Mmol Dm Research Articles

Technosols Made from Iron Mine Tailings and Construction and Demolition Waste as an Alternative for Sustainable Solid Waste Management

ABSTRACTBrazil faces urgent environmental challenges due to large waste production from mining and construction activities particularly regarding the disposal and management of the solid waste generated by these activities. The extraction of iron ore and the storage of tailings in dams, most of which are at imminent risk of rupture, represent foretold environmental disasters. Additionally, the disposal of construction waste raises environmental concerns due to the decreasing vailability of inert landfill space. To address these challenges, we evaluated the potential of Technosols made from construction and demolition waste (CDW) and iron mining tailing (IMT) in different proportions (60:40, 70:30, 80:20, and 100% of IMT and CDW, respectively) to support grass development. The Technosols were compared to a natural soil (Haplic Ferralsol). The soils were cultivated with Urochloa brizantha cv. Marandu in a field experiment conducted for 120 days. At the end of experiment, soil samples were collected and analyzed their chemical, physical, and mineralogical attributes, while plants were analyzed for dry biomass. Plants cultivated in Technosols exhibited dry biomass production 3.3‐fold (825 ± 270 g) greater than those cultivated in the natural soil (251 ± 77 g). Higher biomass production in the Technosols, especially in the TEC70:30, was associated with the favorable chemical conditions of these soils, such as slightly neutral pH (~7.5), higher cation exchange capacity (68.1 ± 12.4 mmol dm−3) and nutrient availability, especially Ca and P (57.8 ± 0.8 and 28.2 ± 0.4 mmol dm−3, respectively). These results aim to provide insights for the effective use of different Technosols in mitigating environmental impacts and promoting sustainable land and waste management practices, primarily to prevent future environmental disasters.

Molecular mechanism of alpha- and beta-cyclodextrin assisted refolding of SDS-induced amyloid fibrils of myoglobin

The formation of amyloids arises from the misfolding or unfolding of various proteins. This study investigated the impact of chemical chaperones, alpha-cyclodextrin (α-CD) and beta-cyclodextrin (β-CD), on the solubilization and defibrillation of sodium dodecyl sulfate (SDS)-induced myoglobin (Mb) amyloid fibrils. Amyloid fibril was developed in Mb in the presence of 0.8 mmol dm−3 SDS at pH 4.5. Subsequently, SDS-induced Mb amyloid was incubated with varying concentrations of α-CD and β-CD at the same pH. Our turbidity, intrinsic fluorescence, SDS-PAGE, and transmission electron microscope data showed that α-CD (2.1 mmol dm−3) was more efficiently solubilized the SDS-treated Mb aggregates than β-CD (4.0 mmol dm−3). But, another interesting phenomenon was observed with β-CD. The ThT fluorescence and far-UV CD data suggested that amyloid defibrillation by β-CD (0.6 mmol dm−3) was more effective than α-CD (0.9 mmol dm−3). The intrinsic fluorescence and far-UV CD data also showed that SDS-treated Mb regained native-like structure at lower α-CD compared to β-CD. Overall our data suggest that α-CD was more efficient in aggregate solubilization while β-CD was more effective in amyloid defibrillation. Understanding the mechanisms underlying cyclodextrins’ actions may serve as a basis for identifying potential drugs to suppress amyloid fibril formation effectively. This research provides valuable insights into mitigating amyloid-related pathologies.

Moment analysis method for determination of rate constants of solute permeation across interface of spherical molecular aggregates by means of high-performance liquid chromatography

