The Influence of Water Activity on Double Layer Parameters on the Interface Mercury/Chlorates (VII) in the Presence of Cysteine

The influence both the cysteine concentration and water activity on the double layer parameters on the interface mercury/ chlorates (VII) was examined. The adsorption parameters for the double layer were calculated from a double-layer differential capacity measurement extrapolated to zero frequency. The values of the relative surface excess increase of the cysteine concentration and chlorates (VII) solutions. It was found that the values of free adsorption energy and interactions constants, obtained from Frumkin and virial isotherms, depend on the supporting electrolyte concentration. The changes of determined parameters in the function of water activity water point at the participation of 4 ClO ions in the adsorption processes, or that in the double layer the electrostatic interactions between the dipoles of 2 H O and cysteine compounds exist.(doi: 10.5562/cca2022

The Influence of Protonation on the Electroreduction of Bi (III) Ions in Chlorates (VII) Solutions of Different Water Activity

We examined the electroreduction of Bi (III) ions in chlorate (VII) solutions under varied protonation conditions of the depolariser using voltammetric and impedance methods. The results of the kinetic parameter correlation lead to the statement that the changes in the amount of chloric (VII) acid against the amount of its sodium salt in the supporting electrolytes of the low water activity have a significant influence on the rate of Bi (III) ion electroreduction. The increase of the concentration of chloric acid sodium salt, aswell as the chloric (VII) acid alone within the particular concentration of the supporting electrolyte, inhibits the process of Bi (III) ion electroreduction. It should be associated with the reorganisation of the structure of the double layer connected with the slow dehydration inhibited by ClO 4 − ions. The standard rate constants ks values with the increase of the chlorate (VII) concentrations for all the solutions examined of chlorates (VII) confirms the catalytic influence of the decrease of water activity on the process of Bi (III) ion electroreduction. The multistage process is confirmed by the non-rectilinear 1nkf=f(E) dependences

Elektrochemická studie flumetralinu pomocí cyklicky obnovitelné filmové elektrody ze stříbrné amalgámy

The electrochemical properties of flumetralin (FLM) were investigated using square wave stripping voltammetry (SWSV) at cyclic renewable silver amalgam film electrode (Hg(Ag)FE). Two cathodic signals of FLM were recorded at Hg(Ag)FE in Britton-Robinson buffer of pH 9.5. After optimization of SWSV parameters and pH of supporting electrolyte, the linearity of peak currents vs. concentrations of FLM was found in the range of 5×10-9 mol L-1 - 1×10-7 mol L-1 with a detection limit 6.43×10-10 mol L-1. The developed method has been applied for the quantitative analysis of FLM in spiked tap water.Elektrochemické vlastnosti flumetralinu (FLM) byly studovány pomocí square wave anodické rozpouštěcí voltametrie (SWSV) na cyklicky obnovitelné filmové elektrodě ze stříbrné amalgámy (Hg(Ag)FE). Byly zaznamenány dva katodické signály FLM v Brittonově-Robinsonově pufru o pH 9,5. Po optimalizaci parametrů SWSV a pH základního elektrolytu byl zjištěn lineární rozsah závislosti proudu píku na koncentraci FLM v rozmezí 5×10-9 mol L-1 - 1×10-7 mol L-1 s detekčním limitem stanovení 6.43×10-10 mol L-1. Navržená metoda byla použita pro kvantitativní analýzu FLM ve vzorku vody

Study of 2–thiocytosine/ surfactant adsorption at the R-AgLAFe/chlorate(VII) interface – impact of surfactant ionic character

