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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.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Optimum ultrasound duration for TiO2–water nanofluid is 150min.•Initial particle size is more effective than sonication time on stability.•Comparison with literature and statistical analysis provide ...useful conclusions.
Nanofluids are promising in many fields, including engineering and medicine. Stability deterioration may be a critical constraint for potential applications of nanofluids. Proper ultrasonication can improve the stability, and possibility of the safe use of nanofluids in different applications. In this study, stability properties of TiO2–H2O nanofluid for varying ultrasonication durations were tested. The nanofluids were prepared through two-step method; and electron microscopies, with particle size distribution and zeta potential analyses were conducted for the evaluation of their stability. Results showed the positive impact of ultrasonication on nanofluid dispersion properties up to some extent. Ultrasonication longer than 150min resulted in re-agglomeration of nanoparticles. Therefore, ultrasonication for 150min was the optimum period yielding highest stability. A regression analysis was also done in order to relate the average cluster size and ultrasonication time to zeta potential. It can be concluded that performing analytical imaging and colloidal property evaluation during and after the sample preparation leads to reliable insights.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Developing highly efficient and selective electrocatalysts for the CO2 reduction reaction to produce value‐added chemicals has been intensively pursued. We report a series of CuxOyCz nanostructured ...electrocatalysts derived from a Cu‐based MOF as porous self‐sacrificial template. Blending catalysts with polytetrafluoroethylene (PTFE) on gas diffusion electrodes (GDEs) suppressed the competitive hydrogen evolution reaction. 25 to 50 wt % teflonized GDEs exhibited a Faradaic efficiency of ≈54 % for C2+ products at −80 mA cm−2. The local OH− ions activity of PTFE‐modified GDEs was assessed by means of closely positioning a Pt‐nanoelectrode. A substantial increase in the OH−/H2O activity ratio due to the locally generated OH− ions at increasing current densities was determined irrespective of the PTFE amount.
A series of nanostructured CuxOyCz electrocatalysts were synthesized from Cu‐based MOF precursors. The catalysts were blended with PTFE for preparation of gas diffusion electrodes (GDEs) to suppress hydrogen evolution by preventing electrowetting process. The local OH− ion activities of working GDEs were determined in absence and presence of PTFE to exclude interference in local OH− ion generation in the vicinity of GDE by PTFE.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
NASICON-type solid electrolyte powders Li1.3Al0.3Ti1.7(PO4)3 (LATP) are synthesized by spray-drying and assisted sintering processes. The effects of different pH values of the spray-dried precursor ...solution on the crystallinity, morphology, ionic conductivity, compaction density and cycling stability of the LATP solid electrolyte sheets are investigated. The LATP-6.0 solid electrolyte sheets present the most perfect microstructure with a compaction density of 2.968 g cm−1 and the highest ionic conductivity of 1.182 E−4 S cm−1 with an activation energy of 0.273 eV at room temperature when the pH value of the precursor solution is adjusted to 6.0. Additionally, the assembled LiCoO2/LATP-6.0/Li all-solid-state coin cell delivers commendable cycling stability with a high discharge specific capacity of 150.5 mAh g−1 at 0.1 C after five activation cycles and retains a specific capacity retention rate of 94.28% after 300 cycles with various current densities at room temperature. Moreover, the LATP-6.0 solid electrolyte sheets maintain an intact morphology and uniformly-distributed elements composition after cycling. Based on these excellent results, the use of the LATP-6.0 sheets as solid electrolytes in high-performance all-solid-state lithium-ion batteries is a promising strategy.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•The change of metal ions induced by pH value was different.•Iron plaque was closely related to absorption and uptake of heavy metals.•The uptake of heavy metals showed a pH-dependent ...manner by regulating the expression of metal transporters.
The uptake of metal ions in soil depends primarily on the soil pH, but the effects of pH on individual heavy metals are not well understood. We found the effects of pH on rice uptake of heavy metals were quite different and the behavior of Zn and Cd were comparable, similar to Mn, but opposite of Fe. The concentration of Zn and Cd increased in plants when the pH was raised from 4.5 to 6.5, and then decreased at a pH of 7.5. Concentrations of Mn increased significantly when the pH was increased to 7.5. Iron plaque on root surfaces induced by high pH was likely related to the absorption and uptake of heavy metal elements, such as Cd and Zn, by the plant. Shoot Cd, Mn, and Zn concentrations were strongly positively correlated with DCB-extractable Cd (R2 = 0.98), Mn (R2 = 0.97), and Zn (R2 = 0.76) on the root surface. By contrast, Fe deposition on the root surface inhibited Fe uptake. Additionally, the pH-dependent expression of OsZIPs and OsNRAMPs affected metal uptake under different pH conditions, including OsZIP1, OsIRT1 and OsNRAMP5. Using a genetic approach that used Osnramp 5 mutants, we revealed the regulation of OsNRAMP 5 expression is the primary factor affecting the concentration of Cd and Mn in rice under different pH. Collectively, our research indicates that the uptake of heavy metals was regulated by pH-depended iron plaque formation and expression of metal transporter genes in rice.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The shelf life, storage stability and microbial changes of instant rice noodles (IRN) during storage were systematically investigated. The total aerobic viable count, mold and yeast counts of all ...samples increased gradually, and the shelf life of IRN sample with ε-polylysine hydrochloride (JL) preserved at 4 °C was significantly extended to 14 days. The pH value of sample with JL decreased gradually whereas the pH value of sample with citric acid (NM) increased slightly during storage. In IRN, molds displayed a greater spoilage potential than bacteria and yeasts. The 16S rDNA sequencing results indicated that preservatives, rather than temperature deduce to the significant differences of spoilage bacterial community among samples, and the NM considerably decreased the bacterial diversity internal transcribed spacer (ITS) region. rDNA sequencing results demonstrated that temperature was the critical factor in shaping fungal spoilage microbiota (Mantel test r = 0.16143, P < 0.05). Moreover, Spearman correlation analysis revealed that the abundance of partial microorganisms was significantly related to pH or temperature. The abundance of Achromobacter (r = −0.66276, P < 0.01), Delftia (r = −0.59983, P < 0.01), and Phyllobacterium (r = −0.55765, P < 0.01) were negatively correlated with pH. Additionally, the temperature was positively related to the relative abundance levels of Romboutsia (r = 0.517, P < 0.005), Arthrobacter (r = 0.446, P < 0.05), Bacillus (r = 0.551, P < 0.01), Bacteroides (r = 0.456, P < 0.05), and norank_f__JG30-KF-CM45 (r = 0.449, P < 0.05). These findings provided guiding information in selecting targeted preservatives and environmental condition for this innovative high moisture food.
