A Sensitive Micro Conductometric Ethanol Sensor Based on an Alcohol Dehydrogenase-Gold Nanoparticle Chitosan Composite

In this paper, a microconductometric sensor has been designed, based on a chitosan composite including alcohol dehydrogenase—and its cofactor—and gold nanoparticles, and was calibrated by differential measurements in the headspace of aqueous solutions of ethanol. The role of gold nanoparticles (GNPs) was crucial in improving the analytical performance of the ethanol sensor in terms of response time, sensitivity, selectivity, and reproducibility. The response time was reduced to 10 s, compared to 21 s without GNPs. The sensitivity was 416 µS/cm (v/v%)−1 which is 11.3 times higher than without GNPs. The selectivity factor versus methanol was 8.3, three times higher than without GNPs. The relative standard deviation (RSD) obtained with the same sensor was 2%, whereas it was found to be 12% without GNPs. When the air from the operator’s mouth was analyzed just after rinsing with an antiseptic mouthwash, the ethanol content was very high (3.5 v/v%). The background level was reached only after rinsing with water

Physicochemical Properties and Atomic-Scale Interactions in Polyaniline (Emeraldine Base)/Starch Bio-Based Composites: Experimental and Computational Investigations

The processability of conductive polymers still represents a challenge. The use of potato starch as a steric stabilizer for the preparation of stable dispersions of polyaniline (emeraldine base, EB) is described in this paper. Biocomposites are obtained by oxidative polymerization of aniline in aqueous solutions containing different ratios of aniline and starch (% w/w). PANI-EB/Starch biocomposites are subjected to structural analysis (UV-Visible, RAMAN, ATR, XRD), thermal analysis (TGA, DSC), morphological analysis (SEM, Laser Granulometry), and electrochemical analysis using cyclic voltammetry. The samples were also tested for their solubility using various organic solvents. The results showed that, with respect to starch particles, PANI/starch biocomposites exhibit an overall decrease in particles size, which improves both their aqueous dispersion and solubility in organic solvents. Although X-ray diffraction and DSC analyses indicated a loss of crystallinity in biocomposites, the cyclic voltammetry tests revealed that all PANI-EB/Starch biocomposites possess improved redox exchange properties. Finally, the weak interactions at the atomic-level interactions between amylopectin–aniline and amylopectin–PANI were disclosed by the computational studies using DFT, COSMO-RS, and AIM methods

Homogenous UV/Periodate Process for the Treatment of Acid Orange 10 Polluted Water

The photoactivated periodate (UV/IO4−) process is used to investigate the degradation of acid orange 10 (AO10) dye. The photodecomposition of periodate ions produces highly reactive radicals (i.e., •OH, IO3•, and IO4•) that accelerate dye degradation. Increasing the initial concentration of periodate to 3 mM enhances the dye removal rate, but over 3 mM periodate, the degradation rate slows down. On the contrary, increasing initial dye concentrations reduces the degradation performance. pH is the most critical factor in AO10 breakdown. Salts slow down the degradation of the dye. However, UV/IO4− is more efficient in distilled water than natural water. Even at low concentrations, surfactants may affect the dye’s decomposition rate. The addition of sucrose reduced the breakdown of AO10. Although tertbutanol is a very effective •OH radical scavenger, it does not affect the dye breakdown even at the highest concentrations. Accordingly, the AO10 degradation is a non-•OH pathway route. According to retrieved data, the photoactivated periodate method eliminated 56.5 and 60.5% of the initial COD after 60 and 120 min of treatment time; therefore, it can be concluded that the UV/IO4− system may treat effluents, especially those containing textile dyes

Adsorptive removal of cationic and anionic dyes on a novel mesoporous adsorbent prepared from diatomite and anionic cellulose nanofibrils: Experimental and theoretical investigations

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Exploring the Efficiency of Algerian Kaolinite Clay in the Adsorption of Cr(III) from Aqueous Solutions: Experimental and Computational Insights.

