The present study has investigated the influence of preparing conditions, including aging temperature and time, pH, and Tcalcination, on the co-precipitated ZnO–CuO–Al2O3–Cr2O3 mixed oxide at a ...high-temperature water gas shift reaction. XRD, BET, FTIR, TG-DTA, SEM, TEM, and H2-TPR were used to characterize the relationships between the synthesis parameters and the physicochemical features. The investigation proved that the activity in aging 5 h could be related to higher pore volume and lower crystalline size of 0.24 cm3g-1 and 6.4 nm, respectively. Also found that increasing the aging temperature to 60 °C results in a rise in the surface area and particle size of less than 6 nm, enhancing the catalyst activity. The findings showed that raising the Tcalcination reduced the surface area from 132 to 65 m2 g−1. It has been concluded that the CO conversion of 70 % was obtained when aged at 60 °C and calcination temperature of 400 °C.
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•The synthesis method affects the structural properties of the ZnO–CuO–Cr2O3–Al2O3 catalyst.•pH, ageing temperature and time have great influence on the structure of the catalyst.•The catalyst prepared by the optimum condition presented high activity and stability.
Schematic representation of BPA degradation with Co3O4-Bi2O3 by PMS activation in Co3O4-Bi2O3/PMS system, where BPA molecules were decomposed on the surface of Co3O4-Bi2O3 in the presence of PMS; ...meanwhile H2PO4− and CO32− in the system show the inhibited effects, NO3− and SO42− exhibit negligible effects, and Cl− shows a promoted effect, respectively.
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•Bisphenol A is fully degraded in Co3O4-Bi2O3/peroxymonosulfate system.•The effect of inorganic anions on the degradation efficiency of Bisphenol A was studied.•High Bisphenol A removal rate is due to SO4− and OH on the surface-bound of the catalyst.•Co3O4-Bi2O3/PMS system is effective in a broad pH range.
In this study, a novel Co3O4-Bi2O3 catalyst was synthesized using a microwave-assistant method, and the corresponding characteristics were studied through XRD, SEM, and N2 adsorption. As a peroxymonosulfate (PMS) activator, the catalytic activity of the synthesized catalyst was evaluated on Bisphenol A (BPA) removal, and the result showed that Co3O4-Bi2O3 catalyst promoted BPA degradation, where 100% BPA was degraded within 15 min under the condition of catalyst = 0.1 g·L−1 and PMS/BPAmolar = 5. The Co3O4-Bi2O3/PMS system presented a good catalytic activity when the solution pH varied from 3.0 to 11.0. Under the different concentrations of various inorganic anions in the Co3O4-Bi2O3/PMS system, Cl− showed an inhibited effect at low concentration and a promoted effect at high concentration. CO32− showed a slight inhibited effect, while H2PO4− showed a considerable inhibited effect. Additionally, both NO3− and SO42− showed a negligible effect on BPA removal. For the real water bodies, both the drinking water and tap water showed a slight decrease in degradation efficiency of BPA but a distinctly negative effect on BPA mineralization, which might be contributed to the competition between BPA and indigenous organic matters in the two water matrices for their oxidation by radical species. The quenching experiment was enforced and it was found that both SO4− and OH on the surface-bound of catalyst were the main active radicals in this system. Overall, the Co3O4-Bi2O3 catalyst as a PMS activator is a promising catalyst in PMS activation for sulfate radical-based wastewater treatment.
