Determination of hydroquinone in food and pharmaceutical samples using a voltammetric based sensor employing NiO nanoparticle and ionic liquids

A Sensitive Hydroquinone Amperometric Sensor Based on a Novel Palladium Nanoparticle/Porous Silicon/Polypyrrole-Carbon Black Nanocomposite

Exposure to hydroquinone (HQ) can cause various health hazards and negative impacts on the environment. Therefore, we developed an efficient electrochemical sensor to detect and quantify HQ based on palladium nanoparticles deposited in a porous silicon-polypyrrole-carbon black nanocomposite (Pd@PSi-PPy-C)-fabricated glassy carbon electrode. The structural and morphological characteristics of the newly fabricated Pd@PSi-PPy-C nanocomposite were investigated utilizing FESEM, TEM, EDS, XPS, XRD, and FTIR spectroscopy. The exceptionally higher sensitivity of 3.0156 μAμM^-1 cm^-2 and a low limit of detection (LOD) of 0.074 μM were achieved for this innovative electrochemical HQ sensor. Applying this novel modified electrode, we could detect wide-ranging HQ (1-450 μM) in neutral pH media. This newly fabricated HQ sensor showed satisfactory outcomes during the real sample investigations. During the analytical investigation, the Pd@PSi-PPy-C/GCE sensor demonstrated excellent reproducibility, repeatability, and stability. Hence, this work can be an effective method in developing a sensitive electrochemical sensor to detect harmful phenol derivatives for the green environment.

Fabrication of CeO2/GCE for Electrochemical Sensing of Hydroquinone

Hydroquinone is a widely used derivative of phenol which has a negative influence on human beings and the environment. The determination of the accurate amount of hydroquinone is of great importance. Recently, the fabrication of an electrochemical sensing device has received enormous attention. In this study, we reported on the facile synthesis of cerium dioxide (CeO₂) nanoparticles (NPs). The CeO₂ NPs were synthesized using cerium nitrate hexahydrate as a precursor. For determining the physicochemical properties of synthesized CeO₂ NPs, various advanced techniques, viz., powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS), were studied. Further, these synthesized CeO₂ NPs were used for the modification of a glassy carbon electrode (CeO₂/GCE), which was utilized for the sensing of hydroquinone (HQ). A decent detection limit of 0.9 µM with a sensitivity of 0.41 µA/µM cm² was exhibited by the modified electrode (CeO₂/GCE). The CeO₂/GCE also exhibited good stability, selectivity, and repeatability towards the determination of HQ.

Nanocomposites based on quasi-networked Au1.5Pt1Co1 ternary alloy nanoparticles and decorated with poly-L-cysteine film for the electrocatalytic application of hydroquinone sensing

A mildly one-pot method is developed for the synthesis of quasi-networked Au_1.5Pt₁Co₁ ternary alloy nanoparticles (TANPs) at room temperature through the co-reduction of AuCl₄^-, PtCl₆^- and Co²⁺ with hydrazine hydrate. Characterizations of XRD, XPS, HRTEM, EDS and SAED successfully reveal the crystal structure, composition, valence and morphology of Au_1.5Pt₁Co₁ TANPs, respectively. The glassy carbon electrode (GCE) modified by Au_1.5Pt₁Co₁ TANPs with good dispersion and multi-density surface defects occupies the optimal electrochemical active surface area (ECSA). After the coated poly-L-cysteine (P-L-Cys) film on the Au_1.5Pt₁Co₁/GCE surface, the morphology, element mapping and surface roughness of the P-L-Cys/Au_1.5Pt₁Co₁/GCE are investigated via FESEM and AFM to verify continuous electrode modification processes. The electrochemical behaviors of the composite electrode for hydroquinone (HQ) are evaluated by cyclic voltammetry (CV) with interfacial properties of adsorption and diffusion. Differential pulse voltammetry (DPV) for HQ electrochemical sensing at 0.10 V (vs. SCE) exhibits two linear response ranges from 0.1 to 30 and 30-200 μM, respectively. A low detection limit (S/N = 3) of 0.045 μM is obtained with a sensitivity of 4.247 μA μM^-1·cm^-2. The resulting P-L-Cys/Au_1.5Pt₁Co₁/GCE also presents ascendant selectivity, repeatability, reproducibility and stability. In addition, the established method is applied to the assessment of the HQ level in real water samples (mineral water, tap water and lake water) with the satisfactory results of spiked recoveries. The sensor may become a promising tool for the trace analysis of the electroactive substance in food or environmental samples.