•Quality and shelf-life of high-moisture instant rice noodles (IRN) is investigated.•Combination of ε-polylysine hydrochloride and 4 °C preserves the IRN effectively.•The dominant bacterial and fungal genera in spoiled IRN are reported.•Preservatives cause significant difference of bacterial microbiota among samples.•Temperature plays a major role in fungal community difference than preservatives.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Edible insects have become a recognized alternative and sustainable source of high-quality proteins and fats for livestock or human consumption. In the production process of black soldier fly (BSF), ...(Hermetia illucens L. Diptera: Stratiomyidae), initial substrate pH is a critical parameter to ensure the best value of insect biomass, life history traits, and quality bio-fertilizer. This study examined the impact of initial pH values on BSF larvae production, development time, and adult longevity. The BSF were reared on artificial diet with initial pH of 2.0, 4.0, 6.0, 8.0, and 10.0; the control was set at 7.0. Final BSF larval weight was significantly greater in substrates having initial pH 6.0 (0.21 g), control 7.0 (0.20 g), and 10.0 (0.20 g) with no significant difference among them, whereas larval weight reared with initial pH 2.0 and 4.0 were lowest at 0.16 g (−23%). Prepupal weight was greatest when larvae were reared on substrates with initial pH 6.0 (0.18 g), control 7.0 (0.19 g), 8.0 (0.18 g), and 10.0 (0.18 g). In contrast, the prepupal weight of larvae reared on diets with initial pH 2.0 was lowest at 0.15 g (−22%). Larval development time was 21.19 d at pH 8.0, about 3 d (12.5%) shorter than that of those reared on diets with initial pH 6.0, 7.0 control, and 10.0. In all treatments, pH shifted to 5.7 after 3–4 d and 8.5 after 16–17 d except for two groups (2.0 and 4.0) where the pH remained slightly acidic 5.0 and 6.5, respectively.
The chemical and mechanical stability of slag activated with two different concentrations of sodium sulfate (Na2SO4) after exposure to elevated temperatures ranging from 200 to 800°C with an ...increment of 200°C has been examined. Compressive strengths and pH of the hardened pastes before and after the exposure were determined. The various decomposition phases formed were identified using X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. The results indicated that Na2SO4 activated slag has a better resistance to the degradation caused by exposure to elevated temperature up to 600°C than Portland cement system as its relative strengths are superior. The finer slag and higher Na2SO4 concentration gave better temperature resistance. Whilst the pH of the hardened pastes decreased with an increase in temperature, it still maintained a sufficiently high pH for the protection of reinforcing bar against corrosion.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The present study reports the synthesis of cobalt ferrite nanoparticles (CoFe2O4 NPs) using the sol-gel precipitation process via mixing a stoichiometric ratio of cobalt chloride (1 M) and ferric ...chloride (2 M). The molar of ferric to cobalt was mentioned (2:1) and then 2 M of sodium hydroxide was added. The structural and morphological features of the material were assessed using X-ray diffraction (XRD), Scanning electron microscopy (SEM), and atomic force microscopy (AFM). The electrical properties were analyzed using an LCR meter, while the magnetic properties were measured using a vibrating sample magnetometer (VSM). Fourier-transform infrared spectroscopy (FTIR) investigated the material's molecular vibrations. The X-ray diffraction (XRD) analysis revealed that all the samples exhibited a cubic spinal structure, and no additional peak was detected. Interestingly, the average size of the crystallites (D) decreased from 17.74 nm to 16.58 nm as the pH level increased from 7 to 13. This finding provides important insights into the behaviour of the tested samples under different pH conditions. The formation of the ferrite spine was confirmed by FTIR spectroscopy, with the primary detected bands (408.92–470.65 cm−1) attributed to the octahedral complexes and (516.94–588.31 cm−1) assigned to the tetrahedral ones. The dielectric and imaginary part of the dielectric constant decreased with increasing pH values excluding samples prepared at pH = 11. All samples with different pH values exhibit resonance peaks at frequencies up to (1 KHz). The magnetic measurements carried out by the VSM instrument, the result show that the saturation magnetization increases with increasing pH and the higher saturation magnetization is 68 emu. g1.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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