Soil salinization is a critical factor limiting growth and causing physiological dysfunction in plants. The damage from alkaline salt in most plants is significantly greater than that from neutral ...salt. However, there is still a lack of research on the action mechanism by which saline alkali stress on plants under the same salt concentration across different pH values. The present study examined the effects of different pH values (7.0, 8.0, 9.0, and 10.0) under the same salt concentration (200 mmolL−1) on photosynthetic function, photoprotective mechanism, nitrogen metabolism, and osmotic regulation in alfalfa (Medicago sativa) leaves, including a transcriptomic analysis of changes in gene expression related to the above metabolic processes. The results showed that low pH saline alkali stress (pH 7.0 and 8.0) promoted chlorophyll synthesis in alfalfa leaves, and non-photochemical quenching (NPQ) and cyclic electron transfer (CEF) were promoted. There was no significant effect on plant growth or photochemical activity. The soluble sugar, proline, and soluble protein contents did not change significantly, and there was no obvious oxidative damage in alfalfa leaves. However, when pH increased to 9.0 and 10.0, KEGG enrichment analysis showed that photosynthesis (map00195) and nitrogen metabolism (map00910) were significantly enriched (P < 0.05), and PSII antenna protein coding genes were down-regulated under pH 9.0 and 10.0 treatments. The activities of PSII and PSI were decreased under high pH saline alkali stress, and the expression levels of the photosynthetic electron transporter-related genes PetA, PetB, petE, and petF were also significantly down-regulated. PSII was more sensitive to high pH saline alkali stress than PSI, and the PSII receptor side was more sensitive to high pH saline alkali stress than the PSII donor side. The activities of the oxygen-evolving complex (OEC) and PSI were significantly damaged only at pH 10.0. The activities of nitrate reductase (NR) and nitrite reductase (NiR), the expression levels of their genes, and the content of soluble protein were also decreased under pH 9.0 and 10.0 treatments. The inhibition of plant growth and oxidative damage to alfalfa leaves caused by high pH saline alkali stress were mainly related to the inhibition of photosynthesis (light energy absorption, electron transfer) and nitrogen metabolism (NO3− reduction). Under high pH saline alkali stress (pH 10.0), the photoprotection mechanisms such as CEF and NPQ were inhibited, which was also one of the important reasons for photoinhibition in alfalfa leaves. The accumulation of osmotic adjustment substances, such as soluble sugar and proline, was an important mechanism by which alfalfa physiologically adapted to high pH alkaline salt stress.
•Low pH saline alkali stress promoted chlorophyll synthesis in alfalfa leaves, photoprotective mechanisms were activated.•As the pH value increased 9.0 and 10.0, photosynthetic electron transfer was blocked and oxidative damage occurred in leaves.•CEF and NPQ were inhibited, photosynthetic inhibition especially the OEC damaged under pH10.0 alkaline salt stress.•Accumulation of osmotic adjustment substances was an important mechanism by which alfalfa to saline alkali stress.
The effect of pH value at three levels (5, 7, and 9) and temperature at two levels (25 and 50ºC) on the sorption properties of chlorantraniliprole-CAP, dinotefuran-DNF, bispyribac-sodium-BPS, and ...metribuzin-MBZ were studied in calcareous soil. The sorption of CAP at pH 5 (38.2%) was significantly higher than that at pH 7 (32.4%) and 9 (28.4%), whereas the sorption of DNF at pH 5 was lower than that at pH 7. The adsorption of BPS at pH 9 was statistically significantly higher than that at pH 5 and pH 7. Regarding the herbicide MBZ adsorption percentages were 47.0, 61.1 and 57.1 % at pH 5, 7 and 9. The number of tested pesticides adsorbed by the soil was significantly influenced by the temperature. The adsorbed amount of CAP was decreased from 37% to 33% as the temperature was increased from 25˚C to 50 ˚C, while no significant differences of adsorbed DNF. Data showed that the adsorption of BPS and MBZ statistically decreases with temperature. The data from the adsorption behaviour of CAP, DNF, BPS, and MBZ in tested soil at different temperatures correspond well with the Freundlich isotherm. The negative ΔG˚ indicated that the adsorption of CAP, DNF, BPS, and MBZ were spontaneous at different temperatures. There was an increase in the entropy of the pesticide-soil systems as shown by the positive values of ΔS˚.
The designed electrocatalysts present excellent electrocatalytic performances for HER (19 mV, 80 mV, 20 mV), OER (252 mV, 316 mV, 211 mV), and overall water-splitting (1.53 V, 1.68 V, 1.47 V) in a ...wide pH values of 1 M KOH, 1 M PBS and 0.5 M H2SO4. Moreover, the overall water-splitting can be powered by renewable energy, including solar, wind and thermal energy.
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•The designed electrocatalysts exhibit ultralow overpotentials for HER and OER in all pH medias (pH = 0, 7, 14).•The assembled cell only needs a voltage of 1.47 V to afford 10 mA cm−2 for full water splitting in acidic media.•The overall water-splitting cell can work at high current densities.•Sustainable energies, such as solar, wind and biomass energies are utilized to drive water splitting using the prepared electrocatalysts.