A moment analysis method was developed for the study of solute permeation at the interface of spherical molecular aggregates. At first, new moment equations were developed for determining the partition equilibrium constant (Kp) and permeation rate constants (kin and kout) of solutes from the first absolute (μ1A) and second central (μ2C) moments of elution peaks measured by using high-performance liquid chromatography (HPLC). Then, the method was applied to the analysis of mass transfer phenomena of three solutes, i.e., hydroquinone, resorcinol, and catechol, at the interface of sodium dodecylsulfate (SDS) micelles. HPLC data were measured by using an ODS column and an aqueous phosphate buffer solution (pH = 7.0) as the mobile phase solvent. Pulse response experiments were conducted while changing SDS concentration (5 - 20 mmol dm−3) in the mobile phase under the conditions that the surface of ODS stationary phase was dynamically coated by SDS monomers. In order to demonstrate the effectiveness of the moment analysis method using HPLC, the values of Kp, kin, and kout were determined for the three solutes as 35 - 69, 2.4 × 10−8 - 1.4 × 10−6 m s−1, and 7.0 × 10−10 - 2.1 × 10−8 m s−1, respectively. Their values increase with an increase in the hydrophobicity of the solutes. The method has some advantages for the study of interfacial solute permeation of molecular aggregates. For example, neither immobilization nor chemical modification of both solute molecules and molecular aggregates is required when elution peaks are measured by using HPLC. Interfacial solute permeation takes place in the mobile phase without any chemical reaction or physical action on molecular aggregates. The values of Kp, kin, and kout were analytically determined from those of μ1A and μ2C by using the moment equations. The results of this study must contribute to the dissemination of an opportunity for studying the interfacial solute permeation of molecular aggregates to many researchers because of extremely high versatility of HPLC.

Influence of Amino Acids on Calcium Oxalate Precipitation in Systems of Different Chemical Complexity

The mechanisms and conditions under which urinary stones, pathological biominerals in the kidneys and bladder, are formed have not yet been fully clarified. This study aims to understand the role of the system complexity and seven different amino acids (alanine, phenylalanine, glycine, serine, cysteine, histidine, and aspartic acid) in the spontaneous precipitation of calcium oxalate. To elucidate these effects, the conditions simulating hyperoxaluria (ci(Ca2+) = 7.5 mmol dm−3 and ci(C2O42−) = 6.0 mmol dm−3) were used for the first time. In this work, systematic research on calcium oxalate precipitation was performed in three systems of different chemical complexities: (a) only calcium and oxalate ions, (b) increased ionic strength, and (c) artificial urine at two initial pHs (pHi = 5.0 and 9.0). In all the investigated systems, the dominant precipitation of calcium oxalate monohydrate (COM) was observed, except in the artificial urine system at pHi = 9.0, in which a mixture of COM and calcium oxalate dihydrate (COD) was obtained. In all the investigated systems, a significant influence of the selected amino acids on the morphology and crystal growth of COM was observed, with more pronounced changes at pHi = 9.0. Overall, polar amino acids and nonpolar phenylalanine inhibit the growth of COM, which is a more pathogenic hydrate form. The artificial urine system proved to be more relevant for the observation of effects relevant to kidney stone formation in the human body.

Assessment of rapid initiators and long-lasting nutrients for developing biological permeable reactive barriers to treat mine-contaminated groundwater

ABSTRACT The formation of mine-contaminated groundwater as a result of acidic mine drainage from the oxidation of sulfur-containing minerals entering the groundwater. Biological permeable reactive barrier (Bio-PRB) technology is excellent for the remediation of mine-contaminated groundwater. Usually, the organic substrates utilized in Bio-PRB are a combination of rapid initiators, which are readily bioavailable, and long-lasting nutrients, which are more difficult to degrade. Herein, we investigated the effectiveness of three rapid initiators and three long-lasting nutrients to remove sulfate from simulated mine-contaminated groundwater via simulated column experiments. The rapid initiators comprised crude glycerol, sodium acetate, and industrial syrup (IS), and the long-lasting nutrients included biodiesel emulsified oil, soybean oil emulsified oil, and high-carbon alcohol emulsified oil (HO). Microorganisms were stimulated using IS to create a sulfate reduction system owing to its high total organic carbon content (24.30 g L−1), achieving optimal sulfate removal rate (1.69 mmol dm−3 d−1). The fastest (2.93 mmol dm−3 d−1) and highest (88%) sulfate removal rates were achieved using HO, which is probably associated with the ability of HO to provide the most suitable C/N ratio (111.75) and induce the growth of sulfate-reducing bacteria (SRB) for substrate degradation. Conversely, a high concentration of sulfate reduction products inhibited SRB growth in the HO column. The addition of organic materials promoted SRB growth and various organic substrate–degrading bacteria. Furthermore, the competitive growth of methanogens (86.6%) may be responsible for the decrease in the relative abundance of SRB during the later stages of the experiment in the HO column.