International audienceThe current study comprehensively investigates the adsorption behavior of chromium (Cr(III)) in wastewater using Algerian kaolinite clay. The structural and textural properties of the kaolinite clay are extensively characterized through a range of analytical methods, including XRD, FTIR, SEM-EDS, XPS, laser granulometry, N2 adsorption isotherm, and TGA–DTA. The point of zero charge and zeta potential are also assessed. Chromium adsorption reached equilibrium within five minutes, achieving a maximum removal rate of 99% at pH 5. Adsorption equilibrium is modeled using the Langmuir, Freundlich, Temkin, Elovich, and Dubinin–Radushkevitch equations, with the Langmuir isotherm accurately describing the adsorption process and yielding a maximum adsorption capacity of 8.422 mg/g for Cr(III). Thermodynamic parameters suggest the spontaneous and endothermic nature of Cr(III) sorption, with an activation energy of 26.665 kJ/mol, indicating the importance of diffusion in the sorption process. Furthermore, advanced DFT computations, including COSMO-RS, molecular orbitals, IGM, RDG, and QTAIM analyses, are conducted to elucidate the nature of adsorption, revealing strong binding interactions between Cr(III) ions and the kaolinite surface. The integration of theoretical and experimental data not only enhances the understanding of Cr(III) removal using kaolinite but also demonstrates the effectiveness of this clay adsorbent for wastewater treatment. Furthermore, this study highlights the synergistic application of empirical research and computational modeling in elucidating complex adsorption processes

Application of statistical physical, DFT computation and molecular dynamics simulation for enhanced removal of crystal violet and basic fuchsin dyes utilizing biosorbent derived from residual watermelon seeds (Citrullus lanatus)

This study investigates the use of watermelon seeds (Citrullus lanatus), a plentiful and cost-effective biosorbent, for the removal of basic fuchsin (BF) and crystal violet (CV) dyes from aqueous solutions. Characterization of the biosorbent was conducted using Fourier Transform Infrared Spectroscopy (FT-IR), X-Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM), while Brunauer–Emmett–Teller (BET) analysis revealed a specific surface area (SBET) of 54.50 m² g−1, highlighting its mesoporous structure advantageous for adsorption. Adsorption isotherms were best described by the Langmuir model, indicating monolayer adsorption with high correlation coefficients (R² values of 0.9959 for CV and 0.9978 for BF) and notable adsorption capacities of 139.2493 mg g−1 for CV and 238.80501 mg g−1 for BF. Thermodynamic analysis confirmed the spontaneous and exothermic nature of the adsorption, driven by molecular interactions. To elucidate the adsorption mechanism at the molecular level, we employed Density Functional Theory (DFT) calculations, Molecular Dynamics (MD) simulations, and Non-Covalent Interaction (NCI) analysis. These computational methods provided insights that closely aligned with experimental data, establishing a robust theoretical-experimental framework for understanding dye adsorption by watermelon seed biosorbent. The practical implications of our findings are significant, suggesting that watermelon seed biosorbent can be effectively scaled up for industrial effluent treatment in continuous systems. The study underscores the potential of utilizing this sustainable and economically viable biosorbent for environmental remediation, offering a promising alternative to conventional adsorbents with its high efficiency and lower sensitivity to environmental conditions such as pH and temperature

A microconductometric ethanol sensor prepared through encapsulation of alcohol dehydrogenase in chitosan: application to the determination of alcoholic content in headspace above beverages

International audienceA conductometric transducer is proposed for the first time for the detection of ethanol vapor. This ethanol microsensor is prepared by encapsulation of alcohol dehydrogenase (ADH) in chitosan. Interdigitated electrodes fabricated by silicon technology were used. The electrodeposition of chitosan allows the addressing of the chitosan film on the microconductometric devices and to encapsulate ADH and nicotinamide adenine dinucleotide (NAD?), which was monitored by FTIR. The analytical performance of the ethanol microsensor was determined in gaseous methanol, ethanol, and acetone samples, collected from the headspace above aqueous solutions of known concentration. The response time (tRec) of the sensor varies from 7 to 21 s from lower concentrations to higher concentrations. The detection limit is 0.12v/v % in the gas phase, correspondingto 0.22 M in the liquid phase. The relative standard deviation for the same sensor is from 12% for lower concentrations to 2% for higher concentrations. The ethanol sensor presents 2.6 times lower sensitivity for methanol and 28.3 times lower sensitivity for acetone. A detection of ethanol in the headspace of a red wine sample lead to an alcohol content in good agreement with the value given by the producer