Designing highly-efficient and pH-universal electrocatalysts for overall water-splitting reactions is important for the sustainable production of hydrogen. Herein, NiRu nanoparticles encapsulated into N-doped carbon (NiRu@NC) are fabricated with the assistance of MOF for hydrogen evolution reaction (HER) and also evolved into core–shell structured nanomaterials with abundant interfaces for oxygen evolution reaction (OER, Ni/RuOx@C). Benefiting from optimized electronic structure, interfacial synergy effect and special core–shell structure (~150 nm), the newly developed electrocatalysts present remarkable electrocatalytic activities with small overpotentials to drive 10 mA cm−2 for the HER (19 mV in alkaline, 80 mV in neutral, 20 mV in acid) and OER (252 mV, 316 mV, 211 mV). Moreover, the obtained electrocatalysts exhibit outstanding catalytic performances for overall water-splitting in a two-electrode system with 1.53 V and 1.67 V to drive 10 mA cm−2 in basic and neutral electrolyte, respectively. Remarkably, a small potential of 1.47 V is required to deliver 10 mA cm−2 in acidic media and no significant decay of the activity is observed. This work paves the way for designing a novel class of electrocatalyst that can not only exhibit remarkable electrocatalytic water splitting performances in various conditions, but also possess excellent stabilities for future generation of clean energy.
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•Double single atoms FeMo@CoNi-OH/Ni3S2 is obtained by in situ epitaxial growth.•FeMo@CoNi-OH/Ni3S2 shows high activity to HER in wide pH range and OER in alkaline.•Different ...electronegativity of Fe and Mo leads to charge rearrangement in catalyst.•The synergies between Fe and Mo enhances OWS performance of FeMo@CoNi-OH/Ni3S2.
The limitations of single-atom catalysts (SACs) hinder their application in wide-pH range of hydrogen evolution reaction (HER) and overall water-splitting in alkaline solution. Herein, we fabricate a rod-like Ni3S2 material wrapped by single-atom Fe-Mo co-modified CoNi-based nanosheets (FeMo@CoNi-OH/Ni3S2). The introduction of Fe-SAs and Mo-SAs into CoNi-hydroxyl compounds effectively changes their electronic structure and enhances their conductivity, thereby improving HER and OER performance. FeMo@CoNi-OH/Ni3S2 catalyst endows HER with overpotentials of 89, 176 and 177 mV in alkaline, acidic and neutral solutions, respectively, as well as good oxygen evolution reaction (OER) performance with 160 mV in alkaline to achieve 10 mA cm−2. The combination of the experiments and theoretical calculations reveals that the synergistic effect of Mo-SAs with Fe-SAs effectively reduces the intermediate energy barrier of the water dissociation step. This work contributes to the understanding of the catalytic mechanisms of dual single-atomic active sites in HER and OER processes.
The in vivo detection of small active molecules in plant tissues is essential for the development of precision agriculture. Tryptophan (Trp) is an important precursor material for auxin biosynthesis ...in plants, and the detection of Trp levels in plants is critical for regulating the plant growth process. In this study, an electrochemical plant sensor was fabricated by electrochemically depositing a polydopamine (PDA)/reduced graphene oxide (RGO)-MnO2 nanocomposite onto a glassy carbon electrode (GCE). PDA/RGO-MnO2/GCE exhibited high electrocatalytic activity for the oxidation of Trp owing to the combined selectivity of PDA and catalytic activity of RGO-MnO2. To address the pH variability of plants, a reliable Trp detection program was proposed for selecting an appropriate quantitative detection model for the pH of the plant or plant tissue of interest. Therefore, a series of linear regression curves was constructed in the pH range of 4.0–7.0 using the PDA/RGO-MnO2/GCE-based sensor. In this pH range, the linear detection range of Trp was 1–300 μM, the sensitivity was 0.39–1.66 μA μM−1, and the detection limit was 0.22–0.39 μM. Moreover, the practical applicability of the PDA/RGO-MnO2/GCE-based sensor was successfully demonstrated by determining Trp in tomato fruit and juice. This sensor stably and reliably detected Trp levels in tomatoes in vitro and in vivo, demonstrating the feasibility of this research strategy for the development of electrochemical sensors for measurements in various plant tissues.
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•An electrochemical sensor detects tryptophan (Trp) in vivo and in vitro.•Trp selectively adsorbed by polydopamine is efficiently electro-oxidized by RGO-MnO2.•Linear regression models at pH 4–7 are suitable for the variable pH of plants.•The in situ detection of free Trp levels is achieved in tomato fruit and juice.•The Trp levels determined in vivo and in vitro are correlated.