Capillary zone electrophoresis method for quantification of therapeutic peptide glatiramer acetate

This study presents the development and validation of a novel capillary zone electrophoresis method for the precise determination of glatiramer acetate and its amino acid constituents. A 120 mmol dm−3 phosphoric acid solution adjusted to pH 1.9 with Tris, supplemented with 20 mmol dm−3 triethylamine to achieve a final of pH 2.1, resulted in a repeatable analysis of glatiramer acetate. The method demonstrated a limit of detection and quantification of 39.2 µg cm−3 and 130.7 µg cm−3, respectively. This method allows for the rapid control of glatiramer acetate-based pharmaceuticals and distinguishes glatiramer acetate from the amino acids used in its synthesis.Graphical abstract

Molecularly imprinted polymer nanoparticle-carbon nanotube composite electrochemical gas sensor for highly selective and sensitive detection of methanol vapour.

An electrochemical gas sensor has been fabricated using molecularly imprinted polymer nanoparticles (nanoMIPs) and multiwalled carbon nanotubes on screen-printed electrodes. Methanol vapour was chosen as the target due to its toxicity as its suitability as a model for more harmful pollutant gases. The sensor functions under ambient conditions and in the required concentration range, in contrast to all previous MIP-based gas sensors for methanol. The sensitivity of the sensor was greatly improved by the addition of multiwall carbon nanotubes, resulting in a limit of detection of approximately 10 ppm. The nanoMIPs provide an inherent selectivity for the target inherent in its design. Selectivity studies were performed with structurally analogous alcohols at various concentrations, demonstrating selectivity for methanol 12.1 times that for ethanol at 2 mmol dm-3 and 4.2 times that for ethanol at 1 mmol dm-3. Interactions with isopropanol and n-propanol were found to be non-specific, and the response to water was negligible. This demonstrates an improvement over previous methanol gas sensors based on molecularly imprinted polymers. No response was observed with carbon nanotubes alone, and no selectivity was observed with non-imprinted equivalents of the nanoMIP sensor. The resulting device is by far the most practical MIP-based instrument for methanol gas sensing thus far described in the literature, being the only example capable of functioning at the necessary methanol vapour concentrations and at the required temperature and humidity. With the selectivity and sensitivity described and the simple design, the developed device provides a substantial advance in the field of molecularly imprinted gas sensors.

Prostorna i sezonska raspodjela partikularnog fosfora u obalnim vodama i otvorenom moru srednjeg Jadrana

The seasonal and spatial distributions of particulate phosphorus (PP) in the water column of the coastal area and open sea of the middle Adriatic Sea area were investigated for the first time. The relationship between PP and two other important forms of phosphorus (dissolved inorganic phosphorus (DIP), and organic phosphorus (P-ORG)), and the relationship between PP and other nutrients (nitrogen and silicon salts) and oceanographic parameters (temperature, salinity, oxygen saturation, chlorophyll a) from the water column were also examined. PP concentrations ranged from 0.007 μmol dm-3 in the open sea near Palagruža archipelago to 0.589 μmol dm-3 in the Krka River estuary. In the coastal area, PP concentrations were highest in autumn and lowest in winter. The vertical distribution of PP concentrations in the water column of the coastal area were highest in the surface layer during most of the year due to input of PP by freshwater inflows. In the open sea area, there were no significant seasonal or vertical differences in the distribution of PP concentrations in thewater column. Seasonal analysis of the total phosphorus pool (PP, DIP and P-ORG) in the water column indicated that PP and P-ORG concentrations were higher in the coastal area compared to the open sea, while DIP concentrations were comparable.The results further demonstrate that PP can be an important fraction of the total phosphorus pool. A significant positive correlation was found between PP and chlorophyll a, indicating that PP was mainly of biological origin, and with nutrient salts of nitrogen and silicon, while a negative correlation was found with salinity.