Magnetic solid phase extraction of bisphenol A, phenol and hydroquinone from water samples by magnetic and thermo dual-responsive core-shell nanomaterial

Present study prepared a new magnetic and thermo dual-responsive core-shell nanomaterial (Fe@SiO₂@poly(N-isopropylacrymide-co-methacrylic acid, Fe@SiO₂@PNIPAM-co-MAA), which was characterized by transmission electron microscopy and X-ray diffraction techniques. The new nanomaterials integrated with the magnetism of nanoscale zero valent iron material and thermo-response of the copolymers, and were utilized to investigate the adsorption capacity for typical phenols such as bisphenol A, phenol and hydroquinone from water samples, and the results showed that the magnetic and thermo dual-responsive core-shell nanomaterial exhibited good adsorption ability to typical phenols. Based on these, a sensitive method was developed for the determination of bisphenol A, phenol and hydroquinone using as-prepared magnetic nanoparticles as the magnetic solid phase extraction sorbent prior to high performance liquid chromatography coupled with variable wavelength detection. Under the optimal conditions, linear linearity was obtained over the range of 0.1-500 μg L^-1 with the correlation coefficients (r²) above 0.996. The detection limits of three analytes were in the range of 0.019-0.031 μg L^-1, and the precisions were all less than 4.8% (n = 6). The developed method was evaluated with real water samples and excellent spiked recoveries in the range of 94.0-105.4% were achieved. These results indicated that the proposed method was a robust analytical tool and a useful alternative for routine analysis of such pollutants.

Electrochemical treatment of pharmaceutical wastewater through electrosynthesis of iron hydroxides for practical removal of metronidazole

Antibiotics as the severe contaminants of aqueous environments were received growing attention during the last decades. The current work is the first report on investigating the potency and efficiency of electrocoagulation process in the successful removal of metronidazole (MNZ) from pharmaceutical wastewater using response surface methodology based on central composite design. The applied method by optimizing the independent and combined effects of significant variables which affecting the EC process enhanced the removal efficiency of MNZ. Analysis of variance was applied to verify the significance of independent variables solely and their interactions. The best removal efficiency of 100% found under the optimal operating condition of initial MNZ concentration 21.6 mg L^-1, pH 8.2, current density 6.0 mA cm^-2, inter-electrode distance 3 cm, and reaction time of 14.6 min. Isotherm investigations revealed that the Langmuir model with the R² of 0.994 best fitted to the obtained experimental equilibrium results. The fast adsorption of MNZ on the surface of Fe(OH)₃ and [Fe(OH)₂]⁺ with the equilibrium time of 15 min confirmed that the kinetics of the electrocoagulation process follow the pseudo-second-order model (R² = 0.962). The electrocoagulation process under the optimal operating condition revealed that the electrical energy consumption per each m³ of treated pharmaceutical wastewater, per each g of MNZ, removed, and per each kg of Fe electrode consumed, were found to be 0.516 kWh m^-3, 0.0234 kWh g^-1, and 0.0436 kWh kg^-1, respectively.