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•Preparation parameters in sol-gel formation and combustion processes were studied.•Citric acid/calcium nitrate ratio influenced the sol-gel formation.•NH4NO3 and Ca-based precipitate ...destroyed sol-gel structure when pH was over 3.•Lower ignition temperature and higher heating rate facilitated better performance.
The sol-gel combustion synthesis is a superior method to prepare high-performance CaO-based sorbent which is applicable for flue gas decarbonization and thermochemical energy storage. To optimize this synthesis, this study investigated different preparation variables in the sol-gel formation process and combustion process. The effects of these variables on the cyclic CO2 sorption performance, micromorphology, and physical parameters of the prepared pure CaO sorbents were studied. First, worse cyclic performance was shown when the H2O/Ca2+ molar ratio was over 100:1, and the optimal ratio was 80:1. Second, the citric acid/calcium nitrate ratio influenced the formation of the complex as well as the gas production and adiabatic flame temperature in the combustion process, and the optimal molar ratio was 1:1. Third, the NH4NO3 and Ca-based precipitate would be produced when the pH value of the precursor solution was over 3. The optimal pH value was 2, and the carbonation conversion of the prepared sorbent reached 99% in the 2nd cycle within the 10 min carbonation at 650 °C under 15% volume CO2. After 20 cycles, the conversion was 70.4%. Fourth, a higher heating rate facilitated better cyclic performance and the optimal heating rate was 10 °C/min. Finally, a higher initial ignition temperature accelerated grain growth and particles agglomeration of the combustion product, and the optimal temperature was 300 °C.
The degradation of material induced by sulfate attack is major durability problem facing cementitious materials. In this paper, to illustrate the nanoscale chemical degradation, Portland cement ...samples were exposed to 5 wt% NaSO4 solution with different pH values (pH = 13, 8 and 5) as the function of corrosion ages (28 and 180 days). The effects of pH value on the hydrate phase, morphology and microstructure of cement hydration products under sulfate attack were characterized in combination with XRD, SEM-EDS, 1H, 27Al and 29Si NMR. The results demonstrate that reducing pH value of sulfate solution facilitates the formation and precipitation of columnar and platelet gypsum crystals in cement paste, whereas inhibiting the ettringite formation. A slight increase in the proportion of deleterious micropores larger than 1.6 μm as the sample exposed to sulfate with low pH value. The ettringite induced by sulfate attacking is transformed to AFm at early period and reversal transformation happens at later period. Reduction of the pH value of sulfate solution accelerates the transformation reaction of the hexa-coordinated aluminate phases. 29Si NMR test revealed that with pH reducing from 13 to 5, the hydration degree increase nearly 18%, the mean silicate chain length increase by 66.2% and Al4/Si ratio increase by nearly 30%. Also, the silicate polymerization enhancement is closely related with Al3+ ions extraction at early sulfate-attack period and re-entering at late sulfate-attack period. This research might provide nanoscale insights to guide more durable cement-based material in detrimental environment.
This paper explores a hybrid- and two mono-nanofluids and, to be more specific, it deals with the effect of adding Silica (SiO2) and Graphene (G) nanoparticles and their hybrid (G (30%) + SiO2 (70%)) ...on viscosity of water. For all designed hybrid- and mono-nanofluids at various concentrations of 0.05–1%, viscosity was measured under the influence of temperature (25–50 °C). Meanwhile, for measuring the viscosity, different shear rates (12.23–122.3 s−1) have been applied to evaluate rheological behavior of nanofluids. The viscosity of hybrid nanofluids lies between the viscosity of mono nanofluids, while G/Water mono-nanofluid samples have the highest value. Experimental results revealed non-Newtonian pseudoplastic behavior for all three types of nanofluids, this behavior is more evident in the G/Water mono-nanofluid. Moreover, G-SiO2(30–70%)/Water hybrid nanofluid has a higher tendency to the behavior of SiO2/Water mono-nanofluid. Finally, via curve fitting method, two-variable correlations were proposed to estimate rheological behavior of G-SiO2(30–70%)/Water hybrid nanofluid.
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•Preparing novel nanofluids by adding Graphene and Silica nano-powders in distilled water•Performing characterization tests such as XRD, DLS, Raman and FESEM•Using chemical and physical methods to homogenize and stabilize nanofluid samples•Measuring viscosity for various concentrations under different shear rates and temperatures•Comparing the rheological behavior of hybrid- and mono-nanofluids