Electrochemical Reduction from CO2 to CH4 By Electrodeposited Cu/L-Histidine Hybrid Materials

The electrochemical reduction technology of carbon dioxide (CO2) is attracting attention due to it can convert CO2 into a useful resource with zero emissions by using surplus electricity and renewable energy. For achieving efficient electrolytic reduction of CO2, the development of a high active electrocatalysts is required. Copper (Cu) is the only metal that is capable of electrochemically converting CO2 to hydrocarbons, but the high overpotential of hydrocarbon formation and the low selectivity of the reduction products have been problems. One of the solutions to these problems is the hybridization of metal and organic materials, in which the metal serves as the CO2 reduction reaction sites and the organic material stabilizes the intermediates [1]. In the present study, we have demonstrated electrochemical reduction of CO2 by electrodeposited Cu loading L-Histidine (L-His) which is expecting stabilization of CO2 reductive intermediates hybrids.The electrodeposited Cu/L-His hybrids was obtained by a constant current electrolysis at -1.0~-4.5 mA cm-2 for 1 C cm-2 from the aqueous solutions containing 10 mmol dm-3, CuSO4･5H2O, 0.1 mol dm-3 Na2SO4, and 0.5~20 mmol dm-3 L-His in a three-electrode cell with carbon paper (CP) as the working electrode, platinum wire as the counter electrode, and Ag/AgCl as the reference electrode. The pH of electrolytic bath was controlled between 1.10 and 4.07 by adding H2SO4. The electrochemical reduction of CO2 has been carried out by a constant potential electrolysis at -1.27 V vs. RHE of 0.5 mol dm-3 KHCO3 aqueous solutions saturated with CO2. The amount of reductive gas products was quantified by GC-MS and GC-TCD.The changing the color from pale blue to deep blue was observed by adding L-His into electrolytic bath containing Na2SO4 and CuSO4･5H2O. As increasing concentration of L-His, absorption peak measured by UV-Vis was shifting from around 800 nm originated [Cu(H2O)4]2+ to around 630 nm. The shift was not observed above Cu2+ : L-His = 1 : 2 for molar concentration ratio, therefore, it was considered that Cu2+ and L-His form a complex of [Cu(L-His)2]2+ in aqueous solution. Thus, electrodeposition of Cu/L-His has been tried from Cu2+ : L-His = 1 : 2 aqueous solutions but electrodeposited Cu/L-His cannot achieve. As decreasing pH of electrolytic bath with fixing Cu2+ : L-His = 1 : 2, the absorption peak originated [Cu(L-His)2]2+ was shifting to [Cu(H2O)4]2+ absorption peak. Below pH = 1.7, the absorption peak had been shifted to [Cu(H2O)4]2+ completely and the precipitate was obtained in this condition. The hybridization Cu and L-His was confirmed by Raman spectra. Not only Cu, L-His peaks but also new peak originated L-His adsorbs to Cu were observed. CP has fiber like structure but electrodeposited Cu and Cu/L-His were precipitated such coating CP fiber. The particle size of Cu/L-His hybrids was more homogeneous, and the particles were more densely packed together compared to the pure Cu. However, changing diffraction patterns and peak broadening due to loading organic components in XRD were not observed.The electrochemical reductive reaction of CO2 on ED Cu has been conducted and the faradic efficiency (FE) of CO2 reductive gas product were calculated (Figure). Electrodeposited Cu (ED Cu) showed dramatically improvement of FE from CO2 to CH4 compared to copper foil (Cu foil). Furthermore, the L-His loading electrodeposited Cu (ED Cu/L-His) was more improved than ED Cu. Worthy of a special mention, the amount of hydrogen generation was reduced dramatically by introducing L-His. It can be considered that a reaction field was formed in which the CO2 reduction reaction preferentially takes place over hydrogen evolution. As increasing the concentration of L-His between 0.5~20 mmol dm-3, the FE from CO2 to CH4 goes high until 1.0 mmol dm-3 and then goes down, therefore, it can be observed that high L-His loading inhibits CO2 electrochemical reduction.[1] S. Jia et al., Angew. Chem. Int. Ed. 2021, 60, 10977–10982. Figure 1

