magnetic field strength range, the bimodal magnetorheological fluids with a small proportion of iron nanoparticles can achieve an improvement in both rheological property and sedimentation stability compared with carbonyl iron particles–based magnetorheological fluids.

Behavior of PBTC, HEDP, and Aminophosphonates in the Process of Wastewater Treatment

Ten times at intervals of 1–2 months, individual treatment stages of two wastewater treatment plants (WWTPs) were analyzed for the five quantitatively most widely used phosphonates. The total dissolved concentration of the investigated phosphonates in the influents was between 131 µg/L and 384 µg/L. The nitrogen-free phosphonates 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC) and 1-hydroxyethylidene(1,1-diphosphonic acid) (HEDP) accounted for an average proportion of 83–85%. Diethylenetriaminepenta(methylene phosphonic acid) (DTPMP) contributed with 13–14%, whereas aminotris(methylphosphonic acid) (ATMP) (≤15 µg/L) and ethylenediaminetetra(methylene phosphonic acid) (EDTMP) (≤11 µg/L) contents detected in the WWTP influents were comparatively low. The application of new analytical methods allowed the quantification of phosphonates in the solid fraction of the WWTP influents for the first time. High loads of phosphonates were determined (223–2555 mg/kg), indicating that 20%–80% of the phosphonates are present in the adsorbed state. The removal of total dissolved phosphonate by secondary clarification was between 69.7% and 92.4% (medians: 90.7% and 87.7%). In both WWTPs, HEDP (medians: 89.2% and 86.4%) was slightly better eliminated than PBTC (medians: 87.2% and 82.5%). In the sand filtration stage of a WWTP, the average removal was not further improved. In contrast, an additional removal of dissolved phosphonates could be achieved by activated carbon treatment (median: 96.4%). The proportion of phosphonate-P in the dissolved unreactive phosphorus fraction was consistently between 10% and 40% throughout all treatment stages.