Anti-corrosion performance of dehydroacetic acid thiosemicarbazone on XC38 carbon steel in an acidic medium

Dehydroacetic acid thiosemicarbazone (DHATSC) was tested for its ability to suppress corrosion on mild steel XC38 (MS XC38) by measuring its effects by electrochemical impedance spectroscopy (EIS), weight loss (WL), and potentiodynamic polarization (PDP). Using weight loss tests and potentiodynamic polarization, the corrosion inhibiting efficiency (IE) of DHATSC for MS XC38 in 1.0 M HCl solution was calculated. The data showed that DHATSC was highly inhibitory, with increasing effectiveness as the inhibitor concentration increased. In 1 M HCl, the PDP curves showed that DHATSC was a mixed-type inhibitor. In addition to the EIS findings, the adsorption of DHATSC was also validated by analyzing the charge transfer resistance (Rct) values of the MS XC38 surface. At room temperature, the most outstanding corrosion inhibition efficiency as determined by weight loss was 78%; however, the PDP method obtained 94% at a concentration of 200 ppm. With a standard free energy (Gads) of −6.90 KJ.mol-1 for the adsorption stage, the Langmuir isotherm offered the most accurate description of DHATSC adsorption. The inhibitor has a nanocrystalline structure, measured by X-ray diffraction (XRD), with a mean crystallite size (D) of 56.11 nm. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analyses verified the mild steel's surface analysis. The theoretical calculations generally agreed with the experimental findings to a high degree

The Removal of a Textile Dye from an Aqueous Solution Using a Biocomposite Adsorbent

The adsorption mechanisms of methylene blue (MB) onto olive waste (residue) treated with KOH (OR-KOH) and onto an OR-KOH and PEG–silica gel composite (OR-KOH/PEG-SG) at various temperatures were investigated using a combination of experimental analysis and Monte Carlo ab-initio simulations. The effects of adsorption process variables such as pH, temperature, and starting adsorbate concentration were investigated. The experimental data were fitted to Langmuir and Freundlich models. The maximum adsorption capacities of MB onto OR-KOH and OR-KOH/PEG-SG adsorbents reached values of 504.9 mg/g and 161.44 mg/g, respectively. The experimental FT-IR spectra indicated that electrostatic attraction and hydrogen bond formation were critical for MB adsorption onto the adsorbents generated from olive waste. The energetic analyses performed using Monte Carlo atomistic simulations explained the experimental results of a differential affinity for the investigated adsorbents and confirmed the nature of the interactions between methylene blue and the adsorbents to be van der Waals electrostatic forces

Electrochemical and Computational Approaches of Polymer Coating on Carbon Steel X52 in Different Soil Extracts

Using stationary electrochemical, polarization resistance, cathodic charging, transient electrochemical impedance spectroscopy, and theoretical and molecular mechanics studies, epoxy polymer-coated carbon steel specimens’ ability to protect metals from corrosion in various soil extracts was examined. According to the polarization resistance tests results, the polymer coating remained stable for 60 days in all three soil extracts, with a 90% efficiency for the steel coated in Soil Extract A, indicating that the sandy soil is less aggressive than the other two. The aggressiveness of clay soil was confirmed by the fact that a polymer-coated steel rod in the clay soil extract experienced a corrosion current density of 97 µA/cm2. In contrast, the same rod in sandy soil had a current density of 58 µA/cm2. The coating’s good adsorption contact with the metal surface was further guaranteed by molecular dynamics simulations, which provided atomic-level evidence of the epoxy molecule’s adsorption behavior (geometry) and adsorption energy on the carbon steel surface