Structural Assessment and Catalytic Oxidation Activity of Hydrophobized Whey Proteins

Chemical modification of whey proteins allows manipulation of their characteristics, such as surface charge and hydrophobicity. Herein, we report the influence of hydrophobization accomplished by a preacetylation stage and a subsequent combined acetylation-heating process on some characteristics of whey proteins. Hydrophobization extensively (≥90%) acetylated the available free amino groups of whey proteins. The produced protein particles were nanoscaled (75 nm) and had a significantly low isoelectric point (3.70). Hydrophobization increased the β-sheet content of whey proteins and significantly decreased the solvent exposure of tyrosine residues. It also conferred a less compact tertiary structure to the proteins and decreased the extent of disulfide-bond formation by heating. The mobility of α-lactalbumin in nonreducing electrophoresis gel increased as a consequence of hydrophobization. Then, the ability of whey proteins to catalyze hydroquinone autoxidation was examined, and it was found that the activity decreased as a result of hydrophobization. The catalytic activity of the proteins was associated with the free-amino-group content, which determined the extent of cation-π attractive interactions; ζ-potential, which determined the extent of anion-π repulsive interactions; and π-stacking between hydrophobic residues and the electron cloud of the quinone ring.

Comparison of wastewater treatment plants based on the emissions of microbiological contaminants

This article presents the current and important results of bioaerosol studies which allow for the comparison of microbial contamination of air in 11 wastewater treatment plants (WWTPs), which differed in terms of capacity from 350 to 200,000 m³/day. The abundance of mesophilic bacteria, M+ and M- Staphylococcus, Pseudomonas fluorescens, Actinobacteria, coliform and psychrophilic bacteria, and microscopic fungi was determined. Additionally, the air temperature, relative humidity, wind velocity, and direction were also analyzed at each research station. The obtained very numerous results of bioaerosol and climate parameter studies were subjected to statistical analysis. The results regarding the minimum, maximum, and median abundance of the studied bacteria and microscopic fungi at 11 WWTPs and in background studies at control stations were presented in tables. Additionally, basic descriptive statistics for all studied microorganisms at specific seasons were presented. It was established that at the areas of WWTPs, the microscopic fungi were present that the highest concentrations (ranging from 0 to 1,148,530 CFU m^-3), followed by psychrophilic bacteria (ranging from 40 to 225,000 CFU m^-3) and mesophilic bacteria (ranging from 0 to 195,000 CFU m^-3). The novel elaboration of bioaerosol study results based on cluster analysis and determination of a dendrogram allowed to compare the studied WWTPs. The similarity was decided based on the type of studied microorganisms and their dominance and abundance, while no similarities were observed in terms of capacity. In order to investigate the relation between the abundance of bacterial groups as well as microscopic fungi and microclimatic parameters (air temperature and humidity), a calculation of Spearman's range correlation coefficients was conducted.

In situ generation of hydroxyl radical for efficient degradation of 2,4-dichlorophenol from aqueous solutions

Since 2,4-dichlorophenol (2,4-DCP) as a priority pollutant is used in numerous industrial processes, its removal from the aqueous environment is of utmost importance and desire. Herein, the authors describe an electrochemical treatment process for efficient removal of 2,4-DCP from aqueous solutions using electro-Fenton (EF) process. Response surface methodology (RSM) was applied to optimize the operating parameters. Analysis of variance (ANOVA) confirmed the significance of the predicted model. The effect of independent variables on the removal of 2,4-DCP was investigated and the best removal efficiency of 98.28% achieved under the optimal experimental condition including initial pH of 3, H₂O₂ dosage of 80 μL, initial 2,4-DCP concentration of 3.25 mg L^-1, current density of 3.32 mA cm^-2, and inter-electrode distance of 5.04 cm. The predicted removal efficiency was in satisfactory agreement with the obtained experimental removal efficiency of 99.21%. According to the obtained polynomial model, H₂O₂ dosage revealed the most significant effect on degradation process. The kinetic investigation revealed that the first-order model with the correlation coefficient of 0.9907 and rate constant (K_app) of 0.831 min^-1 best fitted with the experimental results. Generation of the hydroxyl radicals throughout the EF process controlled the degradation process.