Effect of 2 – thiocytosine on the parameters of double R-AgLAFe/ chlorate(VII) interface layer in the presence of different surfactants has been studied. There were determined the adsorption parameters such as: differential capacity of the double layer (Cd) at the R-AgLAFe/ basic electrolyte interface; potential of zero charge (Ez) and surface tension at the potential of zero charge (γz). The predominance of 2–thiocytosine in formation of adsorption equilibria of 2–thiocytosine–SDS and 2– thiocytosine–CTAB mixtures as well as the competitive adsorption between molecules 2–thiocytosine-surfactant or mixed micelles was proved. The changes pointing out to different arrangement of SDS or CTAB molecules on the electrode surface also in the presence of 2–thiocytosine were observed

Electroreduction of Bi(III) Ions at a Cyclically Renewable Liquid Silver Amalgam Film Electrode in the Presence of Methionine

The catalytic influence of methionine (Mt) on the electroreduction of Bi(III) ions on the novel, cyclically renewable liquid silver amalgam film electrode (R–AgLAFE) in a non-complexing electrolyte solution was examined. The presence of methionine leads to a multistep reaction mechanism, where the transfer of the first electron is the rate limiting step, which is the subject of catalytic augmentation. The catalytic activity of methionine is a consequence of its ability to remove water molecules from the bismuth ion coordination sphere, as well as to form active complexes on the electrode surface, facilitating the electron transfer process

Microporous Biocarbons Derived from <i>Inonotus obliquus</i> Mushroom and Their Application in the Removal of Liquid and Gaseous Impurities

Biocarbons were obtained by physical and chemical activation of the residue of the extraction of chaga fungi (Inonotus obliquus). The residue was subjected to heat treatment carried out in a microwave oven and in a quartz tubular reactor. The materials were characterized by elemental analysis, low-temperature nitrogen adsorption, determination of pH, and the contents of acidic and basic oxygen functional groups on the surface of biocarbons by the Boehm method. The final biocarbon adsorbents have surface areas varying from 521–1004 m2/g. The physical activation of the precursor led to a strongly basic character of the surface. Chemical activation of Inonotus obliquus promoted the generation of acid functional groups. All biocarbons were used for methyl red sodium salt adsorption from the liquid phase. The sorption capacities of biocarbons towards the organic dye studied varied from 77 to 158 mg/g. The Langmuir model was found to better describe the experimental results. The results of the kinetic analysis showed that the adsorption of methyl red sodium salt on the biocarbons followed the pseudo-second-order model. The acidic environment was conducive to the adsorption of the dye on the obtained biocarbons. Moreover, thermodynamic studies confirmed that the organic dye adsorption on the biocarbons was a spontaneous endothermic process. The biocarbons obtained were also tested as adsorbents of hydrogen sulfide in dry and wet conditions. The sorption capacities towards hydrogen sulfide varied in the range of 21.9–77.9 mg. The results have shown that the adsorption of hydrogen sulfide depends on the process conditions and the activation procedure of biocarbons (method of activation and thermochemical treatment of samples). It has been shown that the initial material used can be a new precursor for obtaining cheap and—more importantly—universal bioadsorbents characterized by high effectiveness in the removal of air and water pollutants

First Electrochemical Method of Nitrothal-Isopropyl Determination in Water Samples

The aim of the research was the use of square wave adsorptive stripping voltammetry (SWAdSV) in conjunction with a hanging mercury drop electrode (HMDE) for the determination of nitrothal-isopropyl. It was found that optimal SW technique parameters were frequency, 200 Hz; amplitude, 50 mV; and step potential, 5 mV. Accumulation time and potential were studied to select the optimal conditions in adsorptive stripping voltammetry: 45 s at 0.0 V, respectively. The calibration curve (SWSV) was linear in the nitrothal-isopropyl concentration range from 2.0 × 10−7 to 2.0 × 10−6 mol L−1 with detection limit of 3.46 × 10−8 mol L−1. The repeatability of the method was determined at a nitrothal-isopropyl concentration level equal to 6.0 × 10−7 mol L−1 and expressed as RSD = 5.5% (n=6). The proposed method was successfully validated by studying the recovery of nitrothal-isopropyl in spiked environmental samples