Electrodeposition Behavior of Al-Au Alloys in AlCl3-NaCl-KCl-Aucl Molten Salt

Quartz Crystal Microbalance (QCM) has been used as a highly sensitive mass sensor. This study aims to form porous gold thin films on QCM elements and apply them to highly sensitive gas sensors by attaching selective media. Physical vapor deposition and chemical etching are known methods for forming porous Au thin films. In this study, the electrochemical formation of porous gold films in AlCl3-NaCl-KCl molten salts containing AuCl was investigated. There are few reports about electrodeposition and dissolution potentials of Au in the molten salt electrolyte. As a first step in this study, voltammogram measurements and constant potential electrolysis were performed in the electrolyte, and electrodeposition potentials of Au and Al-Au alloys were discussed.An electrolyte in this study is a mixture of 61 mol% AlCl3- 26 mol% NaCl- 13 mol% KCl molten salt. The mixture salt was melted at 443 K and AuCl was added to the molten salt. A glassy carbon plate (GC) and a pure Al wire were used as the working electrode and reference electrode, respectively. The GC plate and Au mesh were used as the counter electrode for voltammogram measurement and constant potential electrolysis, respectively. Voltammogram measurements were carried out at potential range from -0.1 to 2.4 V vs. Al/Al(Ⅲ). Constant potential electrolysis was performed in the range from -0.2 to 0.3 V with an electric charge density of 40 C cm-2. The electrodeposits were observed by scanning electron microscopy (SEM) and determined the composition of Al and Au by energy dispersive X-ray spectroscopy (EDS).Au ions concentration in the electrolyte was 2.5 mmol dm-3. In voltammogram measurements, a small cathodic current was observed at about 0.8 V, then gradually increased from 0.2 V. In the potential lower than 0 V, a drastical increase of cathodic current was observed, which was attributed to Al electrodeposition. When the potential was reversed, large anodic current flowed from 0 V and a small current peak was also observed at 0.2 V. These were considered to correspond to the dissolution of Al and Al-Au alloys, respectively. Furthermore, a relatively large anodic current peak was observed at about 2 V, which was expected to be due to the dissolution of Au. From the results of constant potential electrolysis, the Au concentration in the electrodeposits at -0.1 V and -0.2 V was less than 1 at%. At 0 V, the Au concentration in the electrodeposit increased sharply to 84 at%, and at 0.3 V it increased moderately to 89 at%. From SEM observation, the morphology of the electrodeposits at -0.1 V and -0.2 V was dense, while that at potentials more than 0 V was sponge-like.AcknowledgementsThis work was supported by JST SICORP and JPMJSC2108.

Attempts to Electrochemically Synthesize Palladium Superhydrides By High Pressure Method – Combination of Electrolytic Hydrogen Charging and Electroplating of Protective Coatings –

IntroductionIncited by the possibility of room-temperature superconductors in superhydrides, numerous them have been synthesized using a diamond anvil cell under high pressures up to several hundred GPa. Although palladium has widely researched for a long time as a prototype hydrogen-absorbing metal, the palladium superhydrides has not yet been obtained under such high pressures. A recent theorical calculation has predicted that the palladium superhydrides (e.g., PdH10) may be synthesized by combing electrolysis and high pressure1), but it is not certain whether it can be achieved. In this study, we attempted to synthesize the palladium superhydrides by using electrolytic hydrogen charging under high pressures, and subsequently applied protective coatings to suppress the hydrogen desorption from the palladium hydrides at ambient pressure.ExperimentalFigure shows a schematic illustration of the high-pressure apparatus. The high-pressure apparatus can apply the pressure of up to 400 MPa to the electrolyte in the electrolytic cell by pumping water into a sealed high-pressure vessel using a plunger pump and pressure multipliers. A cold-rolled palladium foil of 30 ~ 40 μm in thickness was used as a cathode, and a zinc plate was utilized as a soluble anode. Hydrogen was electrochemically loaded into the palladium foil at 0 V vs. Zn in an electrolyte consisting of 0.1 mol dm-3 sulfuric acid and 4.6 mmol dm-3 zinc sulfate under various pressures for 6 hours. Subsequently, the palladium foil was coated with the zinc film at constant current density 25 mA cm-2 for 120 seconds under the high pressure. The specimen was removed from the electrolytic cell in the high-pressure vessel at ambient pressure, and the hydrogen concentration of the palladium hydride PdH x was determined by thermal desorption spectroscopy. Structural analysis was conducted using X-ray diffraction and scanning electron microscopy.Results and discussionA number of bubbles were observed on the palladium foil surface during the electrolytic charging at ambient pressure. On the other hand, no bubbles were observed at 300 MPa. The zinc film with approximately 1.4 μm thick was coated on the PdH x surface after the electrolytic hydrogen charging. The hydrogen concentration of the PdH x was approximately x = 0.7 immediately after synthesis, which decreased to x = 0.2 without the zinc coating. On the other hand, the hydrogen concentration of the PdH x was maintained at least 1 week with the zinc coating. This result indicates that the zinc film acts as a barrier to hydrogen desorption from PdH x , and suggests that if the palladium superhydrides could be synthesized by electrolytic hydrogen charging under high pressure, it could be taken out to ambient pressure while maintaining its concentration.Reference1) W. Guan, R. J. Hemley, and V. Viswanathan, PNAS, 118, e2110470118 (2021) Figure 1

Experimental investigation of the responses of meadow buttercup (Ranunculus acris L.) to sodic salinity and its implications for habitat monitoring

Ranunculus acris L. is a native species widely distributed throughout Europe and is invasive in nonnative areas, causing substantial economic losses in pasture productivity. The present study examined the effects of sodic salinity on the growth and functioning of this species. Salinity stresses the germination process and seedling growth, indicating that the studied species experience serious limitations at 60–90 mmol dm−3 NaCl and cannot establish in habitats where salinity is equal to or greater than 150 mmol dm−3 NaCl. R. acris is tuned to subsaline habitats characteristic of temperate meadows, as its growth and functioning were the best when the plants were treated with 30 mmol dm−3 NaCl. Increasing salinity (60 and 90 mmol dm−3 NaCl) hampered growth, leaf morphology and photosynthesis but not mineral nutrition, as Na accumulation seemed to be the most outlined effect of NaCl application. Changes in leaf morphological characteristics coordinated well with Na content in those organs, which indicates that leaf appearance can be easily catchable sign of progressing salinity. Ultimately, progressing salinity reduces the competitiveness of the studied species, shifting its strategy to ruderal behavior, but under subsaline conditions, the strategy of this species seems to be most balanced.

Ionizing Radiation Induced Removal of Ofloxacin, Abatement of Its Toxicity and Antibacterial Activity in Various Water Matrices

The fluoroquinolone-type antibiotic ofloxacin is regularly detected in wastewaters. In this work, its hydroxyl radical (•OH) induced degradation was studied at a concentration of 0.1 mmol dm−3 in three water matrices, pure water, tap water, and purified wastewater (collected from a wastewater treatment plant). •OH was produced by γ-irradiation under conditions when it had a high yield. The •OH dosage dependencies of chemical (COD) and biochemical (BOD) oxygen demands, total organic carbon (TOC) content, oxygen uptake rate (OUR), Microtox® toxicity, and antibacterial activity values were evaluated. •OH effectively oxidized and mineralized ofloxacin; both processes were observed even at the lowest •OH dosage, 0.14 mmol dm−3 (0.5 kGy absorbed dose). When 0.28 mmol dm−3 •OH was introduced into pure or tap water, the antibacterial activity vanished. In purified wastewater, a higher dosage (0.56 mmol dm−3) was required to achieve the same effect as in pure water, due to the organic molecules of the matrix that quenched the •OH radicals. The products did not have antibacterial activity and showed little toxicity toward the test organism Vibrio fischeri. •OH preferentially attacks the pharmacophore part, the 4-quinolone unit of ofloxacin. •OH-induced reactions can be safely applied to destroy the antimicrobial potency of fluoroquinolone-type antibiotics in purified wastewater matrices.

Hydroxyl radical induced degradation of the ß-blocker Nadolol and comparison with Propranolol

The often used β-blockers Nadolol and Propranolol are regularly detected in wastewater and purified wastewater, for their elimination high energy irradiation treatment is recommended here. Both molecules are composed of an aromatic part and an oxypropanolamine side chain. The aromatic part in Propranolol contains a naphthalene unit, in Nadolol fused benzene and cyclohexane rings. This difference in the structure causes profound effect in their hydroxyl radical (•OH, main reactant in degradation of organic molecules in Advanced Oxidation Processes) reactions. In Propranolol ∼80–90% •OH attacks take place on the aromatic part and only ∼10–20% on the oxypropanolamine side chain chromophore. In the case of Nadolol these numbers are ∼70 and ∼30%. In both molecules the degradation occurs through the formation of hydroxycyclohexadienyl (main transient intermediate), α-aminoalkyl, aminium and aminyl type radicals. The first formed products of Nadolol are non-toxic or have just little toxicity, while those of Propranolol are considerably toxic. For both molecules the toxicity vanishes with the increasing amount of •OH injected into the solution (increasing dose). The non-biodegradable Nadolol and Propranolol solutions become biodegradable upon irradiation with c.a. 1 kGy dose at 0.1 mmol dm−3 concentration.

Fe-containing carbon-coated monoliths prepared by CVD in gaseous toluene abatement - parametric analysis of the Fenton process

The degradation of toluene (present in a gas stream) by the heterogeneous Fenton process was evaluated in a bubble column reactor. The process was catalyzed by macrostructured carbon-coated monoliths that were synthesized by chemical vapor deposition (CVD), which allowed carbon growth in honeycomb cordierite monoliths, while the iron (metal phase) was incorporated by adsorption. A detailed parametric study was carried out to evaluate the effect of the main variables and process operating conditions, namely channel density of the monolith, hydrogen peroxide concentration, pH and catalyst load; as process responses, the amount of toluene transferred - η, hydrogen peroxide consumption and dissolved organic carbon (DOC) concentration in the liquid phase were assessed. The maximum ratio between the toluene transferred per catalysts mass - η/W - (6.8 ×10−2 moltoluene gcat−1), with total oxidant consumption and higher intermediate compounds remaining in solution (DOC = 33 mgC dm−3), was reached when the process was performed with a monolith with a channel density of 230 cpsi, initial pH = 3.0, [catalyst] = 0.8 g dm−3, [H2O2] = 20 mmol dm−3. During all experiments, only a small amount of iron was leached from the catalyst to the liquid phase (ca. ≤1.0 wt%), proving its stability for such application; in fact, it was found that homogenous process contribution due to iron leaching towards the overall performance is ca. 10%.

Digital image colorimetry method for determination of glucose using silver nanoparticles immobilized into polymethacrylate matrix

We suggest Ag0 nanoparticles immobilized into transparent polymethacrylate matrix (PMM–Ag0) as a simple colorimetric sensor for determination of glucose. We demonstrate the capabilities of a smartphone to process the images and further analyze the information obtained by determination of glucose using PMM–Ag0 sensor. The method can be employed for glucose concentrations of 0.1–4.3 mmol dm−3, while its detection limit is 0.05 mmol dm−3.

Biogeochemical Activity of Methane-Related Microbial Communities in Bottom Sediments of Cold Seeps of the Laptev Sea

Bottom sediments at methane discharge sites of the Laptev Sea shelf were investigated. The rates of microbial methanogenesis and methane oxidation were measured, and the communities responsible for these processes were analyzed. Methane content in the sediments varied from 0.9 to 37 µmol CH4 dm-3. Methane carbon isotopic composition (δ13C-CH4) varied from -98.9 to -77.6‱, indicating its biogenic origin. The rates of hydrogenotrophic methanogenesis were low (0.4-5.0 nmol dm-3 day-1). Methane oxidation rates varied from 0.4 to 1.2 µmol dm-3 day-1 at the seep stations. Four lineages of anaerobic methanotrophic archaea (ANME) (1, 2a-2b, 2c, and 3) were found in the deeper sediments at the seep stations along with sulfate-reducing Desulfobacteriota. The ANME-2a-2b clade was predominant among ANME. Aerobic ammonium-oxidizing Crenarchaeota (family Nitrosopumilaceae) predominated in the upper sediments along with heterotrophic Actinobacteriota and Bacteroidota, and mehtanotrophs of the classes Alphaproteobacteria (Methyloceanibacter) and Gammaproteobacteria (families Methylophilaceae and Methylomonadaceae). Members of the genera Sulfurovum and Sulfurimonas occurred in the sediments of the seep stations. Mehtanotrophs of the classes Alphaproteobacteria (Methyloceanibacter) and Gammaproteobacteria (families Methylophilaceae and Methylomonadaceae) occurred in the sediments of all stations. The microbial community composition was similar to that of methane seep sediments from geographically remote areas of the global ocean.

Layer-by-Layer Deposited Multi-Modal PDAC/rGO Composite-Based Sensors.

Different environmental parameters, such as temperature and humidity, aggravate food spoilage, and different volatile organic compounds (VOCs) are released based on the extent of spoilage. In addition, a lack of efficient monitoring of the dosage of pesticides leads to crop failure. This could lead to the loss of food resources and food production with harmful contaminants and a short lifetime. For this reason, precise monitoring of different environmental parameters and contaminations during food processing and storage is a key factor for maintaining its safety and nutritional value. Thus, developing reliable, efficient, cost-effective sensor devices for these purposes is of utmost importance. This paper shows that Poly-(diallyl-dimethyl ammonium chloride)/reduced Graphene oxide (PDAC/rGO) films produced by a simple Layer-by-Layer deposition can be effectively used to monitor temperature, relative humidity, and the presence of volatile organic compounds as indicators for spoilage odors. At the same time, they show potential for electrochemical detection of organophosphate pesticide dimethoate. By monitoring the resistance/impedance changes during temperature and relative humidity variations or upon the exposure of PDAC/rGO films to methanol, good linear responses were obtained in the temperature range of 10-100 °C, 15-95% relative humidity, and 35 ppm-55 ppm of methanol. Moreover, linearity in the electrochemical detection of dimethoate is shown for the concentrations in the order of 102 µmol dm-3. The analytical response to different external stimuli and analytes depends on the number of layers deposited, affecting sensors' sensitivity, response and recovery time, and long-term stability. The presented results could serve as a starting point for developing advanced multi-modal sensors and sensor arrays with high potential for analytical applications in food safety and quality monitoring.

Characterization of a Ruthenium(II) Complex in Singlet Oxygen-Mediated Photoelectrochemical Sensing.

A water-soluble ruthenium(II) complex (L), capable of producing singlet oxygen (1O2) when irradiated with visible light, was used to modify the surface of an indium-tin oxide (ITO) electrode decorated with a nanostructured layer of TiO2 (TiO2/ITO). Singlet oxygen triggers the appearance of a cathodic photocurrent when the electrode is illuminated and biased at a proper reduction potential value. The L/TiO2/ITO electrode was first characterized with cyclic voltammetry, impedance spectroscopy, NMR, and Raman spectroscopy. The rate constant of singlet oxygen production was evaluated by spectrophotometric measurements. Taking advantage of the oxidative process initiated by 1O2, the analysis of phenolic compounds was accomplished. Particularly, the 1O2-driven oxidation of hydroquinone (HQ) produced quinone moieties, which could be reduced back at the electrode surface, biased at -0.3 V vs Ag/AgCl. Such a light-actuated redox cycle produced a photocurrent dependent on the concentration of HQ in solution, exhibiting a limit of detection (LOD) of 0.3 μmol dm-3. The L/TiO2/ITO platform was also evaluated for the analysis of p-aminophenol, a commonly used reagent in affinity sensing based on alkaline phosphatase.

Catalytic reduction of methylene blue by magnetite - silica composite

Iron oxide nanoparticle-based nanomaterials have well-known catalytic activity for the degradation of organic dyes in the water remediation process. The objective of this research was to synthesize iron oxide silica composite by sol-gel method and assess their applicability in wastewater treatment as a catalyst. Synthesized catalysts were characterized by FT-IR spectroscopy, X-ray diffractometry (XRD), and scanning electron microscopy (SEM). Vibration modes in FT-IR spectra show the presence of SiO2 and Fe-O bonds. The formation of Fe3O4 is shown by the XRD patterns. SEM images indicate that iron oxide particles and flakes are distributed in the silica matrix. The effects of catalyst dosage, temperature, the initial concentration of methylene blue (MB), NaBH4 concentration, foreign salts and ionic strength on MB degradation were studied. Maximum degradation of MB (99.89%) was obtained with an initial MB concentration of 20 mg dm-3, catalyst dose of 1.0 g dm-3, NaBH4 concentration of 6.25 mmol dm-3 and at a temperature of 50 °C. Common salts found in industrial wastewater such as NaCl, KCl, CaCl2, and MgCl2 inhibit the degradation of MB, while Na2SO4 enhances the degradation rate. Iron oxide helps in electron relay from BH4- to MB and silica tends to adsorb MB molecules and provide the proximity required for the catalytic reaction.